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Published: 4 June 2021
Last updated: 20 February 2023

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1

Matsumoto, Yoshimi, and Matsuhisa Inoue. "Characterization of SFO-1, a Plasmid-Mediated Inducible Class A β-Lactamase from Enterobacter cloacae." Antimicrobial Agents and Chemotherapy 43, no. 2 (February 1, 1999): 307–13. http://dx.doi.org/10.1128/aac.43.2.307.

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ABSTRACT Enterobacter cloacae 8009 produced an inducible class A β-lactamase which hydrolyzed cefotaxime efficiently. It also hydrolyzed other β-lactams except cephamycins and carbapenems. The activity was inhibited by clavulanic acid and imipenem. Thebla gene was transferable to Escherichia coliby electroporation of plasmid DNA. The molecular mass of the β-lactamase was 29 kDa and its pI was 7.3. All of these phenotypic characteristics of the enzyme except for inducible production resemble those of some extended-spectrum class A β-lactamases like FEC-1. The gene encoding this β-lactamase was cloned and sequenced. The deduced amino acid sequence of the β-lactamase was homologous to the AmpA sequences of the Serratia fonticola chromosomal enzyme (96%), MEN-1 (78%), Klebsiella oxytoca chromosomal enzymes (77%), TOHO-1 (75%), and FEC-1 (72%). The conserved sequences of class A β-lactamases, including the S-X(T)-X(S)-K motif, in the active site were all conserved in this enzyme. On the basis of the high degree of homology to the β-lactamase of S. fonticola, the enzyme was named SFO-1. The ampR gene was located upstream of the ampA gene, and the AmpR sequence of SFO-1 had homology with the AmpR sequences of the chromosomal β-lactamases from Citrobacter diversus(80%), Proteus vulgaris (68%), and Pseudomonas aeruginosa (60%). SFO-1 was also inducible in E. coli. However, a transformant harboring plasmid without intactampR produced a small amount of β-lactamase constitutively, suggesting that AmpR works as an activator ofampA of SFO-1. This is the first report from Japan describing an inducible plasmid-mediated class A β-lactamase in gram-negative bacteria.
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2

Pradel, N., J. Delmas, L. F. Wu, C. L. Santini, and R. Bonnet. "Sec- and Tat-Dependent Translocation of β-Lactamases across the Escherichia coli Inner Membrane." Antimicrobial Agents and Chemotherapy 53, no. 1 (November 3, 2008): 242–48. http://dx.doi.org/10.1128/aac.00642-08.

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ABSTRACT β-Lactamases represent the major resistance mechanism of gram-negative bacteria against β-lactam antibiotics. The amino acid sequences of these proteins vary widely, but all are located in the periplasm of bacteria. In this study, we investigated the translocation mechanism of representative β-lactamases in an Escherichia coli model. N-terminal signal sequence analyses, antibiotic activity assay, and direct measurement of translocation of a green fluorescent protein (GFP) reporter fused to β-lactamases revealed that most were exported via the Sec pathway. However, the Stenotrophomonas maltophilia L2 β-lactamase was exported via the E. coli Tat translocase, while the S. maltophilia L1 β-lactamase was Sec dependent. These results show the possible Tat-dependent translocation of β-lactamases in the E. coli model system. In addition, the mutation of the cytoskeleton-encoding gene mreB, which may be involved in the spatial organization of penicillin-binding proteins, decreased the MIC of β-lactams for β-lactamase-producing E. coli. These findings provide new knowledge about β-lactamase translocation, a putative new target for addressing β-lactamase-mediated resistance.
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3

Lau, Susanna K. P., Pak-leung Ho, Maria W. S. Li, Hoi-wah Tsoi, Raymond W. H. Yung, Patrick C. Y. Woo, and Kwok-yung Yuen. "Cloning and Characterization of a Chromosomal Class C β-Lactamase and Its Regulatory Gene in Laribacter hongkongensis." Antimicrobial Agents and Chemotherapy 49, no. 5 (May 2005): 1957–64. http://dx.doi.org/10.1128/aac.49.5.1957-1964.2005.

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ABSTRACT Laribacter hongkongensis, a newly discovered bacterium recently shown to be associated with community-acquired gastroenteritis, is generally resistant to most β-lactams except the carbapenems. We describe the cloning and characterization of a novel chromosomal class C β-lactamase and its regulatory gene in L. hongkongensis. Two genes, ampC and ampR, were cloned by inserting restriction fragments of genomic DNA from L. hongkongensis strain HLHK5 into pBK-CMV to give the recombinant plasmid pBK-LHK-5. The ampR and ampC genes and their promoters were divergently oriented, with the ampR gene immediately upstream of the ampC gene and an intercistronic Lys-R motif, typical of inducible ampC-ampR regulatory systems. The deduced amino acid sequence of the cloned AmpC β-lactamase (pI 8.1) contained consensus motifs characteristic of class C β-lactamases but had identities no greater than 46% to known class C β-lactamases. The kinetic properties of this AmpC were also compatible with those of a class C β-lactamase. PCR of 20 clinical isolates of L. hongkongensis, including HLHK5, showed the presence of both ampC and ampR genes in all isolates. Southern hybridization suggested that the ampC gene of HLHK5 was chromosomally encoded. Subcloning experiments showed that the expression of the ampC gene of HLHK5 was regulated by its ampR gene, which acts as a repressor. The β-lactamase characterized from strain HLHK5 was named LHK-5 (gene, bla LHK-5) and represents the first example of AmpC β-lactamase in the β subdivision of proteobacteria.
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4

Fournier, B., and P. H. Roy. "Variability of chromosomally encoded beta-lactamases from Klebsiella oxytoca." Antimicrobial Agents and Chemotherapy 41, no. 8 (August 1997): 1641–48. http://dx.doi.org/10.1128/aac.41.8.1641.

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The beta-lactamase genes of Klebsiella oxytoca were previously divided into two main groups: bla(OXY-1) and bla(OXY-2). The two beta-lactamase groups were each represented by beta-lactamases with four different pIs. In each group, one form of beta-lactamase is more frequent than the others combined. The beta-lactamase gene of each representative beta-lactamase with a different pI that was not yet sequenced (pIs 5.7, 6.8 [OXY-2], 7.1, 8.2, and 8.8 [OXY-1]) was cloned and sequenced. The susceptibility patterns as well as relative rates and kinetic parameters for beta-lactam hydrolysis revealed that OXY-2 enzymes hydrolyzed several of the beta-lactams that were examined (carbenicillin, cephalothin, cefamandole, ceftriaxone, and aztreonam) at a greater rate than the OXY-1 enzymes did. Comparison of K. oxytoca beta-lactamases with plasmid-mediated extended-spectrum beta-lactamases MEN-1 and TOHO-1 implied that the threonine at position 168 present in OXY-2 beta-lactamase instead of the alanine in OXY-1 could be responsible for its modified substrate hydrolysis. In each group, the beta-lactamase with a variant pI differs from the main form of beta-lactamase by one to five amino acid substitutions. The substrate profile and the 50% inhibitory concentrations revealed that all substitutions differing from the main form of beta-lactamase were neutral except one difference in the OXY-1 group. This substitution of an Ala to a Gly at position 237 increases the hydrolysis of some beta-lactams, particularly aztreonam; decreases the hydrolysis of benzylpenicillin, cephaloridine, and cefamandole, and decreases the susceptibility to clavulanic acid (fivefold increase in the 50% inhibitory concentration).
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5

Ma, Ling, Yoshikazu Ishii, Masaji Ishiguro, Hiroshi Matsuzawa, and Keizo Yamaguchi. "Cloning and Sequencing of the Gene Encoding Toho-2, a Class A β-Lactamase Preferentially Inhibited by Tazobactam." Antimicrobial Agents and Chemotherapy 42, no. 5 (May 1, 1998): 1181–86. http://dx.doi.org/10.1128/aac.42.5.1181.

