Academic literature on the topic 'Plasmid resistance'
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Journal articles on the topic "Plasmid resistance"
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Ling, J. M., P. C. Shaw, K. M. Kam, A. F. Cheng, and G. L. French. "Molecular studies of plasmids of multiply-resistantShigellaspp. in Hong Kong." Epidemiology and Infection 110, no. 3 (June 1993): 437–46. http://dx.doi.org/10.1017/s095026880005086x.
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SUMMARYOne hundred and twoShigellaspp. isolated in two hospitals in Hong Kong were analysed for antibiotic resistances, resistance plasmids and plasmid profiles. Three quarters of the isolates wereS.flexneri. All isolates harboured plasmids, up to a maximum of ten within one strain. Plasmids of 220 kb encoding resistances to tetracycline, chloramphenicol and sulphonamide and probably also associated with invasivenes in the Sereny test were found in 80 strains and were transferable in 18% of cases. Resistance plasmids of 92 and 99 kb were found in 27 and 15 strains respectively and encoded resistances to ampicillin, tetracycline, chloramphenicol, kanamycin, sulphonamide, trimethoprim, cotrimoxazole and gentamicin; these plasmids were usually transferable. Four plasmids of 3·9, 2·8, 2·2 and 1·8 kb were commonly found inS. flexneristrains, but were rare in other species. In contrast, there was no predominant plasmid profile inS. sonnei. S. flexneriis endemic in Hong Kong and these plasmid studies suggest that the strains in circulation are derived from only a few clones.
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Jalasvuori, Matti, Ville-Petri Friman, Anne Nieminen, Jaana K. H. Bamford, and Angus Buckling. "Bacteriophage selection against a plasmid-encoded sex apparatus leads to the loss of antibiotic-resistance plasmids." Biology Letters 7, no. 6 (June 2011): 902–5. http://dx.doi.org/10.1098/rsbl.2011.0384.
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Antibiotic-resistance genes are often carried by conjugative plasmids, which spread within and between bacterial species. It has long been recognized that some viruses of bacteria (bacteriophage; phage) have evolved to infect and kill plasmid-harbouring cells. This raises a question: can phages cause the loss of plasmid-associated antibiotic resistance by selecting for plasmid-free bacteria, or can bacteria or plasmids evolve resistance to phages in other ways? Here, we show that multiple antibiotic-resistance genes containing plasmids are stably maintained in both Escherichia coli and Salmonella enterica in the absence of phages, while plasmid-dependent phage PRD1 causes a dramatic reduction in the frequency of antibiotic-resistant bacteria. The loss of antibiotic resistance in cells initially harbouring RP4 plasmid was shown to result from evolution of phage resistance where bacterial cells expelled their plasmid (and hence the suitable receptor for phages). Phages also selected for a low frequency of plasmid-containing, phage-resistant bacteria, presumably as a result of modification of the plasmid-encoded receptor. However, these double-resistant mutants had a growth cost compared with phage-resistant but antibiotic-susceptible mutants and were unable to conjugate. These results suggest that bacteriophages could play a significant role in restricting the spread of plasmid-encoded antibiotic resistance.
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Erac, Bayri, Fethiye Ferda Yilmaz, Ismail Ozturk, Sabire Sohret Aydemir, and Mine Hosgor-Limoncu. "Analyses of Plasmids Harbouring Quinolone Resistance Determinants in Enterobacteriaceae Members." Polish Journal of Microbiology 66, no. 4 (December 4, 2017): 529–32. http://dx.doi.org/10.5604/01.3001.0010.7084.
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The aim of this study was to explore the plasmid characteristics of eight clinical Enterobacteriaceae strains containing extended broad spectrum beta-lactamases and plasmid-mediated quinolone resistance. Plasmids were transferred by conjugation or transformation and resistance determinants were investigated by PCR. We showed that at least one plasmid harbouring qnrB or qnrS determinant was transferred by conjugation in five isolates. QepA determinant was confirmed to be on a non-conjugative plasmid. We found at least one beta-lactamase gene in seven of the eight clinical isolates having plasmid-mediated quinolone resistance, which indicated that these two resistance determinants were mostly on the same conjugative plasmids.
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Hernández-Mendoza, Armando, Rosalba Salgado-Morales, Abimael Morán-Vázquez, David López-Torres, Blanca Inés García-Gómez, and Edgar Dantán-González. "Molecular Characterization of pBOq-IncQ and pBOq-95LK Plasmids of Escherichia coli BOq 01, a New Isolated Strain from Poultry Farming, Involved in Antibiotic Resistance." Microorganisms 10, no. 8 (July 26, 2022): 1509. http://dx.doi.org/10.3390/microorganisms10081509.
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The increase in antimicrobial resistance has raised questions about how to use these drugs safely, especially in veterinary medicine, animal nutrition, and agriculture. Escherichia coli is an important human and animal pathogen that frequently contains plasmids carrying antibiotic resistance genes. Extra chromosomal elements are required for various functions or conditions in microorganisms. Several phage-like plasmids have been identified, which are important in antibiotic resistance. In this work, the molecular characterization of the pBOq-IncQ (4.5 kb) and pBOq-95LK (95 kb) plasmids found in the E. coli strain BOq 01, a multidrug resistant bacteria isolated from a poultry farm, are considered. Plasmid pBOq-IncQ belongs to the incQ incompatibility plasmid family and is involved in sulfonamide resistance. Plasmid pBOq-95LK is a lytic phage-like plasmid that is involved in the lysis of the E. coli BOq 01 strain and carries a bleomycin resistance gene and a strain cured of this plasmid shows bleomycin sensitivity. Induction of the lytic cycle indicates that this phage-like plasmid is an active phage. This type of plasmid has been reported to acquire genes such as mcr-1, which codes for colistin resistance and bacterial persistence and is a significant public health threat. A genome comparison, a pangenomic and phylogenomic analysis with other phage-like plasmids reported in the literature were performed to understand better the evolution of this kind of plasmid in bacteria and its potential importance in antibiotic resistance.
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Hoshino, Takayuki, Takayuki Ikeda, Hiroyuki Narushima, and Noboru Tomizuka. "Isolation and characterization of antibiotic-resistance plasmids in thermophilic bacilli." Canadian Journal of Microbiology 31, no. 4 (April 1, 1985): 339–45. http://dx.doi.org/10.1139/m85-065.
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Four antibiotic-resistance plasmids isolated from thermophilic bacilli were characterized in detail. Three tetracycline-resistance (Tcr) plasmids were designated as pTHT9 (7.7 kilobases (kb)), pTHT15 (4.5 kb) and pTHT22 (8.4 kb). From the results of restriction endonuclease analysis and the subsequent Southern hybridization, these were found to possess extensive genetic homology in the regions that include the replication origin and the Tcr gene. Detailed restriction maps of the smallest Tcr plasmid pTHT15 and a kanamycin-resistance (Kmr) plasmid pTHN1 (4.8 kb) were constructed. The positions of antibiotic-resistance loci and regions essential for plasmid replication were determined by cloning plasmid fragments in Bacillus subtilis. These four plasmids were found to replicate and express the resistance genes stably in both B. subtilis and B. stearothermophilus.
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Bottery, Michael J., A. Jamie Wood, and Michael A. Brockhurst. "Selective Conditions for a Multidrug Resistance Plasmid Depend on the Sociality of Antibiotic Resistance." Antimicrobial Agents and Chemotherapy 60, no. 4 (January 19, 2016): 2524–27. http://dx.doi.org/10.1128/aac.02441-15.
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ABSTRACTMultidrug resistance (MDR) plasmids frequently carry antibiotic resistance genes conferring qualitatively different mechanisms of resistance. We show here that the antibiotic concentrations selecting for the RK2 plasmid inEscherichia colidepend upon the sociality of the drug resistance: the selection for selfish drug resistance (efflux pump) occurred at very low drug concentrations, just 1.3% of the MIC of the plasmid-free antibiotic-sensitive strain, whereas selection for cooperative drug resistance (modifying enzyme) occurred at drug concentrations exceeding the MIC of the plasmid-free strain.
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Fricke, W. Florian, Timothy J. Welch, Patrick F. McDermott, Mark K. Mammel, J. Eugene LeClerc, David G. White, Thomas A. Cebula, and Jacques Ravel. "Comparative Genomics of the IncA/C Multidrug Resistance Plasmid Family." Journal of Bacteriology 191, no. 15 (May 29, 2009): 4750–57. http://dx.doi.org/10.1128/jb.00189-09.
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ABSTRACT Multidrug resistance (MDR) plasmids belonging to the IncA/C plasmid family are widely distributed among Salmonella and other enterobacterial isolates from agricultural sources and have, at least once, also been identified in a drug-resistant Yersinia pestis isolate (IP275) from Madagascar. Here, we present the complete plasmid sequences of the IncA/C reference plasmid pRA1 (143,963 bp), isolated in 1971 from the fish pathogen Aeromonas hydrophila, and of the cryptic IncA/C plasmid pRAx (49,763 bp), isolated from Escherichia coli transconjugant D7-3, which was obtained through pRA1 transfer in 1980. Using comparative sequence analysis of pRA1 and pRAx with recent members of the IncA/C plasmid family, we show that both plasmids provide novel insights into the evolution of the IncA/C MDR plasmid family and the minimal machinery necessary for stable IncA/C plasmid maintenance. Our results indicate that recent members of the IncA/C plasmid family evolved from a common ancestor, similar in composition to pRA1, through stepwise integration of horizontally acquired resistance gene arrays into a conserved plasmid backbone. Phylogenetic comparisons predict type IV secretion-like conjugative transfer operons encoded on the shared plasmid backbones to be closely related to a group of integrating conjugative elements, which use conjugative transfer for horizontal propagation but stably integrate into the host chromosome during vegetative growth. A hipAB toxin-antitoxin gene cluster found on pRA1, which in Escherichia coli is involved in the formation of persister cell subpopulations, suggests persistence as an early broad-spectrum antimicrobial resistance mechanism in the evolution of IncA/C resistance plasmids.
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Lim, Suk-Kyung, Koichi Tanimoto, Haruyoshi Tomita, and Yasuyoshi Ike. "Pheromone-Responsive Conjugative Vancomycin Resistance Plasmids in Enterococcus faecalis Isolates from Humans and Chicken Feces." Applied and Environmental Microbiology 72, no. 10 (October 2006): 6544–53. http://dx.doi.org/10.1128/aem.00749-06.
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ABSTRACT The drug resistances and plasmid contents of a total of 85 vancomycin-resistant enterococcus (VRE) strains that had been isolated in Korea were examined. Fifty-four of the strains originated from samples of chicken feces, and 31 were isolated from hospital patients in Korea. Enterococcus faecalis KV1 and KV2, which had been isolated from a patient and a sample of chicken feces, respectively, were found to carry the plasmids pSL1 and pSL2, respectively. The plasmids transferred resistances to vancomycin, gentamicin, kanamycin, streptomycin, and erythromycin to E. faecalis strains at a high frequency of about 10−3 per donor cell during 4 hours of broth mating. E. faecalis strains containing each of the pSL plasmids formed clumps after 2 hours of incubation in broth containing E. faecalis FA2-2 culture filtrate (i.e., the E. faecalis sex pheromone), and the plasmid subsequently transferred to the recipient strain in a 10-min short mating in broth, indicating that the plasmids are responsive to E. faecalis pheromones. The pSL plasmids did not respond to any of synthetic pheromones for the previously characterized plasmids. The pheromone specific for pSL plasmids has been designated cSL1. Southern hybridization analysis showed that specific FspI fragments from each of the pSL plasmids hybridized with the aggregation substance gene (asa1) of the pheromone-responsive plasmid pAD1, indicating that the plasmids had a gene homologous to asa1. The restriction maps of the plasmids were identical, and the size of the plasmids was estimated to be 128.1 kb. The plasmids carried five drug resistance determinants for vanA, ermB, aph(3′), aph(6′), and aac(6′)/aph(2′), which encode resistance to vancomycin, erythromycin, kanamycin, streptomycin, and gentamicin/kanamycin, respectively. Nucleotide sequence analyses of the drug resistance determinants and their flanking regions are described in this report. The results described provide evidence for the exchange of genetic information between human and animal (chicken) VRE reservoirs and suggest the potential for horizontal transmission of multiple drug resistance, including vancomycin resistance, between farm animals and humans via a pheromone-responsive conjugative plasmid.
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Giles, Janice S., Harry Hariharan, and Susan B. Heaney. "The plasmid profiles of fish pathogenic isolates of Aeromonas salmomcida, Vibrio anguillarum, and Vibrio ordalii from the Atlantic and Pacific coasts of Canada." Canadian Journal of Microbiology 41, no. 3 (March 1, 1995): 209–16. http://dx.doi.org/10.1139/m95-029.
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The plasmid profiles of oxytetracycline- and streptomycin-resistant isolates of Aeromonas salmonicida, Vibrio anguillarum, and Vibrio ordalii were examined by agarose gel electrophoresis. Bacterial isolates were from disease outbreaks in fish on the Atlantic and Pacific coasts. Resistant isolates were examined when grown in the presence and absence of antibiotic. Alkaline lysis methods were used for plasmid isolation. Vibrio spp. were predominantly plasmidless, except for a 47-kilobase (kb) plasmid. Atlantic coast isolates of A. salmonicida possessed four or six plasmids, with four smaller plasmids ranging in size from 4.3 to 8.1 kb being consistently observed. The plasmid profiles of antibiotic-sensitive ATCC strains were identical. The plasmid profiles of the Pacific coast isolates of A. salmonicida varied slightly from those of the Atlantic coast isolates with six plasmids observed, ranging in size from 4.2 to 8.9 kb. Resistance to the antibiotics was not altered following plasmid curing experiments and resistance was not transferable to Escherichia coli. Thus, resistance to oxytetracycline and streptomycin did not appear to be plasmid mediated.Key words: plasmids, antibiotics, Aeromonas, Vibrio, fish.
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Tonin, Patricia N., and Robert B. Grant. "Genetic and physical characterization of trimethoprim resistance plasmids from Shigella sonnei and Shigella flexneri." Canadian Journal of Microbiology 33, no. 10 (October 1, 1987): 905–13. http://dx.doi.org/10.1139/m87-157.
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Analysis of six Shigella flexneri and four S. sonnei isolates with trimethoprim (Tp) resistance from clinical cases in Ontario has shown that, in all isolates, the Tp resistance is mediated by gene(s) on conjugative, multiple antibiotic-resistance plasmids. The physical and genetic characterization of these plasmids revealed that there are three different Tp resistance plasmids. One group, composed of all six S. flexneri plasmids, consists of plasmids which are about 70 megadaltons (MDa) and inhibit the fertility of an Escherichia coli Hfr strain (Fi+). A representative member of this group, pPT4, demonstrates a weak incompatibility reaction with IncFI plasmid R455-2. Another group, three of the four S. sonnei plasmids, contains plasmids which are about 43 MDa, Fi−, and mediate propagation of phage PRD1. The third group, the remaining S. sonnei plasmid, is 53 MDa,fi+, mediates propagation of phages fd and MS2, and is incompatible with IncFII plasmid R100. These plasmids also have been differentiated by restriction endonuclease fragment profiles. Analysis of pPT4 has revealed that the Tp resistance of this plasmid is transposable. The transposon, Tn536, is different from previously described Tp resistance transposons; it is 16 MDa, and in addition to Tp, it encodes resistance to mercuric chloride ions, spectinomycin, streptomycin, and sulfonamides.
Dissertations / Theses on the topic "Plasmid resistance"
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Udo, Edet Ekpenyong. "Characterisation and molecular studies of plasmids from Nigerian staphylococci." Thesis, Curtin University, 1991. http://hdl.handle.net/20.500.11937/1845.
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Fifty three Staphylococcus aureus isolates were obtained from three centres, two hospitals and a private pathology laboratory, and studied for susceptibility to bacteriophages, resistance to antimicrobial agents and plasmid contents.Results of bacteriophage typing revealed that they belonged to a variety of phage types. Eighteen were untypable by any of the International Set of Phages, 16 belonged to phage group 111, nine to group I, four to group 11, two to group IV and two to the miscellaneous group.The isolates were resistant to one or more of methicillin (Mc), benzyl penicillin (Pc), gentamicin (Gm) , kanamycin (Km) , neomycin (Nm) , streptomycin (Sm) , trimethoprim (Tp), sulphonamides (Su), tetracycline (Tc), minocycline (Mn), chloramphenicol (Cm), novobiocin (Nb) and fusidic acid (Fa). Resistance to Pc was due to the production of beta-lactamase (Bla). No resistance to vancomycin, spectinomycin and erythromycin was detected. Resistance was also found to heavy metals such as cadmium (Cd), mercury (Hg), phenyl mercuric acetate (Pma), arsenate (Asa) and to the nucleic-acid binding compounds propamidine isethionate (Pi) and ethidium bromide (Eb).All but one of the isolates harboured plasmids. The number of plasmids the isolates carried varied from one to six and their sizes ranged from < 1.0 kb to c.48 kb.Location of the resistance determinants was ascertained by curing and transfer experiments. Loss of resistance was tested after growth at 43.5°C and transfer of resistance determinants was attempted by transduction, mixed-culture transfer and conjugation. The results revealed that resistance to Mc, Gm, Tp, Mn and Fa was chromosomal in all the resistant isolates and in some isolates Bla and resistance to Sm and Cd were chromosomal as well as plasmid encoded. In the majority of cases Bla and resistance to Km, Nm, Sm, Tc, Cin, Cd, Hg, Asa, Pma, Pi and Eb was encoded by plasmids.Conjugation experiments led to the isolation of three unique conjugative plasmids which have not been found to confer resistance to antimicrobials or to produce haemolysins or diffusible pigment (Dip). The three plasmids, pWBG620, pWBG637 and pWBG661, were indistinguishable by restriction endonuclease analysis and DNA-DNA hybridisation. However pWBG620, unlike pWBG637 and pWBG661, was not detected in the cytoplasm of its host and was only detected in transconjugants after it mobilised a non-conjugative Sm-resistance (SmR) plasmid. Further analysis indicated that it is integrated into the chromosome of its host, excises during conjugation and mobilises the SmR plasmid.These plasmids were studied further using pWBG637 as a representative. It was compared with representatives of the two groups of conjugative plasmids which have been reported in the staphylococci. These are the plasmids which encode resistance to Gm, Km and Nm and those which code for the production of diffusible pigment. The three types of conjugative plasmids were compared by restriction endonuclease analysis and DNA- DNA hybridisation and were found to be different. A preliminary restriction map of pWBG637 has also been constructed.However since pWBG637 has no resistance phenotype direct selection for it was not possible in transfer experiments and for incompatibility (Inc.). To study it further it was necessary to construct resistant derivatives which could be selected for in transfer experiments. This was achieved by labelling pWBG637 with resistance transposons to generate two conjugative plasmids, pWBG636 carrying an insert of Tn3851 (Gm- resistance) and pWBG642 carrying an insert of Tn551 (hn- resistance). It was found that transposon labelling had not changed the incompatibility of pWBG637 and therefore pWBG636 and pWBG642 were used in further experiments in place of pWBG637. Inc. tests with the pWBG637 derivatives revealed that the pWBG637 type of plasmid is not only different from the other two types of conjugative plasmids but is different from any of the described staphylococcal Inc. groups and therefore the pWBG637 type of plasmids represent a new Inc. group 15. The pWBG637 type of plasmids were studied further using plasmids pWBG636 and pWBG642. They were able to transfer conjugatively to a capsulated S.aureus strain either by the polyethylene glycol method or on filter membranes. They also transferred by conjugation to S. epidermidis and Streptococcus faecalis and were able to transfer back from these strains to S.aureus indicating that they also replicate in these hosts. Consequently they have been used to mobilise non-conjugative plasmids from S.epidermidis and non phage typable S.aureus. Both plasmids failed to transfer conjugatively to Bacillus subtilis and Escherichia coli.pWBG637 transferred non-conjugative plasmids by mobilising them in a manner similar to mobilisation (donation) in E.coli or by recombining with them to form new resistance plasmids. In one case, pWBG628 which encodes Bla and resistance to Cd, Km, Nm and Sm and has no homology with pWBG637 recombined with it during conjugation to produce three new conjugative plasmids pWBG629, pWBG630 and pWBG631 carrying resistance determinants from pWBG628. One of these plasmids, pWBG629, was found to be pWBG637 which had acquired a 4.5 kb element encoding resistance to Km, Nm and Sm. This element was shown to be transposable in both rec+ and rec- backgrounds and has been designated Tn3854. It expressed Sm resistance in E.coli and differs on this account from the Gram-negative transposon Tn5 which expresses resistance to Km, Nm and Sm in non-enteric bacteria but only resistance to Km and Nm in E. coli.Where possible the non-conjugative plasmids encoding resistance to antimicrobial agents were compared with phenotypically similar plasmids isolated from other parts of the world. It was found that the Tc and Sm resistance plasmids were closely related to other plasmids with the same phenotype whereas the Cm resistance plasmids were different.Although the majority of the Bla plasmids belonged to Inc. group 1 they demonstrated significant restriction enzyme fragment length polymorphism when compared with other Bla plasmids.This study has provided the first data on the genetics of antimicrobial resistance in Nigerian S.aureus. Although many of the plasmids studied were found to be similar to those previously described the isolates also contained some unique and previously undescribed plasmids.