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ABSTRACT Escherichia coli TUM1083, which is resistant to ampicillin, carbenicillin, cephaloridine, cephalothin, piperacillin, cefuzonam, and aztreonam while being sensitive to cefoxitin, moxalactam, cefmetazole, ceftazidime, and imipenem, was isolated from the urine of a patient treated with β-lactam antibiotics. The β-lactamase (Toho-2) purified from the bacteria hydrolyzed β-lactam antibiotics such as penicillin G, carbenicillin, cephaloridine, cefoxitin, cefotaxime, ceftazidime, and aztreonam and especially had increased relative hydrolysis rates for cephalothin, cephaloridine, cefotaxime, and ceftizoxime. Different from other extended-spectrum β-lactamases, Toho-2 was inhibited 16-fold better by the β-lactamase inhibitor tazobactam than by clavulanic acid. Resistance to β-lactams was transferred by conjugation from E. coliTUM1083 to E. coli ML4909, and the transferred plasmid was about 54.4 kbp, belonging to the incompatibility group IncFII. The cefotaxime resistance gene for Toho-2 was subcloned from the 54.4-kbp plasmid. The sequence of the gene was determined, and the open reading frame of the gene was found to consist of 981 bases. The nucleotide sequence of the gene (DDBJ accession no. D89862) designated asbla toho was found to have 76.3% identity to class A β-lactamase CTX-M-2 and 76.2% identity to Toho-1. It has 55.9% identity to SHV-1 β-lactamase and 47.5% identity to TEM-1 β-lactamase. Therefore, the newly isolated β-lactamase designated as Toho-2 produced by E. coli TUM1083 is categorized as an enzyme similar to Toho-1 group β-lactamases rather than to mutants of TEM or SHV enzymes. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 327 amino acid residues. Comparison of Toho-2 with other β-lactamase (non-Toho-1 group) suggests that the substitutions of threonine for Arg-244 and arginine for Asn-276 are important for the extension of the substrate specificity.
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6

Gazouli, Maria, Eva Tzelepi, Sergei V. Sidorenko, and Leonidas S. Tzouvelekis. "Sequence of the Gene Encoding a Plasmid-Mediated Cefotaxime-Hydrolyzing Class A β-Lactamase (CTX-M-4): Involvement of Serine 237 in Cephalosporin Hydrolysis." Antimicrobial Agents and Chemotherapy 42, no. 5 (May 1, 1998): 1259–62. http://dx.doi.org/10.1128/aac.42.5.1259.

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ABSTRACT The sequence of the gene encoding a novel cefotaxime-hydrolyzing β-lactamase (CTX-M-4) was determined. It was located in a plasmid harbored by a Salmonella typhimurium strain. CTX-M-4 was similar to the plasmidic cefotaxime-hydrolyzing β-lactamases CTX-M-2 and Toho-1 and related to the chromosomal β-lactamase ofKlebsiella oxytoca. A Ser-237→Ala substitution, introduced by site-directed mutagenesis, caused minor alterations in the interaction of CTX-M-4 with β-lactams, reducing slightly the relative hydrolytic activity against cefotaxime and the susceptibility to inhibition by clavulanate.
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7

Queenan, Anne Marie, Stephen Jenkins, and Karen Bush. "Cloning and Biochemical Characterization of FOX-5, an AmpC-Type Plasmid-Encoded β-Lactamase from a New York CityKlebsiella pneumoniae Clinical Isolate." Antimicrobial Agents and Chemotherapy 45, no. 11 (November 1, 2001): 3189–94. http://dx.doi.org/10.1128/aac.45.11.3189-3194.2001.

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ABSTRACT Klebsiella pneumoniae 5064, isolated in New York, carried plasmid-mediated resistance to multiple β-lactams and was unresponsive to clavulanic acid. The β-lactamase gene responsible for cephalosporin resistance encoded FOX-5, with 96 to 97% amino acid identities to other members of the FOX family of β-lactamases. Thebla FOX-5 coding region was located next to a transposase gene from the Aeromonas salmonicidainsertion element ISAS2.
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8

Walsh, Timothy R., Mark A. Toleman, Laurent Poirel, and Patrice Nordmann. "Metallo-β-Lactamases: the Quiet before the Storm?" Clinical Microbiology Reviews 18, no. 2 (April 2005): 306–25. http://dx.doi.org/10.1128/cmr.18.2.306-325.2005.

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SUMMARY The ascendancy of metallo-β-lactamases within the clinical sector, while not ubiquitous, has nonetheless been dramatic; some reports indicate that nearly 30% of imipenem-resistant Pseudomonas aeruginosa strains possess a metallo-β-lactamase. Acquisition of a metallo-β-lactamase gene will invariably mediate broad-spectrum β-lactam resistance in P. aeruginosa, but the level of in vitro resistance in Acinetobacter spp. and Enterobacteriaceae is less dependable. Their clinical significance is further embellished by their ability to hydrolyze all β-lactams and by the fact that there is currently no clinical inhibitor, nor is there likely to be for the foreseeable future. The genes encoding metallo-β-lactamases are often procured by class 1 (sometimes class 3) integrons, which, in turn, are embedded in transposons, resulting in a highly transmissible genetic apparatus. Moreover, other gene cassettes within the integrons often confer resistance to aminoglycosides, precluding their use as an alternative treatment. Thus far, the metallo-β-lactamases encoded on transferable genes include IMP, VIM, SPM, and GIM and have been reported from 28 countries. Their rapid dissemination is worrisome and necessitates the implementation of not just surveillance studies but also metallo-β-lactamase inhibitor studies securing the longevity of important anti-infectives.
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9

Madinier, I., T. Fosse, J. Giudicelli, and R. Labia. "Cloning and Biochemical Characterization of a Class A β-Lactamase from Prevotella intermedia." Antimicrobial Agents and Chemotherapy 45, no. 8 (August 1, 2001): 2386–89. http://dx.doi.org/10.1128/aac.45.8.2386-2389.2001.

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ABSTRACT The gene encoding a β-lactamase of Prevotella intermedia was cloned and sequenced. This gene, calledcfxA2, shared 98% identity with cfxA, the structural gene of a β-lactamase previously described inBacteroides vulgatus. The deduced protein sequence had a K272E substitution. CfxA2 had the characteristics of class A, group 2e β-lactamases.
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10

Moubareck, Carole, Sylvie Brémont, Marie-Christine Conroy, Patrice Courvalin, and Thierry Lambert. "GES-11, a Novel Integron-Associated GES Variant in Acinetobacter baumannii." Antimicrobial Agents and Chemotherapy 53, no. 8 (May 18, 2009): 3579–81. http://dx.doi.org/10.1128/aac.00072-09.

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ABSTRACT New extended-spectrum β-lactamase GES-11 was detected in Acinetobacter baumannii BM4674. The enzyme conferred resistance to β-lactams, including aztreonam, and reduced susceptibility to carbapenems. The structural gene was part of a class 1 integron borne by self-transferable plasmid pIP847. GES-type β-lactamases have not been reported previously in A. baumannii.
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11

Ye, Ying, Xi-Hai Xu, and Jia-Bin Li. "Emergence of CTX-M-3, TEM-1 and a new plasmid-mediated MOX-4 AmpC in a multiresistant Aeromonas caviae isolate from a patient with pneumonia." Journal of Medical Microbiology 59, no. 7 (July 1, 2010): 843–47. http://dx.doi.org/10.1099/jmm.0.016337-0.

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Aeromonas species rarely cause pulmonary infection. We report, for what is believed to be the first time, a case of severe pneumonia in a cancer patient caused by Aeromonas caviae. Detailed microbiological investigation revealed that this isolate carried three β-lactamase-encoding genes (encoding MOX-4, CTX-M-3 and TEM-1) conferring resistance to all β-lactams but imipenem. The β-lactamase with a pI of 9.0 was transferred by conjugation and associated with a 7.3 kb plasmid, as demonstrated by Southern blot hybridization. Analysis of the nucleotide and amino acid sequences showed a new ampC gene that was closely related to those encoding the MOX-1, MOX-2 and MOX-3 β-lactamases. This new plasmid-mediated AmpC β-lactamase from China was named MOX-4. This is believed to be the first report of MOX-4, CTX-M-3 and TEM-1 β-lactamases in a multiresistant A. caviae.
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12

Nadjar, David, Roger Labia, Claude Cerceau, Chantal Bizet, Alain Philippon, and Guillaume Arlet. "Molecular Characterization of Chromosomal Class C β-Lactamase and Its Regulatory Gene in Ochrobactrum anthropi." Antimicrobial Agents and Chemotherapy 45, no. 8 (August 1, 2001): 2324–30. http://dx.doi.org/10.1128/aac.45.8.2324-2330.2001.