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BERTINI, ALESSIA. "Plasmid-mediated antimicrobial resistance in Gram-negative bacteria." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/641.
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L’epidemiologia dei plasmidi di resistenza è il principale mezzo per descrivere la diffusione
delle resistenze agli antimicrobici. L’identificazione di plasmidi correlati associati a specifici geni di
resistenza può aiutare a tracciare la disseminazione di plasmidi epidemici, aprendo nuovi scenari
epidemiologici sui meccanismi di diffusione delle resistenze agli antimicrobici. Questo aspetto è
particolarmente evidente quando si considerano plasmidi che sono associati alla diffusione delle
Beta Lattamasi a Spettro Esteso (ESBL) come gli enzimi CTX-M, SHV, TEM.
Lo scopo di questa tesi è stato quello di caratterizzare plasmidi che conferiscono resistenza
a farmaci rilevanti per la terapia umana in differenti collezioni di Enterobacteriaceae di origine
umana e animale. Verranno discussi diversi esempi di plasmidi epidemici quali: i plasmidi
IncHI2 che trasportano i geni blaCTX-M-9 o blaCTX-M-2 provenienti da isolati di origine
umana e animale di Escherichia coli e Salmonella dalla Spagna, Belgio e Inghilterra; i plasmidi
IncI1 caratterizzati da specifici fattori di virulenza, che trasportano i geni blaTEM-52 e
blaCTX-M-1 derivanti da isolati di Salmonella e E. coli di origine umana e animale; i plasmidi
IncN che trasportano i geni codificanti la metallo-β-lattamasi VIM-1 da isolati umani di
Klebsiella pneumoniae and E. coli dalla Grecia; plasmidi IncA/C2 associati a specifici geni di
resistenza come blaCMY-2, blaCMY-4, blaVIM-4 e blaVEB-1 provenienti da diverse
Enterobacteriaceae isolate in differenti parti del mondo, ed infine, i plasmidi associati all’enzima
SHV-12 isolati in diverse Enterobacteriaceae di origine umana e animale.
L’analisi mediante comparazione della struttura plasmidica ha permesso di rilevare la diffusione
di plasmidi emergenti e consente di tracciare i percorsi evolutivi e di diffusione attraverso l’acquisizione
di una vastità di elementi genetici mobili associati ai geni di resistenza.The epidemiology of resistance plasmids is a major issue for the description of antimicrobial resistance diffusion. The identification of related plasmids associated to specific resistance genes may help to follow the spread of epidemic plasmids, opening new epidemiological scenarios on the mechanism of diffusion of antimicrobial resistance. This aspect is particularly interesting when applied to collections of plasmids that are playing a major role in the diffusions of Extended Spectrum Beta Lactamases (ESBLs) such as CTX-M, SHV, TEM. The aim of this thesis is the molecular characterization of plasmids conferring drug resistances in different collections of Enterobacteriaceae of human and animal origin. Several example of epidemic plasmids will be discussed: the IncHI2 plasmids carrying blaCTX-M-9 or blaCTX-M-2 genes identified from human and animal isolates of Escherichia coli and Salmonella from Spain, Belgium and UK; the IncI1 family of plasmids characterized by specific virulence factors, carrying the blaCMY-2, blaTEM-52 and blaCTX-M-1 genes from Salmonella and E. coli of human and animal origin; the IncN plasmids carrying the gene codifying the metallo-β-lacatamase VIM-1 from human isolates of Klebsiella pneumoniae and E. coli in Greece; the IncA/C2 plasmids carrying specific resistance genes such as blaCMY-2, blaCMY-4, blaVIM-4 and blaVEB-1 from different Enterobacteriaceae isolated worldwide; different plasmid replicons (IncFII, IncA/C1, IncI1) carrying the ESBL SHV-12 from human and animal origin. The comparative analysis of plasmid backbones allowed to ascertain the diffusion of common, emerging plasmids and helped to determine the evolution of these plasmids by acquisition of relevant resistance genes by a panoply of mobile genetic elements and illegitimate recombination events.
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Chan, Helena. "Characterisation of a plasmid segregational stability determinant, par, of the staphylococcal multiresistance plasmid, pSK1." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17714.
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Staphylococcus aureus is a bacterium that is a common cause of hospital-acquired infections that is also becoming a significant cause of serious community-acquired infections. Many clinical strains of S. aureus carry extrachromosomal DNA elements called plasmids, which often encode genes conferring antimicrobial resistance. Plasmid segregation mechanisms such as active partitioning systems ensure that low copy-number plasmids are accurately segregated and inherited by progeny cells upon division, even in the absence of selection. The staphylococcal multiresistance plasmid, pSK1, contains a gene, par, which enhances the efficiency of plasmid inheritance, possibly via an active plasmid partitioning system. Active plasmid partitioning systems characterised thus far encode two individual proteins – a DNA-binding protein and a force-generating NTPase protein. Although the pSK1 par system is widespread among non-conjugative staphylococcal plasmids, it differs from characterised plasmid partitioning systems by encoding only a single protein, Par. Previous studies have shown that pSK1 Par exhibits both DNA-binding and multimerisation activities that are common to characterised partitioning proteins. Much remains to be elucidated about the mechanism by which pSK1 par facilitates efficient plasmid inheritance. This knowledge gap will be addressed by this experiments described in this thesis, which aim to 1) determine the functional significance the predicted Par domains, particularly the disordered C-terminal domain, 2) identify any host factors that interact with Par, and 3) determine the localisation of Par and plasmid DNA during plasmid segregation in S. aureus. These experiments are designed to provide a broader understanding of the mechanism of par-mediated plasmid inheritance, and provide greater insight into possible methods of disrupting the spread and maintenance of antimicrobial resistance plasmids.
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Bottery, Michael J. "The sociality and evolution of plasmid-mediated antimicrobial resistance." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/19016/.
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Overuse and misuse of antibiotics has led to the global spread of antimicrobial resistance, threatening our ability to treat bacterial infections. The horizontal acquisition of multidrug resistance (MDR) plasmids, from other bacterial lineages, has been instrumental in spreading resistance. Newly acquired plasmids are often poorly adapted to hosts causing intragenomic conflicts, reducing the competitiveness of plasmid-carrying strains. Costs can be overcome by positive selection for plasmid-encoded adaptive traits in the short-term, or ameliorated by compensatory evolution in the long-term. How the selection and adaptation of MDR plasmids varies with antibiotic treatment remains unclear. First, I demonstrate that the selective conditions for the maintenance of an MDR plasmid are dependent upon the sociality of resistance it encodes. Selection for efflux of antibiotics, a selfish trait, occurred at very low concentrations of antibiotic, far below the minimum inhibitory concentration of sensitive plasmid-free strain. In contrast, selection for inactivation of antibiotics, a cooperative trait, increased the amount of antibiotic required to select for the MDR plasmid, allowing sensitive plasmid-free bacteria to survive high levels of antibiotic. These selection dynamics were only accurately predicted when mathematical models included the mechanistic details of antibiotic resistance. Secondly, I show that the trajectory of evolution following MDR plasmid acquisition varies with antibiotic treatment. Tetracycline treatment favoured a distinct coevolutionary trajectory of chromosomal resistance mutations coupled with plasmid mutations impairing plasmid-borne resistance. This led to high-level, low-cost antibiotic resistance, but also produced an integrated genome of co-dependent replicons that may limit the onward spread of co-adapted MGEs to other lineages. This evolutionary trajectory was strikingly repeatable across independently evolving populations despite the emergence of multiple competing lineages within populations. The results presented here demonstrate that the interaction between positive selection and compensatory evolution can help to explain the persistence of MDR plasmids in the clinic and the environment.
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Udo, Edet Ekpenyong. "Characterisation and molecular studies of plasmids from Nigerian staphylococci." Curtin University of Technology, School of Biomedical Sciences, 1991. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=15648.
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Fifty three Staphylococcus aureus isolates were obtained from three centres, two hospitals and a private pathology laboratory, and studied for susceptibility to bacteriophages, resistance to antimicrobial agents and plasmid contents.Results of bacteriophage typing revealed that they belonged to a variety of phage types. Eighteen were untypable by any of the International Set of Phages, 16 belonged to phage group 111, nine to group I, four to group 11, two to group IV and two to the miscellaneous group.The isolates were resistant to one or more of methicillin (Mc), benzyl penicillin (Pc), gentamicin (Gm) , kanamycin (Km) , neomycin (Nm) , streptomycin (Sm) , trimethoprim (Tp), sulphonamides (Su), tetracycline (Tc), minocycline (Mn), chloramphenicol (Cm), novobiocin (Nb) and fusidic acid (Fa). Resistance to Pc was due to the production of beta-lactamase (Bla). No resistance to vancomycin, spectinomycin and erythromycin was detected. Resistance was also found to heavy metals such as cadmium (Cd), mercury (Hg), phenyl mercuric acetate (Pma), arsenate (Asa) and to the nucleic-acid binding compounds propamidine isethionate (Pi) and ethidium bromide (Eb).All but one of the isolates harboured plasmids. The number of plasmids the isolates carried varied from one to six and their sizes ranged from < 1.0 kb to c.48 kb.Location of the resistance determinants was ascertained by curing and transfer experiments. Loss of resistance was tested after growth at 43.5°C and transfer of resistance determinants was attempted by transduction, mixed-culture transfer and conjugation. The results revealed that resistance to Mc, Gm, Tp, Mn and Fa was chromosomal in all the resistant isolates and in some isolates Bla and resistance to Sm and Cd were chromosomal as well as plasmid encoded. In the majority of cases Bla and resistance to Km, Nm, Sm, Tc, Cin, Cd, Hg, Asa, Pma, Pi and Eb was encoded ++by plasmids.Conjugation experiments led to the isolation of three unique conjugative plasmids which have not been found to confer resistance to antimicrobials or to produce haemolysins or diffusible pigment (Dip). The three plasmids, pWBG620, pWBG637 and pWBG661, were indistinguishable by restriction endonuclease analysis and DNA-DNA hybridisation. However pWBG620, unlike pWBG637 and pWBG661, was not detected in the cytoplasm of its host and was only detected in transconjugants after it mobilised a non-conjugative Sm-resistance (SmR) plasmid. Further analysis indicated that it is integrated into the chromosome of its host, excises during conjugation and mobilises the SmR plasmid.These plasmids were studied further using pWBG637 as a representative. It was compared with representatives of the two groups of conjugative plasmids which have been reported in the staphylococci. These are the plasmids which encode resistance to Gm, Km and Nm and those which code for the production of diffusible pigment. The three types of conjugative plasmids were compared by restriction endonuclease analysis and DNA- DNA hybridisation and were found to be different. A preliminary restriction map of pWBG637 has also been constructed.However since pWBG637 has no resistance phenotype direct selection for it was not possible in transfer experiments and for incompatibility (Inc.). To study it further it was necessary to construct resistant derivatives which could be selected for in transfer experiments. This was achieved by labelling pWBG637 with resistance transposons to generate two conjugative plasmids, pWBG636 carrying an insert of Tn3851 (Gm- resistance) and pWBG642 carrying an insert of Tn551 (hn- resistance). It was found that transposon labelling had not changed the incompatibility of pWBG637 and therefore pWBG636 and pWBG642 were used in further experiments in place of pWBG637. Inc. ++
tests with the pWBG637 derivatives revealed that the pWBG637 type of plasmid is not only different from the other two types of conjugative plasmids but is different from any of the described staphylococcal Inc. groups and therefore the pWBG637 type of plasmids represent a new Inc. group 15. The pWBG637 type of plasmids were studied further using plasmids pWBG636 and pWBG642. They were able to transfer conjugatively to a capsulated S.aureus strain either by the polyethylene glycol method or on filter membranes. They also transferred by conjugation to S. epidermidis and Streptococcus faecalis and were able to transfer back from these strains to S.aureus indicating that they also replicate in these hosts. Consequently they have been used to mobilise non-conjugative plasmids from S.epidermidis and non phage typable S.aureus. Both plasmids failed to transfer conjugatively to Bacillus subtilis and Escherichia coli.pWBG637 transferred non-conjugative plasmids by mobilising them in a manner similar to mobilisation (donation) in E.coli or by recombining with them to form new resistance plasmids. In one case, pWBG628 which encodes Bla and resistance to Cd, Km, Nm and Sm and has no homology with pWBG637 recombined with it during conjugation to produce three new conjugative plasmids pWBG629, pWBG630 and pWBG631 carrying resistance determinants from pWBG628. One of these plasmids, pWBG629, was found to be pWBG637 which had acquired a 4.5 kb element encoding resistance to Km, Nm and Sm. This element was shown to be transposable in both rec+ and rec- backgrounds and has been designated Tn3854. It expressed Sm resistance in E.coli and differs on this account from the Gram-negative transposon Tn5 which expresses resistance to Km, Nm and Sm in non-enteric bacteria but only resistance to Km and Nm in E. coli.Where possible the non-conjugative plasmids encoding resistance to ++
antimicrobial agents were compared with phenotypically similar plasmids isolated from other parts of the world. It was found that the Tc and Sm resistance plasmids were closely related to other plasmids with the same phenotype whereas the Cm resistance plasmids were different.Although the majority of the Bla plasmids belonged to Inc. group 1 they demonstrated significant restriction enzyme fragment length polymorphism when compared with other Bla plasmids.This study has provided the first data on the genetics of antimicrobial resistance in Nigerian S.aureus. Although many of the plasmids studied were found to be similar to those previously described the isolates also contained some unique and previously undescribed plasmids.
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Coons, Terry M. "Restriction mapping and expression of recombinant plasmids containing the arsenic resistance genes of the plasmid R45." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/3597.
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The trivalent (arsenite) and pentavalent (arsenate) forms of arsenic are introduced into the environment through the use of arsenic in herbicides, pesticides, fertilizers, and the smelting of arsenic-bearing ores. Bacteria resistant to arsenic are readily isolated from surface waters, sewage, and clinical infections. Although some bacterial resistance is provided by inducible phosphate transport systems that discriminate against arsenate, marked resistance is carried on bacterial plasmids.
A 6.9 kilobase fragment previously derived from one such plasmid, R45, and containing the genes for inducible resistance to arsenite and arsenate was ligated into the cloning vectors puce and pUC9 in opposite orientations and transformed into Escherichia coli JM 105. Insertion into the multiple cloning site of the pUC vectors places the inserted fragment under the inducible control of the lac operon promoter. An attempt was made to determine the direction of transcription in the fragment by growth in 10-3 M isopropyl-β-D-thiogalactoside prior to challenge with arsenite.
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Tavakoli, Norma Parvin. "Characterisation of the plasmid pUB2380 and in particular its transposition system." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386071.
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Evans, Jane E. "The conjugation system of Staphylococcus aureus." Thesis, University of Oxford, 1986. https://ora.ox.ac.uk/objects/uuid:1c1f5c11-f854-4af5-b9cf-34fdf279fb28.
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A conjugation system in Staphylococcus aureus has been investigated and shown to be determined, at least in part, by genes carried on plasmids. Conjugation required cell-to-cell contact but not calcium ions. The frequency of conjugation depended on the recipient used and on the incubation conditions. Two conjugative plasmids were mapped by restriction enzyme analysis but experiments to clone the conjugation-determining region were unsuccessful although separate regions specifying gentamicin resistance, ethidium bromide resistance and cadmium resistance were cloned. The gentamicin resistance determinant was probably part of Tn4001. Deletion of various sized pieces of DNA from one of the plasmids resulted in reduction of its ability to specify conjugation but no specific part of this plasmid could be implicated in the process. Further experiments led to the conclusion that this particular plasmid (p8325-4) is probably not self-transmissible but transferred by a phage-mediated system. Strains of Staphylococcus aureus produced a pheromone-like substance that elicited a clumping response in Streptococcus faecalis but no evidence was found for the involvement of staphylococcal conjugative plasmids in this. The conjugative plasmid, p8325-2, mobilized a small plasmid (pT181) but not a chromosomal gene. Insertion of transposon Tn551 was used to produce mutants of the conjugative plasmid p8325-2. Some twenty-six mutants were studied and the position of Tn551 in them mapped. There were preferred regions of insertion for Tn551 and twenty out of the twenty-six mutants had altered ability to conjugate. One showed a significantly higher frequency of conjugation and the other nineteen, all with substantially lower frequencies of conjugation, were mapped to two well-separated regions of the plasmid. Similarity between the locations of these putative regions and those reported for some other conjugative plasmids from staphylococci is striking and suggests a common origin.