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ABSTRACT Ochrobactrum anthropi, formerly known as CDC group Vd, is an oxidase-producing, gram-negative, obligately aerobic, non-lactose-fermenting bacillus of low virulence that occasionally causes human infections. It is highly resistant to all β-lactams except imipenem. A clinical isolate, SLO74, and six reference strains were tested. MICs of penicillins, aztreonam, and most cephalosporins tested, including cefotaxime and ceftazidime, were >128 μg/ml and of cefepime were 64 to >128 μg/ml. Clavulanic acid was ineffective and tazobactam had a weak effect in association with piperacillin. Two genes, ampR and ampC, were cloned by inserting restriction fragments of genomic DNA from the clinical strain O. anthropi SLO74 into pBK-CMV to give the recombinant plasmid pBK-OA1. The pattern of resistance to β-lactams of this clone was similar to that of the parental strain, except for its resistance to cefepime (MIC, 0.5 μg/ml). The deduced amino acid sequence of the AmpC β-lactamase (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded class C β-lactamases. The kinetic properties of this β-lactamase were typical for this class of β-lactamases. Upstream from the ampC gene, the ampR gene encodes a protein with a sequence that is 46 to 62% identical to those of other AmpR proteins and with an amino-terminal DNA-binding domain typical of transcriptional activators of the Lys-R family. The deduced amino acid sequences of theampC genes of the six reference strains were 96 to 99% identical to the sequence of the clinical strain. The β-lactamase characterized from strain SLO74 was named OCH-1 (gene, bla OCH-I).
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13

Bou, Germán, and Jesús Martínez-Beltrán. "Cloning, Nucleotide Sequencing, and Analysis of the Gene Encoding an AmpC β-Lactamase in Acinetobacter baumannii." Antimicrobial Agents and Chemotherapy 44, no. 2 (February 1, 2000): 428–32. http://dx.doi.org/10.1128/aac.44.2.428-432.2000.

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ABSTRACT A clinical strain of Acinetobacter baumannii (strain Ab RYC 52763/97) that was isolated during an outbreak in our hospital and that was resistant to all β-lactam antibiotics tested produced three β-lactamases: a TEM-1-type (pI, 5.4) plasmid-mediated β-lactamase, a chromosomally mediated OXA-derived (pI, 9.0) β-lactamase, and a presumptive chromosomal cephalosporinase (pI, 9.4). The nucleotide sequence of the chromosomal cephalosporinase gene shows for the first time the gene encoding an AmpC β-lactamase in A. baumannii. In addition, we report here the biochemical properties of this A. baumannii AmpC β-lactamase.
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14

Matsumoto, Takehisa, Mika Nagata, Nau Ishimine, Kenji Kawasaki, Kazuyoshi Yamauchi, Eiko Hidaka, Eriko Kasuga, et al. "Characterization of CIA-1, an Ambler Class A Extended-Spectrum β-Lactamase from Chryseobacterium indologenes." Antimicrobial Agents and Chemotherapy 56, no. 1 (November 14, 2011): 588–90. http://dx.doi.org/10.1128/aac.05165-11.

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ABSTRACTAn Ambler class A β-lactamase gene,blaCIA-1, was cloned from the reference strainChryseobacterium indologenesATCC 29897 and expressed inEscherichia coliBL21. TheblaCIA-1gene encodes a novel extended-spectrum β-lactamase (ESBL) that shared 68% and 60% identities with the CGA-1 and CME-1 β-lactamases, respectively.blaCIA-1-like genes were detected from clinical isolates. In addition to the metallo-β-lactamase IND of Ambler class B,C. indologeneshas a class A ESBL gene,blaCIA-1, located on the chromosome.
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15

Giakkoupi, Panagiota, Leonidas S. Tzouvelekis, Athanassios Tsakris, Veneta Loukova, Danai Sofianou, and Eva Tzelepi. "IBC-1, a Novel Integron-Associated Class A β-Lactamase with Extended-Spectrum Properties Produced by anEnterobacter cloacae Clinical Strain." Antimicrobial Agents and Chemotherapy 44, no. 9 (September 1, 2000): 2247–53. http://dx.doi.org/10.1128/aac.44.9.2247-2253.2000.

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ABSTRACT A transferable β-lactamase produced by a multidrug-resistant clinical isolate of Enterobacter cloacae was studied. Thebla gene was carried by a large (>80-kb) transmissible plasmid. Nucleotide sequence analysis of cloned fragments revealed that it was part of a gene cassette carried by a class 1 integron along with other resistance genes, includingaac(6′)-Ib. The encoded β-lactamase, designated IBC-1, was a novel class A enzyme that hydrolyzed ceftazidime and cefotaxime and was inhibited by tazobactam and, to a lesser extent, by clavulanate. Also, imipenem exhibited potent inhibitory activity against IBC-1. The enzyme consisted of 287 amino acid residues, including Ser-237, cysteines at positions 69 and 237a, and Arg-244, which may be implicated in its interaction with β-lactams. In amino acid sequence comparisons, IBC-1 displayed the highest similarity with the chromosomal penicillinase of Yersinia enterocolitica, a carbenicillinase from Proteus mirabilis GN79, the species-specific β-lactamases ofKlebsiella oxytoca, and the carbapenemase Sme-1. However, a phylogenetic association with established β-lactamase clusters could not be conclusively shown.
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16

Voladri, Rama Kishan R., and Douglas S. Kernodle. "Characterization of a Chromosomal Gene Encoding Type B β-Lactamase in Phage Group II Isolates ofStaphylococcus aureus." Antimicrobial Agents and Chemotherapy 42, no. 12 (December 1, 1998): 3163–68. http://dx.doi.org/10.1128/aac.42.12.3163.

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ABSTRACT In contrast to most Staphylococcus aureus isolates in which the gene for staphylococcal β-lactamase (blaZ) is plasmid borne, isolates typeable by group II bacteriophages frequently carry blaZ on the chromosome. Furthermore, the chromosomal gene encodes the type B variant of staphylococcal β-lactamase for which the nucleotide and deduced amino acid sequences have not yet been reported. To better understand β-lactamase production among phage group II staphylococci and the nature of the type B β-lactamase, we determined the type and amount of enzyme produced by 24 phage group II isolates. Of these isolates, 1 did not produce β-lactamase, 8 produced the type B enzyme, and 15 produced the type C enzyme. In all eight type B β-lactamase-producing isolates, blaZ was located on the chromosome. This was in contrast to the type C β-lactamase-producing isolates, in which blaZ was located on a 21-kb plasmid. The nucleotide sequence corresponding to the leader peptide and the N-terminal 85% of the mature exoenzyme form of type BS. aureus was determined. The deduced amino acid sequence revealed 3 residues in the leader peptide and 12 residues in the exoenzyme portion of the β-lactamase that differ from the prototypic type A β-lactamase sequence. These include the serine-to-asparagine change at residue 216 found in the kinetically similar type C enzyme, a threonine-to-lysine change at residue 128 close to the SDN loop (residues 130 to 132), and several substitutions not found in any of the other staphylococcal β-lactamases. In summary, modern isolates ofS. aureus typeable by group II phages produce type B or type C staphylococcal β-lactamase. The type B gene resides on the chromosome and has a sequence that, when compared to the sequences of the other staphylococcal β-lactamases, corresponds well with its kinetic properties.
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17

Lodge, J. M., S. D. Minchin, L. J. V. Piddock, and S. J. W. Busby. "Cloning, sequencing and analysis of the structural gene and regulatory region of the Pseudomonas aeruginosa chromosomal ampCβ-lactamase." Biochemical Journal 272, no. 3 (December 15, 1990): 627–31. http://dx.doi.org/10.1042/bj2720627.

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The chromosomal gene from Pseudomonas aeruginosa encoding beta-lactamase has been cloned, and the sequence determined and compared with corresponding sequences of beta-lactamases from members of the enterobacteriaceae. Upstream of the beta-lactamase gene is an open reading frame which we postulate encodes a regulatory protein, AmpR. We identified a helix-turn-helix region in AmpR and a putative AmpR-binding site.
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18

Kim, Jungmin, Youngmi Kwon, Hyunjoo Pai, Jong-Won Kim, and Dong-Taek Cho. "Survey of Klebsiella pneumoniae Strains Producing Extended-Spectrum β-Lactamases: Prevalence of SHV-12 and SHV-2a in Korea." Journal of Clinical Microbiology 36, no. 5 (1998): 1446–49. http://dx.doi.org/10.1128/jcm.36.5.1446-1449.1998.