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Eldek, Ahmed. "Antibiotic-Regulated Plasmid Copy Number Variation: A Driver of Antibiotic Resistance?" Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388523.
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Plasmids are small circular DNA molecules within bacterial cells that are separated from the bacterial chromosome and replicate independently. Also, they play a crucial role in the dissemination of antibiotic resistance genes among bacteria through horizontal gene transfer. They can be present in many copies within host cell, which is known as plasmid copy number. Plasmids can regulate their own copy number by different mechanisms. Additionally, the selective pressure can also play a pivotal role in determining plasmid copy number. The presence of antibiotics in the surrounding environment can drive variations of plasmid copy number. In this study, we examined plasmid copy number variations of multidrug resistance plasmids in presence of antibiotics by using EvaGreen® - based multiplexed digital droplet PCR. We could observe that cultures of Klebsiella pneumoniae and Escherichia coli harboring multidrug resistance plasmids grown in presence of sub-MIC concentrations of the antibiotics did not show high variations in plasmid copy numbers. On the other hand, mutants of K. pneumoniae selected for increased antibiotic resistance showed high increases in copy number of a multidrug-resistance plasmid.
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Khan, Azra. "An investigation into the association of plasmid-borne qacAB and antimicrobial resistance in meticillin-resistant Staphylococcus aureus." Thesis, University of Portsmouth, 2013. https://researchportal.port.ac.uk/portal/en/theses/an-investigation-into-the-association-of-plasmidborne-qacab-and-antimicrobial-resistance-in-meticillinresistant-staphylococcus-aureus(49b2b0fc-936a-412a-b418-8d9d24d3b531).html.
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Meticillin-resistant Staphylococcus aureus (MRSA) is globally recognised as a major causative organism of hospital acquired infection (HAI) and continues to present many challenges for infection prevention and control. Once established within hospitals and healthcare centers, the control of spread of MRSA and therapy is difficult due to resistance to otherwise effective antimicrobials. Government initiatives in the United Kingdom (UK) have led to considerable investments in improving infection control practices, with emphasis on improving hand hygiene compliance of healthcare professionals and hospital environmental cleanliness to control the spread and limit the source of MRSA and other HAIs. This has resulted in the subsequent increase in disinfectant and antiseptic usage containing, quaternary ammonium compounds (QACs), cationic biocides such as chlorhexidine and the bisphenol ether, triclosan, for decontamination of surfaces and disinfection of skin. Thus, there is serious concern that as with antibiotic resistance, continual and intensive exposure of MRSA (and other hospital pathogens) to biocides, may result in the emergence of resistance to these agents with further detrimental consequences and substantial burden for prevention, treatment and control of hospital infections. MRSA carry a number of plasmid-borne qac genes, predominantly qacA, qacB and smr that encode resistance to commonly used antiseptics and disinfectants in hospitals, nursing homes and other healthcare establishments. The proteins encoded by qacA and qacB mediate efflux via active transport; QacA multidrug exporter mediates resistance to monovalent, divalent cationic and lipophilic antimicrobial compounds, whilst the closely related export protein QacB mediates lower levels of resistance to divalent cations. In this research a “snapshot” study of hospital strains of MRSA stored at the Hospital Infection Research Laboratory (HIRL), City Hospital, Birmingham, was carried out to determine the prevalence and distribution of qacAB in these isolates and determine a possible association between presence of these genes and biocide resistance. The intercalating dye, ethidium bromide (EtBr) is a substrate for many S. aureus multi-drug resistant (MDR) efflux pumps and was used in the present study as a marker for detection of efflux pump activity. Previous studies have reported that MRSA strains with an MIC of ≥ 64 mg/L to EtBr have qacAB, however, the present study used a lower baseline value of ≥ 32 mg/L resistance to EtBr to capture any isolates with low MICs that may have qacAB and may be missed. Initially 3,400 MRSA strains collected between October 2002 and October 2006 were screened to identify and select isolates with ≥ 32 mg/L resistance to EtBr. A second MRSA collection stored at the Antimicrobial Chemotherapy Laboratory, City Hospital, Birmingham, comprised 63 isolates that showed MICs of ≥ 64mg/L, were also included in the study. At this stage the study set (Set A) comprised 112 isolates with varying MIC to EtBr ranging from ≥ 32 mg/L to 256 mg/L. At a later date an additional 400 strains were screened from the same stored collection to include strains with lower MICs, i.e. < 32 mg/L. Thus a total of 336 isolates with varying levels of resistance to EtBr were studied. PCR was carried out on all 336 isolates for detection o qacAB, smr, qacG, qacH and qacJ to determine the presence and prevalence of the genes. Set A isolates positive for qacAB were further investigated to differentiate between qacA and qacB. Restriction digestion using the restriction enzyme Rsa1 was carried out on PCR products followed by PCR using specific primers for detection of the two genes. Urease activity and neomycin sensitivity were used as a means of basic characterization applied to all the study isolates. A select number of samples negative for qacA and qacB were typed using spa typing. Transfer studies involving, conjugation, plate mating and transformation on selected strains were carried out to attempt transfer of qacAB using the marker EtBr from a strain of MRSA with an MIC of ≥ 256 mg/L to EtBr and qacAB positive to a strain with < 32mg/L MIC to EtBr and lacking qacAB. Unfortunately, conjugation experiments were not successful in this study. Plasmid curing experiments were also carried out to demonstrate loss of plasmid through continual passaging onto selective plates. A variety of antiseptics and disinfectants are used in hospitals for prevention of HAIs. The present study was limited to carrying out minimum bactericidal concentration (MBC) determinations and MIC of four commonly used hospital biocides against randomly selected strains. The strains reflected ranges of MICs to EtBr and presence or absence of qacAB. These experiments, determined the efficacy of the biocides tested, to effectively destroy MRSA on skin and environment when used in healthcare settings. The results suggest that in the majority of strains showing high MICs to EtBr i.e. ≥ 64 mg/L, qacAB is present and thus, the mechanism of resistance to biocides may be attributed to an efflux protein pump encoded by these genes. Following restriction digestion of qacAB positive strains, with the restriction enzyme Rsa1, 81 of the 112 qacAB positive strains tested positive for qacA, i.e. 90% and 9 (11%) for qacB. The predominant prevalence of the qacA gene indicates that most of these strains are likely to be resistant to organic cationic biocides and intercalating dyes such as EtBr and acriflavine. However, the results of the MIC and MBC determinations carried out on a selection of biocides commonly used in the healthcare environment implies that the four biocides tested are likely to be 99.9% effective at killing the majority of isolates in this study set. However, five isolates demonstrated MBCs to chlorhexidine of > 32 mg/L. Chlorhexidine is a compound that is widely used in hand hygiene and surgical antisepsis products, and the results suggest that solutions containing this compound would be ineffective in removing MRSA from the hands of healthcare workers and skin sites if used. Molecular spa typing of selected samples negative for qacAB revealed that Endemic-MRSA (EMRSA) type 15 was the most frequent spa type identified in this study, followed by EMRSA-16 and EMRSA-1. Three strains identified jointly as EMRSA-3 and EMRSA-1. One strain identified as the Berlin clone. With regards to the challenges presented to infection prevention and control, MRSA has the potential to develop increased tolerance to biocides commonly used in the hospital environment, due to expression of efflux pumps, although currently there is little evidence of this. Further research is required to understand and learn of the various mechanisms of resistance, supported by adherence to control of infection strategies for prevention and spread of infections in healthcare facilities.
Books on the topic "Plasmid resistance"
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Barrett, Siobhán. Studies on plasmid-mediated copper resistance in Escherichia coli. Birmingham: Universityof Birmingham, 1994.
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Laroussi, M. Plasma medicine: Applications of low-temperature gas plasmas in medicine and biology. Cambridge: Cambridge University Press, 2012.
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Foley, Ian Michael. Population dynamics in enterococcal biofilms: Resistance plasmids and antibiotic susceptibility. Manchester: University of Manchester, 1996.
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W, Adams Matthew, White D. F, and Risk Reduction Engineering Laboratory (U.S.), eds. Evaluation of the chemical resistance of geotextiles, geonet, and pipe. Cincinnati, Ohio: Risk Reduction Engineering Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 1992.
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Goel, Subhash C. Performance-based plastic design: Earthquake-resistant steel structures. Country Club Hills, IL: International Code Council, 2008.
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Goel, Subhash C. Performance-based plastic design: Earthquake-resistant steel structures. Country Club Hills, IL: International Code Council, 2008.
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Goel, Subhash C. Performance-based plastic design: Earthquake-resistant steel structures. Country Club Hills, IL: International Code Council, 2008.
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Goel, Subhash C. Performance-based plastic design: Earthquake-resistant steel structures. Country Club Hills, IL: International Code Council, 2008.
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Mallinson, John H. Corrosion-resistant plastic composites in chemical plant design. New York: M. Dekker, 1988.
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Shih-Ho, Chao, and National Council of Structural Engineers Associations., eds. Performance-based plastic design: Earthquake-resistant steel structures. Country Club Hills, IL: International Code Council, 2008.
Find full textBook chapters on the topic "Plasmid resistance"
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Taylor, Diane E., Amera Gibreel, Trevor D. Lawley, and Dobryan M. Tracz. "Antibiotic Resistance Plasmids." In Plasmid Biology, 473–91. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555817732.ch23.
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Gooch, Jan W. "Resistance (R) Plasmid." In Encyclopedic Dictionary of Polymers, 920. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_14681.
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Jacoby, George A., Jacob Strahilevitz, and David C. Hooper. "Plasmid-Mediated Quinolone Resistance." In Plasmids, 475–503. Washington, DC, USA: ASM Press, 2015. http://dx.doi.org/10.1128/9781555818982.ch25.
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Jacoby, George A. "Plasmid-Mediated Quinolone Resistance." In Antimicrobial Drug Resistance, 207–10. Totowa, NJ: Humana Press, 2009. http://dx.doi.org/10.1007/978-1-59745-180-2_17.
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Jacoby, George A. "Plasmid-Mediated Quinolone Resistance." In Antimicrobial Drug Resistance, 265–68. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-46718-4_17.
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Litake, Geetanjali M. "Plant-Assisted Plasmid Curing Strategies for Reversal of Antibiotic Resistance." In Antimicrobial Resistance, 559–75. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-3120-7_18.
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Kelly, Michael D., and Joel E. Mortensen. "A Low-Copy Number Plasmid Mediating β-Lactamase Production by Xanthomonas Maltophilia." In Antimicrobial Resistance, 71–80. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4757-9203-4_6.
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Schwarz, Stefan, Jianzhong Shen, Sarah Wendlandt, Andrea T. Feßler, Yang Wang, Kristina Kadlec, and Cong-Ming Wu. "Plasmid-Mediated Antimicrobial Resistance in Staphylococci and Other Firmicutes." In Plasmids, 421–44. Washington, DC, USA: ASM Press, 2015. http://dx.doi.org/10.1128/9781555818982.ch22.
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Cullen, D. W., I. M. Packer, and D. J. Platt. "Plasmid Mediated Resistance to Hexavalent Chromium in Agrobacterium." In The Release of Genetically Modified Microorganisms—REGEM 2, 237–40. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4613-0493-7_47.
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Jacoby, George A. "Study of Plasmid-Mediated Quinolone Resistance in Bacteria." In Methods in Molecular Biology, 317–25. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-7459-7_22.
Full textConference papers on the topic "Plasmid resistance"
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Omer, Lawin, Zirak Abdulrahman, and Rastee Saeed. "Curing analysis of Drug Resistance Plasmid in Proteus mirabilis." In 4th International Scientific Conference of Cihan University-Erbil on Biological Sciences. Cihan University-Erbil, 2017. http://dx.doi.org/10.24086/bios17.05.
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Dheyab, Ali. "Cloning Antibiotic Resistance Plasmid of Staph .aureus Isolated From Clinical Sample." In المؤتمر العلمي الدولي التاسع - "الاتجاهات المعاصرة في العلوم الاجتماعية، الانسانية، والطبيعية". شبكة المؤتمرات العربية, 2018. http://dx.doi.org/10.24897/acn.64.68.145.
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Liao, Pinyu. "Exploiting Plasmid-Mediated Resistance: Design of Small-Molecule Inhibitors for the Disruption of the Kid-Kis Toxin-Antitoxin System in Plasmid R1." In 2022 IEEE 12th International Conference Nanomaterials: Applications & Properties (NAP). IEEE, 2022. http://dx.doi.org/10.1109/nap55339.2022.9934272.
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Sauer, S., U. Pudich, B. Bernd Gericke, Rita Prager, A. Fruth, E. Brockhaus, H. Tschäpe, and W. Rabsch. "An outbreak caused by S. Typhimurium DT177, BTa in Bavaria characterized by an unusual antibiotic resistance and plasmid profile." In Fourth International Symposium on the Epidemiology and Control of Salmonella and Other Food Borne Pathogens in Pork. Iowa State University, Digital Press, 2001. http://dx.doi.org/10.31274/safepork-180809-1136.
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Shams, Noora, Hanin AlHiraky, Nabila Moulana, Maissa Riahihi, Kaltham Alsowaidi, Khawlah Albukhati, Susu Zughair, and Nahla Eltai. "Comparison of Available Methods for Investigating The in vitro Activity of Colistin Against Different Gram-Negative Bacilli." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2021. http://dx.doi.org/10.29117/quarfe.2021.0121.
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Background: The surge in the prevalence of multidrug-resistant (MDR) Gram-negative bacterial infections with limited treatment options and the decrease in the development of new antibiotics are challenges that lead to the reuse of colistin to treat infections caused by MDR pathogens. This study aimed to determine economical, simple, and reliable colistin susceptibility testing methods as an alternative to the time and effort-consuming microdilution technique and identify the colistin resistance's genetic determinants to find if it affects the testing method. Material and Methods: Seven colistin susceptibility testing methods, namely, Disk diffusion, E-test, ComASPTM SensiTest, broth disk elution, colistin agar test, CHROMagarTM COL-APSE, and BD Phoenix ID/AST, were compared to the gold standard broth microdilution. Data of the 63 studied isolates were analyzed using very major error (VME), major error (ME), categorical agreement (CA), sensitivity, specificity, Kappa, positive and negative predictive values. Whole-genome sequencing was performed on all isolates to determine if the genetic resistant factors affect the accuracy of the specific colistin susceptibility testing method. Results: Our results revealed that disk diffusion is still an ineffective method for measuring colistin susceptibility with the highest ME (31.75%), the lowest Kappa 0 (0%), and CA (68.25%) values. In contrast, the highest sensitivity, specificity, CA, kappa value, positive and negative predictive values were reported on Phoenix, ComASPTM sensitest, and E-test methods compared with the microbroth dilution reference method. Our study did not ensure any relation between the type of colistin resistance genetic determinant (chromosomal/plasmid-mediated) and the performance of the specific colistin susceptibility test Conclusions: Phoenix, E-test, and CompASPT SensiTest methods have remained superior in reproducibility, sturdiness, simplicity of use with a performance similar to the current recommended BMD procedure. These methods can be an alternative to the current laborious, impractical broth microdilution technique, especially in microbiology laboratories with a large workload.
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BAQER, Batool Abd Al Ameer, and Maysoon Khaleefah ABBAS. "EFFECT OF CEPHALOSPORINS ON ( BIOFILM PRODUCTION AND PROTEASE ) ACTIVITIES BY SOME BACTERIA ISOLATED FROM OTITIS MEDIA." In III.International Scientific Congress of Pure,Appliedand Technological Sciences. Rimar Academy, 2021. http://dx.doi.org/10.47832/minarcongress3-1.
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30 samples (swab) were collected from patients suffering from Otitis media. Swabs were implanted on the culture media blood agar and MacConkey agar to isolate the bacteria and to diagnose them using microscopic, culture and biochemical tests and confirmed by the Vitck-2 system. Of the total, 18 isolates were selected which belong to 8 (26.6%) Staphylococcus aureus, 5 (16.6%) Klebsiella pneumonia, and 4 (13.3%) Escherichia coli. All isolates were investigated for sensitivity to (18) antibiotics, six of them from the cephalosporins group The results showed that all isolates were 100% resistance to Cefotaxime, Ceftazidime, Cefixime, Ceftriaxone, Cefepime, Cefoxitin, Aztronam, Ampenicillin, while the isolates showed the lowest percentage of resistance to Imipenem (4.54) %, while all differences showed a clear difference in some of their resistance. Of the antagonists (Vancomycin, Erythromycin, Rifampin) with a percentage of (95.45, 27.27, 18.18)%, respectively. but for concentrations (4–16)µg/ml were ineffective for some of them. The (Minimal inhibitory concentrations ) MIC test indicated that it ranged between (4–32)µg/ml for Ceftriaxone and (16–32)µg/ml for Ceftazidime. All isolates were shown ability have (100%) activity to produce (Biofilm) was tested on the Congo red agar (CRA) medium, and ability to produce a protease enzyme by (72.22%) on Skim milk agar medium. The results showed a effect of inhibitory concentrations of Ceftriaxone on the activity of biofilm production and the protease enzyme, further the results of this study showed that the following concentrations (1024, 512, 256 and 128)µg/ml were lethal to isolates, while (32–64)µg/ml were inhibitory, Also, the molecular diagnosis shown results of Agarose - gel electrophoresis of both (normal case) S. aureus, E. coli and Kl. pneumonia and heal isolates observed the presence of chromosomal and plasmid DNA bands in the normal status but alone chromosomal DNA bands occur with the isolates deal in Ceftriaxone at levels of (32–128 )µg/ml. In the study of the effect of some Gram-negative bacteria by using IL-2 human. It can be used in the diagnosis of inflammation of the Otitis Media. Key words: Cephalosporins, Otitis media, Biofilm, protease, E. coli, Staphylococcus aureus, Klebsiella pneumonia.
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Vargas, F., H. Ageorges, P. Fauchais, and M. E. Lopez. "Evaluation of the Elastic and Plastic Contact Wear Performance of Plasma and Flame Sprayed 13 and 45 wt% TiO2 Alumina-Titania Coatings." In ITSC2011, edited by B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and A. McDonald. DVS Media GmbH, 2011. http://dx.doi.org/10.31399/asm.cp.itsc2011p1445.