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Fifty-three clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae collected from three hospitals in Korea were investigated for phenotypical and genotypical characterizations. Among these, 39 strains (74%) were shown by isoelectric focusing to carry SHV-type β-lactamases: 27 strains showed the pI 8.2 β-lactamase, and another 12 strains showed the pI 7.6 β-lactamase. The SHV gene of each of these strains was amplified by PCR, followed by nucleotide sequencing analysis. The gene of the pI 8.2 β-lactamase was found to be identical to the sequences encoding SHV-12, and the gene of the pI 7.6 β-lactamase was identical to the sequences encoding SHV-2a. A total of eight cefoxitin-resistant strains were found to have the plasmid-mediated AmpC-type β-lactamase, with a pI of 8.0, and this was confirmed to be CMY-1 β-lactamase by PCR and hybridization analysis. Noteworthy in this study is the fact that SHV-12 and SHV-2a have been the most commonly identified SHV-type ESBLs in Korea.
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19

Poirel, Laurent, Claire Héritier, Venus Tolün, and Patrice Nordmann. "Emergence of Oxacillinase-Mediated Resistance to Imipenem in Klebsiella pneumoniae." Antimicrobial Agents and Chemotherapy 48, no. 1 (January 2004): 15–22. http://dx.doi.org/10.1128/aac.48.1.15-22.2004.

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ABSTRACT Klebsiella pneumoniae strain 11978 was isolated in Turkey in 2001 and was found to be resistant to all β-lactams, including carbapenems. Cloning and expression in Escherichia coli identified five β-lactamases, including two novel oxacillinases. The β-lactamase OXA-48 hydrolyzed imipenem at a high level and was remotely related (less than 46% amino acid identity) to the other oxacillinases. It hydrolyzed penicillins and imipenem but not expanded-spectrum cephalosporins. The bla OXA-48 gene was plasmid encoded and not associated with an integron, in contrast to most of the oxacillinase genes. An insertion sequence, IS1999, was found immediately upstream of bla OXA-48. Another plasmid that encoded a second oxacillinase gene, bla OXA-47, located inside a class 1 integron was identified in K. pneumoniae 11978. OXA-47 had a narrow spectrum of hydrolysis activity and did not hydrolyze ceftazidime or imipenem, as is found for the β-lactamase (OXA-1) to which it is related. In addition, β-lactamases TEM-1 and SHV-2a were expressed from the same K. pneumoniae isolate. Analysis of the outer membrane proteins of this isolate revealed that it lacked a porin of ca. 36 kDa. Thus, the high-level resistance to β-lactams of this clinical isolate resulted from peculiar β-lactamases and modification of outer membrane proteins.
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20

Diene, Seydina M., Lucile Pinault, Nicholas Armstrong, Said Azza, Vivek Keshri, Saber Khelaifia, Eric Chabrière, et al. "Dual RNase and β-lactamase Activity of a Single Enzyme Encoded in Archaea." Life 10, no. 11 (November 14, 2020): 280. http://dx.doi.org/10.3390/life10110280.

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β-lactam antibiotics have a well-known activity which disturbs the bacterial cell wall biosynthesis and may be cleaved by β-lactamases. However, these drugs are not active on archaea microorganisms, which are naturally resistant because of the lack of β-lactam target in their cell wall. Here, we describe that annotation of genes as β-lactamases in Archaea on the basis of homologous genes is a remnant of identification of the original activities of this group of enzymes, which in fact have multiple functions, including nuclease, ribonuclease, β-lactamase, or glyoxalase, which may specialized over time. We expressed class B β-lactamase enzyme from Methanosarcina barkeri that digest penicillin G. Moreover, while weak glyoxalase activity was detected, a significant ribonuclease activity on bacterial and synthetic RNAs was demonstrated. The β-lactamase activity was inhibited by β-lactamase inhibitor (sulbactam), but its RNAse activity was not. This gene appears to have been transferred to the Flavobacteriaceae group especially the Elizabethkingia genus, in which the expressed gene shows a more specialized activity on thienamycin, but no glyoxalase activity. The expressed class C-like β-lactamase gene, from Methanosarcina sp., also shows hydrolysis activity on nitrocefin and is more closely related to DD-peptidase enzymes. Our findings highlight the need to redefine the nomenclature of β-lactamase enzymes and the specification of multipotent enzymes in different ways in Archaea and bacteria over time.
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21

Haeggman, S., S. Löfdahl, and L. G. Burman. "An allelic variant of the chromosomal gene for class A beta-lactamase K2, specific for Klebsiella pneumoniae, is the ancestor of SHV-1." Antimicrobial Agents and Chemotherapy 41, no. 12 (December 1997): 2705–9. http://dx.doi.org/10.1128/aac.41.12.2705.

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Fecal Klebsiella isolates from neonates in 22 Swedish special care units were examined by a PCR we developed for detection of the SHV-1 beta-lactamase gene. All 105 K. pneumoniae isolates and all 11 K. pneumoniae reference strains (including the K. pneumoniae subsp. pneumoniae, ozaenae, and rhinoscleromatis type strains) tested were positive, whereas all 67 K. oxytoca isolates and the K. oxytoca, K. planticola, and K. terrigena type strains tested were negative. Resistance to beta-lactams in K. pneumoniae was not transferable by conjugation, and the beta-lactamase gene was never found on a plasmid. Southern blot analysis showed that the gene had a defined chromosomal location. Isoelectric focusing and sequencing of 231-bp PCR amplicons from different isolates revealed many variants of the enzyme, with the two main groups being SHV-1 like (pI 7.6; 68 isolates) and LEN-1 like (pI 7.1; 14 isolates). Clavulanic acid markedly reduced the MICs of ampicillin for all the K. pneumoniae isolates tested. This fact, MIC profiles (penicillin rather than cephalosporin resistance), pIs, and sequence data showed that the chromosomal beta-lactamase of K. pneumoniae is a class A, group 2 enzyme distinct from the chromosomal AmpC enzymes found in several other gram-negative bacteria and from the chromosomal beta-lactamase K1 of K. oxytoca. We propose that the chromosomal beta-lactamase of K. pneumoniae be designated K2 and suggest that an allelic pI 7.6 variant of this enzyme is the ancestor of the SHV family of plasmid-mediated beta-lactamases.
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22

Kim, In-Suk, Chang-Seok Ki, Sunjoo Kim, Won Sup Oh, Kyong Ran Peck, Jae-Hoon Song, Kyungwon Lee, and Nam Yong Lee. "Diversity of Ampicillin Resistance Genes and Antimicrobial Susceptibility Patterns in Haemophilus influenzae Strains Isolated in Korea." Antimicrobial Agents and Chemotherapy 51, no. 2 (November 20, 2006): 453–60. http://dx.doi.org/10.1128/aac.00960-06.

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ABSTRACT By Etest determination of the susceptibilities of 229 Haemophilus influenzae strains isolated in Korea to 10 antibiotics, the isolates were found to be antibiotic nonsusceptible in the following order: ampicillin (58.1%), trimethoprim-sulfamethoxazole (52%), cefaclor (41.1%), clarithromycin (25.8%), chloramphenicol (14.0%), amoxicillin-clavulanic acid (13.5%), meropenem (11.7%), cefixime (10.9%), cefuroxime (9.2%), and levofloxacin (1.3%). The prevalences of each resistance class were 23.6% for β-lactamase-negative ampicillin-susceptible (BLNAS) strains; 37.6% for strains with the TEM-1 type β-lactamase gene; 1.3% for strains with the ROB-1 type β-lactamase gene; 29.3% for the β-lactamase-negative ampicillin-resistant (BLNAR) strains with a mutation in the ftsI gene, which encodes PBP 3; and 8.3% for β-lactamase-positive amoxicillin-clavulanate-resistant (BLPACR) strains, which showed both resistance mechanisms (i.e., a β-lactamase gene and a mutation in the ftsI gene). The MIC50s of all β-lactams, including cephem and meropenem agents, for the BLNAR strains were two to three times higher than those for the BLNAS strains. This study confirms that the prevalence of BLNAR and BLPACR strains is relatively high and for the first time confirms the presence of H. influenzae strains carrying bla ROB-1 in Korea. Even though mutations in another gene(s) might be involved in β-lactam resistance, these results suggest that mutations in the ftsI gene are important for the development of resistance to β-lactams in H. influenzae strains in Korea.
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23

Voha, Christine, Jean-Denis Docquier, Gian Maria Rossolini, and Thierry Fosse. "Genetic and Biochemical Characterization of FUS-1 (OXA-85), a Narrow-Spectrum Class D β-Lactamase from Fusobacterium nucleatum subsp. polymorphum." Antimicrobial Agents and Chemotherapy 50, no. 8 (August 2006): 2673–79. http://dx.doi.org/10.1128/aac.00058-06.

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ABSTRACT Previous studies have reported β-lactamase-mediated penicillin resistance in Fusobacterium nucleatum, but no β-lactamase gene has yet been identified in this species. An F. nucleatum subsp. polymorphum strain resistant to penicillin and amoxicillin was isolated from a human periodontitis sample. DNA cloning and sequencing revealed a 765-bp open reading frame encoding a new class D β-lactamase named FUS-1 (OXA-85). A recombinant Escherichia coli strain carrying the bla FUS-1 gene exhibited resistance to amoxicillin with a moderate decrease in the MICs with clavulanic acid. The bla FUS-1 gene was found in two additional clonally unrelated F. nucleatum subsp. polymorphum isolates. It was located on the chromosome in a peculiar genetic environment where a gene encoding a putative transposase-like protein is found, suggesting a possible acquisition of this class D β-lactamase gene. The FUS-1 enzyme showed the closest ancestral relationship with OXA-63 from Brachyspira pilosicoli (53% identity) and with putative chromosomal β-lactamases of Campylobacter spp. (40 to 42% identity). FUS-1 presents all of the conserved structural motifs of class D β-lactamases. Kinetic analysis revealed that FUS-1 exhibits a narrow substrate profile, efficiently hydrolyzing benzylpenicillin and oxacillin. FUS-1 was poorly inactivated by clavulanate and NaCl. FUS-1 is the first example of a class D β-lactamase produced by a gram-negative, anaerobic, rod-shaped bacterium to be characterized.
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24

Poirel, Laurent, Peter Kämpfer, and Patrice Nordmann. "Chromosome-Encoded Ambler Class A β-Lactamase of Kluyvera georgiana, a Probable Progenitor of a Subgroup of CTX-M Extended-Spectrum β-Lactamases." Antimicrobial Agents and Chemotherapy 46, no. 12 (December 2002): 4038–40. http://dx.doi.org/10.1128/aac.46.12.4038-4040.2002.

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ABSTRACT A chromosome-encoded β-lactamase gene, cloned and expressed in Escherichia coli from Kluyvera georgiana reference strain CUETM 4246-74 (DSM 9408), encoded the extended-spectrum β-lactamase KLUG-1, which shared 99% amino acid identity with the plasmid-mediated β-lactamase CTX-M-8. This work provides further evidence that Kluyvera spp. may be the progenitor(s) of CTX-M-type β-lactamases.
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25

Bauernfeind, Adolf, Ines Schneider, Renate Jungwirth, Hany Sahly, and Uwe Ullmann. "A Novel Type of AmpC β-Lactamase, ACC-1, Produced by a Klebsiella pneumoniae Strain Causing Nosocomial Pneumonia." Antimicrobial Agents and Chemotherapy 43, no. 8 (August 1, 1999): 1924–31. http://dx.doi.org/10.1128/aac.43.8.1924.

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ABSTRACT A Klebsiella pneumoniae strain resistant to oxyimino cephalosporins was cultured from respiratory secretions of a patient suffering from nosocomial pneumonia in Kiel, Germany, in 1997. The isolate harbors a bla resistance gene located on a transmissible plasmid. An Escherichia coli transconjugant produces a β-lactamase with an isoelectric point of 7.7 and a resistance phenotype characteristic of an AmpC (class 1) β-lactamase except for low MICs of cephamycins. Thebla gene was cloned and sequenced. It encodes a protein of 386 amino acids with the active site serine of the S-X-X-K motif at position 64, as is characteristic for class C β-lactamases. Multiple alignment of the deduced amino acid sequence with 21 other AmpC β-lactamases demonstrates only very distant homology, reaching at maximum 52.3% identity for the chromosomal AmpC β-lactamase ofSerratia marcescens SR50. The β-lactamase ofK. pneumoniae KUS represents a new type of AmpC-class enzyme, for which we propose the designation ACC-1 (Ambler class C-1).
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26

Poirel, Laurent, Stéphane Corvec, Melina Rapoport, Pauline Mugnier, Alejandro Petroni, Fernando Pasteran, Diego Faccone, et al. "Identification of the Novel Narrow-Spectrum β-Lactamase SCO-1 in Acinetobacter spp. from Argentina." Antimicrobial Agents and Chemotherapy 51, no. 6 (April 9, 2007): 2179–84. http://dx.doi.org/10.1128/aac.01600-06.

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ABSTRACT By studying the β-lactamase content of several Acinetobacter spp. isolates from Argentina, producing the expanded-spectrum β-lactamases (ESBL) VEB-1a or PER-2, a novel Ambler class A β-lactamase gene was identified. It encoded the narrow-spectrum β-lactamase SCO-1, whose activity was inhibited by clavulanic acid. SCO-1 hydrolyzes penicillins at a high level and cephalosporins and carbapenems at a very low level. β-Lactamase SCO-1 was identified from unrelated VEB-1a-positive or PER-2-positive Acinetobacter spp. isolates recovered from three hospitals. The bla SCO-1 gene was apparently located on a plasmid of ca. 150 kb from all cases but was not associated with any ESBL-encoding gene. The G+C content of the bla SCO gene was 52%, a value that does not correspond to that of the A. baumannii genome (39%). β-Lactamase SCO-1 shares 47% amino acid identity with CARB-5 and ca. 40% with the enzymes TEM, SHV, and CTX-M. A gene encoding a putative resolvase was identified downstream of the bla SCO-1 gene, but its precise way of acquisition remains to be determined.
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27

Senda, K., Y. Arakawa, K. Nakashima, H. Ito, S. Ichiyama, K. Shimokata, N. Kato, and M. Ohta. "Multifocal outbreaks of metallo-beta-lactamase-producing Pseudomonas aeruginosa resistant to broad-spectrum beta-lactams, including carbapenems." Antimicrobial Agents and Chemotherapy 40, no. 2 (February 1996): 349–53. http://dx.doi.org/10.1128/aac.40.2.349.

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A total of 3,700 Pseudomonas aeruginosa isolates were collected from 17 general hospitals in Japan from 1992 to 1994. Of these isolates, 132 carbapenem-resistant strains were subjected to DNA hybridization analysis with the metallo-beta-lactamase gene (blaIMP)-specific probe. Fifteen strains carrying the metallo-beta-lactamase gene were identified in five hospitals in different geographical areas. Three strains of P. aeruginosa demonstrated high-level imipenem resistance (MIC, > or = 128 micrograms/ml), two strains exhibited low-level imipenem resistance (MIC, < or = 4 micrograms/ml), and the rest of the strains were in between. These results revealed that the acquisition of a metallo-beta-lactamase gene alone does not necessarily confer elevated resistance to carbapenems. In several strains, the metallo-beta-lactamase gene was carried by large plasmids, and carbapenem resistance was transferred from P. aeruginosa to Escherichia coli by electroporation in association with the acquisition of the large plasmid. Southern hybridization analysis and genomic DNA fingerprinting profiles revealed different genetic backgrounds for these 15 isolates, although considerable similarity was observed for the strains isolated from the same hospital. These findings suggest that the metallo-beta-lactamase-producing P. aeruginosa strains are not confined to a unique clonal lineage but proliferated multifocally by plasmid-mediated dissemination of the metallo-beta-lactamase gene in strains of different genetic backgrounds. Thus, further proliferation of metallo-beta-lactamase-producing strains with resistance to various beta-lactams may well be inevitable in the future, which emphasizes the need for early recognition of metallo-beta-lactamase-producing strains, rigorous infection control, and restricted clinical use of broad-spectrum beta-lactams including carbapenems.
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28

Poirel, Laurent, Jose-Manuel Rodríguez-Martínez, Nashwan Al Naiemi, Yvette J. Debets-Ossenkopp, and Patrice Nordmann. "Characterization of DIM-1, an Integron-Encoded Metallo-β-Lactamase from a Pseudomonas stutzeri Clinical Isolate in the Netherlands." Antimicrobial Agents and Chemotherapy 54, no. 6 (March 22, 2010): 2420–24. http://dx.doi.org/10.1128/aac.01456-09.