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Abstract Atmospheric plasma and oxy-acetylene flame were used to spray alumina-titania micrometer sized particles with respectively 13 wt.% and 45 wt.% of TiO2 (AT-13 and AT-45). Plasma spraying was also used to spray nanometer-sized- agglomerated particles (AT-13). The enthalpy of spray guns was varied to achieve coatings with different phases and structural characteristics. The influence of the different structural characteristics and the phases of coatings on their hardness and tribological behavior was then studied. The wear resistance was determined by dry elastic contact between an alumina ball, 6 mm in diameter, and the polished coated discs. The ball was moved at a linear speed of 0.1 m/s under a load of 5 N during 20,000 cycles. Drilling tests between a steel drill bit, 12.5 mm in diameter, and the coating surface were also carried out in order to determine the wear resistance under plastic contact. The wear test results showed that AT-13 coatings were more resistant than the AT-45 ones, which was due to the presence of α and γ alumina, phases presenting a high mechanical resistance. On the contrary the resistance of AT-45 coatings, consisting of Al2TiO5 and Al6Ti2O13 brittle phases of low hardness, was poorer. Under elastic contact the reduction of the wear resistance of coatings elaborated by flame spraying was not obvious, but under plastic contact the plasma sprayed coatings were more resistant than those deposited by oxy-acetylene flame.
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Ding, Z., R. Knight, and R. W. Smith. "Abrasive Wear Characteristics of Ni-base Self-fluxing Alloy Spraywelding Overlays." In ITSC 1997, edited by C. C. Berndt. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.itsc1997p0091.
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Abstract The results of low stress, pin-on-disc and high stress grinding abrasive wear tests on coatings produced by plasma and oxy-acetylene flame spraywelding are presented. FNil5A and FNiWC35 Ni-based self-fluxing alloys were selected as typical spraywelding materials for abrasive wear resistance. The abrasive wear resistance mechanisms of welded overlays produced by various materials and processes were also characterized by hardness tests, microstructural and compositional analyses, and through analysis of the effect of different kinds of abrasive on the wear resistant of Ni-base self-fluxing spraywelding overlays. Results showed that FNiWC35 overlays exhibited improved resistance under low stress abrasion, but the relative wear resistances of FNiWC35 and FNil5A still depended primarily on the type and hardness of the abrasive medium used. For the same material, the abrasive wear resistance of oxyacetylene flame sprayed overlays was higher than that produced by plasma spraywelding. The wear resistance of the plasma spraywelding overlays depended not only on the material, but also strongly on the spraywelding process parameters.
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Takahashi, S., M. Hatano, Y. Kojima, Y. Harada, A. Kawasaki, and F. Ono. "Thermal Cycle Resistance of Oxidation-Resistant Metallic Coatings." In ITSC2010, edited by B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. DVS Media GmbH, 2010. http://dx.doi.org/10.31399/asm.cp.itsc2010p0695.
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Abstract Thermal cycle resistance of Ni-20Cr, Ni-50Cr and CoNiCrAlY coatings manufactured by air plasma spraying was investigated according to a Japanese Industrial Standard "Testing method for thermal cycle resistance of oxidation resistant metallic coatings (JIS H 8452)” established in 2008. The specimens were exposed at 1000 °C and 1093 °C in air under cyclic heating and cooling condition up to 100 times. The thermal cycle resistance of oxidation-resistant metallic coatings was found to depend strongly on the testing temperature and the chemical composition of the coating materials. In the thermal cycle test at 1000 °C, the remarkable failure was not observed in any specimen. However, in the thermal cycle test at 1093 °C, although the Ni-20Cr coating caused the spalling on the whole surface of coating, the Ni-50Cr and the CoNiCrAlY coatings exhibited the excellent thermal cycle resistance even after applying the thermal cycles of 100 times, The CoNiCrAlY coating showed the mass gain with increasing the numbers of thermal cycle due to the preferential oxidation between the splats of the thermal spray particles. Furthermore, the failure behavior of specimens was investigated in detail by SEM, XRD and EPMA etc.
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Muntyan, Victoria S., Alla S. Saksaganskaia, Alexey N. Muntyan, Mariia E. Vladimirova, and Marina L. Roumiantseva. "STRESS AND IMMUNITY OF NODULE BACTERIA SINORHIZOBIUM MELILOTI: LOCALIZATION, POLYMORPHISM AND PHYLOGENY OF GENETIC DETERMINANTS." In 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022/6.1/s25.15.
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Sinorhizobium meliloti are agriculturally valuable species of soil bacteria that form nitrogen-fixing symbiosis with alfalfa plants. Global climate changes lead to an increase of agricultural areas subjected to salinity. Current knowledge about about high-salt stress impact on soil saprophitic root nodulated microsymbionts of legumes is weakly studied and rhizobia gene pool responsible for salt tolerance are fragment and far from clear. An increase of bacteria nonspecific resistance (immune status) to unfavorable stress factors can occur through the induction of defense mechanisms like restrictionmodification systems and CRISPR/cas systems which are aimed to protect bacteria cells from bacteriophages widespread in soil microbiome. The aim of this research was to evaluate the role of the megaplasmid pSymA in the formation of ecological genome of S. meliloti, which is related to stress tolerance and to determine the location of elements of adaptive immune systems protecting root nodule bacteria against external foreign DNA. The analysis was done on 11 genes, products of which involved in response to ion stress and synthesis of osmoprotectors. It was found that 6 out of 11 genes were found in the genomes of all analyzed S. meliloti strains, while it was not a case for other 5 genes. It was found that, unlike chromosome, megaplasmid I of S. meliloti accumulated copies of 4 from 5 genes, except kdpA gene, which is represented by a single copy and localized on megaplasmid I in all so far studied strains. It was predicted that closest phylogenetic relatives of genes whose products are involved in response to ion stress as well in synthesis of osmoprotectors are homologous genes of closely related S. medicae species. The exception was for betI2, for which the closest phylogenetic relative was homologous gene of Klebsiella pneumonia, and another exception is kdpA gene introduced onto megaplasmid-I from actinobacteria. Regarding elements of immune systems it was revealed that nonsymbiotic plasmids of S. meliloti harbored incomplete elements of RMS-I, -II, and - III systems, while the 4 complete RMS-IV systems were detected on a single plasmid. It was found out that corresponding methylases had similarities with similar enzymes detected in nitrogen-fixing strains of Agrobacterium tumefaciens, Mezorhizobium sp., Bradyrhizobium sp. CRISPR sequences were not detected on megaplasmid-I, while they were on chromosome, megaplasmid-II and on cryptic plasmids. So, it was concluded that megaplasmid-I of S. meliloti are enriched in copies of genes related to osmotic stress tolerance, but it role in immune status of rhizobia is requested further elucidation.
Reports on the topic "Plasmid resistance"
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Trezona, Thomas. Plasmid-mediated resistance to arsenite and arsenate in Escherichia coli. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.3125.
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Coons, Terry. Restriction mapping and expression of recombinant plasmids containing the arsenic resistance genes of the plasmid R45. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.5481.
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Barefoot, Susan, Benjamin Juven, Thomas Hughes, Avraham Lalazar, A. B. Bodine, Yitzhak Ittah, and Bonita Glatz. Characterization of Bacteriocins Produced by Food Bioprocessing Propionobacteria. United States Department of Agriculture, August 1992. http://dx.doi.org/10.32747/1992.7561061.bard.
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Objectives were to further characterize activity spectra of dairy propionibacteria bacteriocins, jenseniin G and propionicin PLG-1, purify them, examine the role of cell walls in resistance, examine their interactions with cytoplasmic membrane, explain producer immunity, and clone the responsible genes. Inhibitory spectra of both bacteriocins were further characterized. Propionicin was most effective in controlling Gram-positive, rather than Gram-negative organisms; it controlled growth of sensitive cells both in a culture medium and a model food system. Jenseniin inhibited yogurt cultures and may help prevent yogurt over-acidification. Both were active against botulinal spores; jenseniin was sporostatic; propionicin was sporicidal. Jenseniin was produced in broth culture, was stable to pH and temperature extremes, and was purified. Its molecular mass (3649 Da) and partial amino acid composition (74%) were determined. A blocked jenseniin N-terminus prevented sequencing. Methods to produce propionicin in liquid culture were improved, and large scale culture protocols to yield high titers were developed. Methods to detect and quantify propionicin activity were optimized and standardized. Stability of partially purified propionicin was demonstrated and an improved purification scheme was developed. Purified propionicin had a 9328-Da molecular mass, contained 99 amino acids, and was significantly hydrophobic; ten N-terminal amino acids were identified. Propionicin and Jenseniin interacted with cytoplasmic membranes; resistance of insensitive species was cell wall-related. Propionicin and jenseniin acted similarly; their mode of action appeared to differ from nisin. Spontaneous jenseniin-resistant mutants were resistant to propionicin but nisin-sensitive. The basis for producer immunity was not resolved. Although bacteriocin genes were not cloned, a jenseniin producer DNA clone bank and three possible vectors for cloning genes in propionibacteria were constructed. In addition, transposon Tn916 was conjugatively transferred to the propionicin producer from chromosomal and plasmid locations at transfer frequencies high enough to permit use of Tn916 for insertional mutagenesis or targeting genes in propionibacteria. The results provide information about the bacteriocins that further supports their usefulness as adjuncts to increase food safety and/or quality.
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Freeman, Stanley, and Russell J. Rodriguez. The Interaction Between Nonpathogenic Mutants of Colletotrichum and Fusarium, and the Plant Host Defense System. United States Department of Agriculture, September 2000. http://dx.doi.org/10.32747/2000.7573069.bard.