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ABSTRACT A carbapenem-resistant Pseudomonas stutzeri strain isolated from a Dutch patient was analyzed in detail. This isolate produced a metallo-β-lactamase (MBL) whose gene, with 43.5% GC content, was cloned and expressed in Escherichia coli. β-Lactamase DIM-1 (for Dutch imipenemase) was weakly related to other Ambler class B β-lactamases, sharing <52% amino acid identity with the most closely related MBL, GIM-1, and 45% identity with IMP-type MBLs. The β-Lactamase DIM-1 significantly hydrolyzed broad-spectrum cephalosporins and carbapenems and spared aztreonam. This MBL gene was embedded in a class 1 integron containing two other gene cassettes, encoding resistance to aminoglycosides and disinfectants, that was located on a 70-kb plasmid.
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29

Fournier, B., P. H. Roy, P. H. Lagrange, and A. Philippon. "Chromosomal beta-lactamase genes of Klebsiella oxytoca are divided into two main groups, blaOXY-1 and blaOXY-2." Antimicrobial Agents and Chemotherapy 40, no. 2 (February 1996): 454–59. http://dx.doi.org/10.1128/aac.40.2.454.

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The chromosomally encoded beta-lactamase gene (blaOXY-2) of the wild-type Klebsiella oxytoca SL911 was cloned and sequenced. Its nucleotide sequence similarity with the previously sequenced K. oxytoca beta-lactamase gene (blaOXY-1) (Y. Arakawa, M. Ohta, N. Kido, M. Mori, H. Ito, T. Komatsu, Y. Fujii, and N. Kato, Antimicrob. Agents Chemother. 33:63-70, 1989) is 87.3%, and its amino acid similarity is 89.7%. This group of K. oxytoca beta-lactamases is related to chromosomal beta-lactamases of Citrobacter diversus, Proteus vulgaris, and Yersinia enterocolitica and to the plasmid-mediated extended-spectrum beta-lactamases MEN-1 and Toho-1. By colony hybridization with 86 strains susceptible and resistant to aztreonam, isolated in six countries, K. oxytoca beta-lactamase genes hybridized with either a specific blaOXY-1 DNA probe (668 bp) or a blaOXY-2 DNA probe (723 bp). Thus, beta-lactamase genes could be divided into two groups: blaOXY-1 (47% of the strains) and blaOXY-2 (53% of the strains). A study of isoelectric points confirmed the great variability reported in the literature. However, the two beta-lactamase groups were each represented by four different pIs: for OXY-2, 5.2, 5.7, 6.4, and 6.8, with the 5.2 form representing 59% of all OXY-2 enzymes, and for OXY-1, 7.1, 7.5, 8.2, and 8.8, with the 7.5 form representing 88% of all OXY-1 enzymes.
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30

SADEGHI DEYLAMDEH, Zahra, and Abolfazl JAFARI SALES. "Evaluation of the presence of AmpC (FOX) beta-lactamase gene in clinical strains of Escherichia coli isolated from hospitalized patients in Tabriz, Iran." Journal of Experimental and Clinical Medicine 38, no. 3 (April 23, 2021): 301–4. http://dx.doi.org/10.52142/omujecm.38.3.17.

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Beta-lactamases are the most common cause of bacterial resistance to beta-lactam antibiotics. AmpC-type beta-lactamases hydrolyze cephalosporins, penicillins, and cephamycins. Therefore, the study aims was to determine antibiotic resistance and to investigate the presence of AmpC beta-lactamase gene in clinical strains of Escherichia coli isolated from hospitalized patients in Tabriz. In this cross-sectional descriptive study, 289 E. coli specimens were collected from clinical specimens. Disk diffusion method and combined disk method were used to determine the phenotype of extended spectrum β-Lactamase producing (ESBLs) strains. Then PCR was used to evaluate the presence of AmpC (FOX) beta-lactamase gene in the strains confirmed in phenotypic tests. Antibiotic resistance was also determined using disk diffusion by the Kibry-Bauer method. A total of 121 isolates were identified as generators of beta-lactamase genes. 72 (59.5 %) isolates producing ESBL and 49 (40.5 %) isolates were identified as AmpC generators. In the PCR test, 31 isolates contained the FOX gene. The highest resistance was related to the antibiotics amoxicillin (76.12%), ceftazidime (70.24%) and nalidixic acid (65.05%). The results indicate an increase in the prevalence of beta-lactamase genes and increased resistance to beta-lactam antibiotics, which can be the result of improper use of antibiotics and not using antibiotic susceptibility tests before starting treatment. Also, using phenotypic and molecular diagnostic methods such as PCR together can be very useful.
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31

Szabó, Dóra, Melissa A. Melan, Andrea M. Hujer, Robert A. Bonomo, Kristine M. Hujer, Christopher R. Bethel, Katalin Kristóf, and David L. Paterson. "Molecular Analysis of the Simultaneous Production of Two SHV-Type Extended-Spectrum Beta-Lactamases in a Clinical Isolate of Enterobacter cloacae by Using Single-Nucleotide Polymorphism Genotyping." Antimicrobial Agents and Chemotherapy 49, no. 11 (November 2005): 4716–20. http://dx.doi.org/10.1128/aac.49.11.4716-4720.2005.

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ABSTRACT Bacteria that simultaneously produce multiple extended-spectrum beta-lactamases are frequently isolated. We report an Enterobacter cloacae isolate, ES24, producing four different beta-lactamases (AmpC type beta-lactamase, TEM-1, SHV-7, and a novel extended-spectrum beta-lactamase, SHV-30). Direct sequencing of bla SHV gene products gave a “double peak” at position 703, suggesting the presence of more than one allele. Using fluorescence resonance energy transfer real-time PCR to detect single-nucleotide polymorphisms, we were able to distinguish two different bla SHV genes in a single isolate. This may prove to be a useful technique in surveys of beta-lactamase production in contemporary clinical isolates.
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32

Weng, Shu-Fen, Chun-Yi Chen, Yeong-Sheng Lee, Juey-Wen Lin, and Yi-Hsiung Tseng. "Identification of a Novel β-Lactamase Produced byXanthomonas campestris, a Phytopathogenic Bacterium." Antimicrobial Agents and Chemotherapy 43, no. 7 (July 1, 1999): 1792–97. http://dx.doi.org/10.1128/aac.43.7.1792.

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ABSTRACT The Xanthomonas campestris pv. campestris 11 chromosome encodes a periplasmic β-lactamase of 30 kDa. Gene replacement and complementation confirmed the presence of this enzyme. Its deduced amino acid sequence shows identity and conserved domains between it andStenotrophomonas maltophilia L2 and other Ambler class A/Bush group 2 β-lactamases. Southern hybridization detected a single homologous fragment in each of 12 other Xanthomonasstrains, indicating that the presence of a β-lactamase gene is common among xanthomonads.
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33

Gharout-Sait, Alima, Samer-Ahmed Alsharapy, Lucien Brasme, Abdelaziz Touati, Rachida Kermas, Sofiane Bakour, Thomas Guillard, and Christophe de Champs. "Enterobacteriaceae isolates carrying the New Delhi metallo-β-lactamase gene in Yemen." Journal of Medical Microbiology 63, no. 10 (October 1, 2014): 1316–23. http://dx.doi.org/10.1099/jmm.0.073767-0.