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The intent of this proposal was to study the interaction between nonpathogenic mutants of Colletotrichum magna and Fusarium oxysporum, and the cucurbit host defense system. We had shown previously that a nonpathogenic endophytic mutant path- 1 of C. magna, caused no visible disease symptoms but protected watermelon seedlings from disease caused by the wildtype isolate and F. o. niveum. Objectives were: 1) Determine the microscopic, biochemical and molecular genetic interaction between "protected" (path- 1 colonized) cucurbit hosts and wildtype isolates of C. magna; 2) Isolate non-pathogenic mutants of F.o. melonis and test feasibility for protecting plants against fungal diseases. We found that path-1 caused no visible disease symptoms in cucurbit seedlings but conferred disease resistance against pathogenic isolates of C. magna, C. orbiculare, and F. oxysporum. Disease resistance conferred by path-1 correlated to a decrease in the time of activation of host defense systems after exposure of path-1 colonized plants to virulent pathogens. This was determined by monitoring the biochemical activity of PAL and peroxidase, and the deposition of lignin. It appears that path-1-conferred disease resistance is a multigenic phenomenon which should be more difficult for pathogen to overcome than single gene conferred resistance. Based on the benefits conferred by path-1, we have defined this mutant as expressing a mutualistic lifestyle. REMI (restriction enzyme-mediated integration) nonpathogenic mutants were also isolated using pHA1.3 plasmid linearized with Hind III and transformed into wildtype C. magna. The integrated vector and flanking genomic DNA sequences in REMI mutant R1 was re-isolated and cloned resulting in a product of approximately 11 kb designated pGMR1. Transformations of wildtype C. magna with pGMR1 resulted in the same non-pathogenic phenotype. A nonpathogenic mutant of F.o. melonis (pathogenic to melon) was isolated that colonized melon plants but elicited no disease symptoms in seedlings and conferred 25 - 50% disease protection against the virulent wildtype isolate. Subsequently, nonpathogenic mutant isolates of F.o. niveum (pathogenic to watermelon) were also isolated. Their protection capacity against the respective wildtype parent is currently under investigation. This research has provided information toward a better understanding of host-parasite interactions; specifically, endophytes, pathogens and their hosts. It will also allow us to assess the potential for utilizing nonpathogenic mutants as biological control agents against fungal pathogens and isolating molecular genetic factors of pathogenicity in Fusarium.
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Lindow, Steven E., Shulamit Manulis, Dan Zutra, and Dan Gaash. Evaluation of Strategies and Implementation of Biological Control of Fire Blight. United States Department of Agriculture, July 1993. http://dx.doi.org/10.32747/1993.7568106.bard.
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The main objective of this study was to develop data that would facilitate a consistently effective method of biological control of fire blight disease to be developed and to enable its implementation for disease control by ensuring its compatibility with variations in the biological, environmental, and chemical conditions present in pear orchards. As considerable information on the pathogen and biological control of fire blight was already gathered from studies in California and elsewhere, an emphasis was placed on investigating the genetics and ecology of Erwinia amylovora, the causal agent of fire blight in Israel. Studies of plasmid profile, virulence on several host, serological characteristics, as well as DNA fingerprints with selected primers all revealed E. amylovora strains in Israel to be homogeneous. Strains did vary in their resistance to streptomycin, with those from more northern locations being resistant while those in the southern costal plain were all sensitive to streptomycin. Resistance appeared to be conferred by chromosomal mutations as in streptomycin-resistant strains in California. The biological control agent Pseudomonas fluorescens strain A506 colonized flowers of both the Costia and Spodona pear cultivars in Israel as well as Bartlett pear in California. Flowers that were open at the time of spray inoculation of trees subsequently harbored from 105 to 107 cells of strain A506 per flower, while those that opened subsequent to spraying developed population sizes of about 105 cells/flower within 5 days. The incidence of fire blight infections were reduced about 3-fold in several trials in which moderate amounts of disease occurred in the plot areas; this degree of biological control is similar to that observed in California and elsewhere. On two occasions warm and moist weather that favored disease led to epidemics in which nearly all flowers became infected and which was so severe that neither P. fluorescens strain A506 nor chemical bactericides reduced disease incidence. A novel method for identifying antagonistic microorganisms for biological control of fire blight and other diseases was developed. A bacterial ice nucleation gene was introduced into E. amylovora to confer an Ice+ phenotype and the population sizes of this modified pathogen on flowers that had been pre-treated with potential control agents was estimated by measuring the freezing temperature of colonized flowers. Antagonistic strains that prevented the growth of E. amylovora in flowers were readily detected as those in which flowers froze at a low temperature. The method is both rapid and unbiased and several bacterial strains with substantial biological control potential have been identified using this method.
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Hutchinson, M. L., J. E. L. Corry, and R. H. Madden. A review of the impact of food processing on antimicrobial-resistant bacteria in secondary processed meats and meat products. Food Standards Agency, October 2020. http://dx.doi.org/10.46756/sci.fsa.bxn990.
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For meat and meat products, secondary processes are those that relate to the downstream of the primary chilling of carcasses. Secondary processes include maturation chilling, deboning, portioning, mincing and other operations such as thermal processing (cooking) that create fresh meat, meat preparations and ready-to-eat meat products. This review systematically identified and summarised information relating to antimicrobial resistance (AMR) during the manufacture of secondary processed meatand meat products (SPMMP). Systematic searching of eight literature databases was undertaken and the resultantpapers were appraised for relevance to AMR and SPMMP. Consideration was made that the appraisal scores, undertaken by different reviewers, were consistent. Appraisal reduced the 11,000 initially identified documents to 74, which indicated that literature relating to AMR and SPMMP was not plentiful. A wide range of laboratory methods and breakpoint values (i.e. the concentration of antimicrobial used to assess sensitivity, tolerance or resistance) were used for the isolation of AMR bacteria.The identified papers provided evidence that AMR bacteria could be routinely isolated from SPMMP. There was no evidence that either confirmed or refuted that genetic materials capable of increasing AMR in non-AMR bacteria were present unprotected (i.e. outside of a cell or a capsid) in SPMMP. Statistical analyses were not straightforward because different authors used different laboratory methodologies.However, analyses using antibiotic organised into broadly-related groups indicated that Enterobacteriaceaeresistant to third generation cephalosporins might be an area of upcoming concern in SPMMP. The effective treatment of patients infected with Enterobacteriaceaeresistant to cephalosporins are a known clinical issue. No AMR associations with geography were observed and most of the publications identified tended to be from Europe and the far east.AMR Listeria monocytogenes and lactic acid bacteria could be tolerant to cleaning and disinfection in secondary processing environments. The basis of the tolerance could be genetic (e.g. efflux pumps) or environmental (e.g. biofilm growth). Persistent, plant resident, AMR L. monocytogenes were shown by one study to be the source of final product contamination. 4 AMR genes can be present in bacterial cultures used for the manufacture of fermented SPMMP. Furthermore, there was broad evidence that AMR loci could be transferred during meat fermentation, with refrigeration temperatures curtailing transfer rates. Given the potential for AMR transfer, it may be prudent to advise food business operators (FBOs) to use fermentation starter cultures that are AMR-free or not contained within easily mobilisable genetic elements. Thermal processing was seen to be the only secondary processing stage that served as a critical control point for numbers of AMR bacteria. There were significant linkages between some AMR genes in Salmonella. Quaternary ammonium compound (QAC) resistance genes were associated with copper, tetracycline and sulphonamide resistance by virtue of co-location on the same plasmid. No evidence was found that either supported or refuted that there was any association between AMR genes and genes that encoded an altered stress response or enhanced the survival of AMR bacteria exposed to harmful environmental conditions.
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Top, Eva M., and Ben Ridenhour. Persistence of Antibiotic Resistance Plasmids in Biofilms. Fort Belvoir, VA: Defense Technical Information Center, October 2014. http://dx.doi.org/10.21236/ada614277.
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Top, Eva M., and Silvia E. Smith. Persistence of Antibiotic Resistance Plasmids in Biofilms. Fort Belvoir, VA: Defense Technical Information Center, October 2013. http://dx.doi.org/10.21236/ada615372.
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Saadeh, Shadi, and Pritam Katawał. Performance Testing of Hot Mix Asphalt Modified with Recycled Waste Plastic. Mineta Transportation Institute, July 2021. http://dx.doi.org/10.31979/mti.2021.2045.
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Plastic pollution has become one of the major concerns in the world. Plastic waste is not biodegradable, which makes it difficult to manage waste plastic pollution. Recycling and reusing waste plastic is an effective way to manage plastic pollution. Because of the huge quantity of waste plastic released into the world, industries requiring a large amount of material, like the pavement industry, can reuse some of this mammoth volume of waste plastics. Similarly, the use of reclaimed asphalt pavement (RAP) has also become common practice to ensure sustainability. The use of recycled waste plastics and RAP in HMA mix can save material costs and conserve many pavement industries’ resources. To successfully modify HMA with RAP and waste plastic, the modified HMA should exhibit similar or better performance compared to conventional HMA. In this study, recycled waste plastic, linear low-density polyethylene (LLDPE), and RAP were added to conventional HMA, separately and together. The mechanical properties of conventional and modified HMA were examined and compared. The fatigue cracking resistance was measured with the IDEAL Cracking (IDEAL CT) test, and the Hamburg Wheel Tracking (HWT) test was conducted to investigate the rutting resistance of compacted HMA samples. The IDEAL CT test results showed that the cracking resistance was similar across plastic modified HMA and conventional HMA containing virgin aggregates. However, when 20% RAP aggregates were used in the HMA mix, the fatigue cracking resistance was found to be significantly lower in plastic modified HMA compared to conventional HMA. The rutting resistance from the HWT test at 20,000 passes was found to be similar in all conventional and modified HMA.
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Almoumen, Rawan. Undrained Cyclic Shear Resistance of Low Plastic Silts. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.7512.
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