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Ten carbapenem-resistant Enterobacteriaceae (eight Klebsiella pneumoniae isolates and two Enterobacter cloacae) isolates from Yemen were investigated using in vitro antimicrobial susceptibility testing, phenotypic carbapenemase detection, multilocus sequence typing (MLST) and replicon typing. Carbapenemase, extended-spectrum β-lactamase (ESBL) and plasmid-mediated quinolone resistance determinant genes were identified using PCR and sequencing. All of the 10 carbapenem-resistant Enterobacteriaceae were resistant to β-lactams, tobramycin, ciprofloxacin and cotrimoxazole. Imipenem, doripenem and meropenem MICs ranged from 2 to >32 mg l−1 and ertapenem MICs ranged from 6 to >32 mg l−1. All of the K. pneumoniae isolates showed ESBL activity in phenotypic tests. Genes encoding bla NDM were detected in all strains. All K. pneumoniae strains produced CTX-M-15 ESBL and SHV β-lactamases. TEM-1 β-lactamase was detected in seven isolates. Nine isolates were qnr positive including QnrB1, QnrA1 and QnrS1, and six isolates produced AAC-6′-Ib-cr. MLST identified five different sequence types (STs): ST1399, ST147, ST29, ST405 and ST340. Replicon typing showed the presence of IncFII1K plasmids in four transformants. To the best of our knowledge, this is the first report of NDM-1-producing Enterobacteriaceae isolates in Yemen.
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34

MA, JIANMIN, FRANK EISENHABER, and SEBASTIAN MAURER-STROH. "AUTOMATIC PHYLOGENETIC CLASSIFICATION OF BACTERIAL BETA-LACTAMASE SEQUENCES INCLUDING STRUCTURAL AND ANTIBIOTIC SUBSTRATE PREFERENCE INFORMATION." Journal of Bioinformatics and Computational Biology 11, no. 06 (December 2013): 1343011. http://dx.doi.org/10.1142/s0219720013430117.

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Beta lactams comprise the largest and still most effective group of antibiotics, but bacteria can gain resistance through different beta lactamases that can degrade these antibiotics. We developed a user friendly tree building web server that allows users to assign beta lactamase sequences to their respective molecular classes and subclasses. Further clinically relevant information includes if the gene is typically chromosomal or transferable through plasmids as well as listing the antibiotics which the most closely related reference sequences are known to target and cause resistance against. This web server can automatically build three phylogenetic trees: the first tree with closely related sequences from a Tachyon search against the NCBI nr database, the second tree with curated reference beta lactamase sequences, and the third tree built specifically from substrate binding pocket residues of the curated reference beta lactamase sequences. We show that the latter is better suited to recover antibiotic substrate assignments through nearest neighbor annotation transfer. The users can also choose to build a structural model for the query sequence and view the binding pocket residues of their query relative to other beta lactamases in the sequence alignment as well as in the 3D structure relative to bound antibiotics. This web server is freely available at http://blac.bii.a-star.edu.sg/ .
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35

Martínez-Martínez, Luis, Alvaro Pascual, Santiago Hernández-Allés, Dolores Alvarez-Díaz, Ana Isabel Suárez, John Tran, Vicente Javier Benedí, and George A. Jacoby. "Roles of β-Lactamases and Porins in Activities of Carbapenems and Cephalosporins against Klebsiella pneumoniae." Antimicrobial Agents and Chemotherapy 43, no. 7 (July 1, 1999): 1669–73. http://dx.doi.org/10.1128/aac.43.7.1669.

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ABSTRACT Two clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae were noted to be less susceptible than expected to imipenem. Both were missing outer membrane proteins that serve as channels for antibiotic entry. The role of β-lactamase in resistance was investigated by eliminating the original ESBL and introducing plasmids encoding various ESBLs and AmpC β-lactamase types, by studying the effect of an increased inoculum, and by evaluating interactions with β-lactamase inhibitors. The contribution of porin deficiency was investigated by restoring a functional ompK36 gene on a plasmid. Plasmids encoding AmpC-type β-lactamases provided resistance to imipenem (up to 64 μg/ml) and meropenem (up to 16 μg/ml) in strains deficient in porins. Carbapenem resistance showed little inoculum effect, was not affected by clavulanate but was blocked by BRL 42715, and was diminished if OmpK36 porin was restored. Plasmids encoding TEM- and SHV-type ESBLs conferred resistance to cefepime and cefpirome, as well as to earlier oxyimino-β-lactams. This resistance was magnified with an increased inoculum, was blocked by clavulanate, and was also lowered by OmpK36 porin restoration. In addition, SHV-2 β-lactamase had a small effect on carbapenem resistance (imipenem MIC, 4 μg/ml, increasing to 16 μg/ml with a higher inoculum) when porins were absent. In K. pneumoniae porin loss can thus augment resistance provided either by TEM- or SHV-type ESBLs or by plasmid-mediated AmpC enzymes to include the latest oxyimino-β-lactams and carbapenems.
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36

Hu, Rouh-Mei, Kai-Hung Chiang, Yi-Chih Chang, and Tsuey-Ching Yang. "Characterization of the charge variants of L2 β-lactamase in Stenotrophomonas maltophilia." Journal of Medical Microbiology 58, no. 3 (March 1, 2009): 318–21. http://dx.doi.org/10.1099/jmm.0.000380-0.

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Stenotrophomonas maltophilia KH has two acid β-lactamases with isoelectric points (pIs) of 4.6 and 5.4, and several basic β-lactamases (pIs >7.0) that produce a ladder-shaped pattern by IEF. An isogenic L2 mutant, KHL2xylE, was constructed by gene replacement. From IEF and native PAGE zymograms of strains KH and KHL2xylE, it was demonstrated that the basic β-lactamases and the acid β-lactamase with pI 5.4 are encoded by the same L2 gene and that the active types of these L2 charge variants were dependent on the buffer pH. The β-lactamase activities of these L2 charge variants in phosphate buffer at pH 7.0 and 8.0 were 1075±29 and 1114±81 U mg−1, respectively. These results indicate that L2 charge variants give S. maltophilia a better chance of adapting and surviving in response to changes in the environment.
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37

Silva, J., C. Aguilar, G. Ayala, M. A. Estrada, U. Garza-Ramos, R. Lara-Lemus, and L. Ledezma. "TLA-1: a New Plasmid-Mediated Extended-Spectrum β-Lactamase from Escherichia coli." Antimicrobial Agents and Chemotherapy 44, no. 4 (April 1, 2000): 997–1003. http://dx.doi.org/10.1128/aac.44.4.997-1003.2000.

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ABSTRACT Escherichia coli R170, isolated from the urine of an infected patient, was resistant to expanded-spectrum cephalosporins, aztreonam, ciprofloxacin, and ofloxacin but was susceptible to amikacin, cefotetan, and imipenem. This particular strain contained three different plasmids that encoded two β-lactamases with pIs of 7.0 and 9.0. Resistance to cefotaxime, ceftazidime, aztreonam, trimethoprim, and sulfamethoxazole was transferred by conjugation from E. coli R170 to E. coli J53-2. The transferred plasmid, RZA92, which encoded a single β-lactamase, was 150 kb in length. The cefotaxime resistance gene that encodes the TLA-1 β-lactamase (pI 9.0) was cloned from the transconjugant by transformation to E. coli DH5α. Sequencing of thebla TLA-1 gene revealed an open reading frame of 906 bp, which corresponded to 301 amino acid residues, including motifs common to class A β-lactamases: 70SXXK,130SDN, and 234KTG. The amino acid sequence of TLA-1 shared 50% identity with the CME-1 chromosomal class A β-lactamase from Chryseobacterium(Flavobacterium) meningosepticum; 48.8% identity with the VEB-1 class A β-lactamase from E. coli; 40 to 42% identity with CblA of Bacteroides uniformis, PER-1 of Pseudomonas aeruginosa, and PER-2 ofSalmonella typhimurium; and 39% identity with CepA ofBacteroides fragilis. The partially purified TLA-1 β-lactamase had a molecular mass of 31.4 kDa and a pI of 9.0 and preferentially hydrolyzed cephaloridine, cefotaxime, cephalothin, benzylpenicillin, and ceftazidime. The enzyme was markedly inhibited by sulbactam, tazobactam, and clavulanic acid. TLA-1 is a new extended-spectrum β-lactamase of Ambler class A.
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38

Tribuddharat, Chanwit, Richard A. Moore, Patricia Baker, and Donald E. Woods. "Burkholderia pseudomallei Class A β-Lactamase Mutations That Confer Selective Resistance against Ceftazidime or Clavulanic Acid Inhibition." Antimicrobial Agents and Chemotherapy 47, no. 7 (July 2003): 2082–87. http://dx.doi.org/10.1128/aac.47.7.2082-2087.2003.

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ABSTRACT Burkholderia pseudomallei, the causative agent of melioidosis, is inherently resistant to a variety of antibiotics including aminoglycosides, macrolides, polymyxins, and β-lactam antibiotics. Despite resistance to many β-lactams, ceftazidime and β-lactamase inhibitor-β-lactam combinations are commonly used for treatment of melioidosis. Here, we examine the enzyme kinetics of β-lactamase isolated from mutants resistant to ceftazidime and clavulanic acid inhibition and describe specific mutations within conserved motifs of the β-lactamase enzyme which account for these resistance patterns. Sequence analysis of regions flanking the B. pseudomallei penA gene revealed a putative regulator gene located downstream of penA. We have cloned and sequenced the penA gene from B. mallei and found it to be identical to penA from B. pseudomallei.
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Rossolini, Gian Maria, Nicola Franceschini, Laura Lauretti, Berardo Caravelli, Maria Letizia Riccio, Moreno Galleni, Jean-Marie Frère, and Gianfranco Amicosante. "Cloning of a Chryseobacterium(Flavobacterium) meningosepticum Chromosomal Gene (blaACME) Encoding an Extended-Spectrum Class A β-Lactamase Related to the BacteroidesCephalosporinases and the VEB-1 and PER β-Lactamases." Antimicrobial Agents and Chemotherapy 43, no. 9 (September 1, 1999): 2193–99. http://dx.doi.org/10.1128/aac.43.9.2193.

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ABSTRACT In addition to the BlaB metallo-β-lactamase,Chryseobacterium (Flavobacterium)meningosepticum CCUG 4310 (NCTC 10585) constitutively produces a 31-kDa active-site serine β-lactamase, named CME-1, with an alkaline isoelectric pH. The blaA CME gene that encodes the latter enzyme was isolated from a genomic library constructed in the Escherichia coli plasmid vector pACYC184 by screening for cefuroxime-resistant clones. Sequence analysis revealed that the CME-1 enzyme is a new class A β-lactamase structurally divergent from the other members of this class, being most closely related to the VEB-1 (also named CEF-1) and PER β-lactamases and the Bacteroides chromosomal cephalosporinases. TheblaA CME determinant is located on the chromosome and exhibits features typical of those of C. meningosepticum resident genes. The CME-1 protein was purified from an E. coli strain that overexpresses the cloned gene via a T7-based expression system by means of an anion-exchange chromatography step followed by a gel permeation chromatography step. Kinetic parameters for several substrates were determined. CME-1 is a clavulanic acid-susceptible extended-spectrum β-lactamase that hydrolyzes most cephalosporins, penicillins, and monobactams but that does not hydrolyze cephamycins and carbapenems. The enzyme exhibits strikingly different kinetic parameters for different classes of β-lactams, with both Km andk cat values much higher for cephalosporins than for penicillins and monobactams. However, the variability of both kinetic parameters resulted in overall similar acylation rates (k cat/Km ratios) for all types of β-lactam substrates.
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40

Walckenaer, Estelle, Laurent Poirel, Véronique Leflon-Guibout, Patrice Nordmann, and Marie-Hélène Nicolas-Chanoine. "Genetic and Biochemical Characterization of the Chromosomal Class A β-Lactamases of Raoultella (formerly Klebsiella) planticola and Raoultella ornithinolytica." Antimicrobial Agents and Chemotherapy 48, no. 1 (January 2004): 305–12. http://dx.doi.org/10.1128/aac.48.1.305-312.2004.

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ABSTRACT Enterobacterial strains of Raoultella spp. display a penicillinase-related β-lactam resistance pattern suggesting the presence of a chromosomal bla gene. From whole-cell DNA of Raoultella planticola strain ATCC 33531T and Raoultella ornithinolytica strain ATCC 31898T, bla genes were cloned and expressed into Escherichia coli. Each gene encoded an Ambler class A β-lactamase, named PLA-1 and ORN-1 for R. planticola and R. ornithinolytica, respectively. These β-lactamases (291 amino acids), with the same pI value of 7.8, had a shared amino acid identity of 94%, 37 to 47% identity with the majority of the chromosome-encoded class A β-lactamases previously described for Enterobacteriaceae, and 66 to 69% identity with the two β-lactamases LEN-1 and SHV-1 from Klebsiella pneumoniae. However, the highest identity percentage (69 to 71%) was found with the plasmid-mediated β-lactamase TEM-1. PLA-1, which displayed very strong hydrolytic activity against penicillins, also displayed significant hydrolytic activity against cefepime and, to a lesser extent, against cefotaxime and aztreonam, but there was no hydrolytic activity against ceftazidime. Such a substrate profile suggests that the Raoultella β-lactamases PLA-1 and ORN-1 should be classified into the group 2be of the β-lactamase classification of K. Bush, G. A. Jacoby, and A. A. Medeiros (Antimicrob. Agents Chemother. 39:1211-1233, 1995). The highly homologous regions upstream of the bla PLA-1A and bla ORN-1A genes comprised a nucleotide sequence identical to the −35 region and another one very close to the −10 region of the bla LEN-1 gene. From now on, as the bla gene sequences of the most frequent Raoultella and Klebsiella species are available, the bla gene amplification method can be used to differentiate these species from each other, which the biochemical tests currently carried out in the clinical laboratory are unable to do.
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41

Fournier, B., P. H. Lagrange, and A. Philippon. "beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca." Antimicrobial Agents and Chemotherapy 40, no. 2 (February 1996): 460–63. http://dx.doi.org/10.1128/aac.40.2.460.

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beta-Lactamase gene promoters of 45 clinical Klebsiella oxytoca isolates resistant to beta-lactams and exhibiting beta-lactamase hyperproduction differed from those in 26 susceptible strains. Direct sequencing revealed one mutation in either the -10 or -35 conserved sequences: a G-to-A transition of the fifth base (67%) or a G-to-T transversion of the first base of the -10 sequence (27%) or a T-to-A transversion in the fourth base in the -35 sequence (4%). One strain carried both the -10 transition and the -35 transversion.
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42

Walsh, T. R., A. P. MacGowan, and P. M. Bennett. "Sequence analysis and enzyme kinetics of the L2 serine beta-lactamase from Stenotrophomonas maltophilia." Antimicrobial Agents and Chemotherapy 41, no. 7 (July 1997): 1460–64. http://dx.doi.org/10.1128/aac.41.7.1460.

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The L2 serine active-site beta-lactamase from Stenotrophomonas maltophilia has been classified as a clavulanic acid-sensitive cephalosporinase. The gene encoding this enzyme from S. maltophilia 1275 IID has been cloned on a 3.3-kb fragment into pK18 under the control of a Ptac promoter to generate recombinant plasmid pUB5840; when expressed in Escherichia coli, this gene confers resistance to cephalosporins and penicillins. Sequence analysis has revealed an open reading frame (ORF) of 909 bp with a GC content of 71.6%, comparable to that of the L1 metallo-beta-lactamase gene (68.4%) from the same bacterium. The ORF encodes an unmodified protein of 303 amino acids with a predicted molecular mass of 31.5 kDa, accommodating a putative leader peptide of 27 amino acids. Comparison of the amino acid sequence with those of other beta-lactamases showed it to be most closely related (54% identity) to the BLA-A beta-lactamase from Yersinia enterocolitica. Sequence identity is most obvious near the STXK active-site motif and the SDN loop motif common to all serine active-site penicillinases. Sequences outside the conserved regions display low homology with comparable regions of other class A penicillinases. Kinetics of the enzyme from the cloned gene demonstrated an increase in activity with cefotaxime but markedly less activity with imipenem than previously reported. Hence, the S. maltophilia L2 beta-lactamase is an inducible Ambler class A beta-lactamase which would account for the sensitivity to clavulanic acid.
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43

Martin, Juan F., Ruben Alvarez-Alvarez, and Paloma Liras. "Penicillin-Binding Proteins, β-Lactamases, and β-Lactamase Inhibitors in β-Lactam-Producing Actinobacteria: Self-Resistance Mechanisms." International Journal of Molecular Sciences 23, no. 10 (May 18, 2022): 5662. http://dx.doi.org/10.3390/ijms23105662.

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The human society faces a serious problem due to the widespread resistance to antibiotics in clinical practice. Most antibiotic biosynthesis gene clusters in actinobacteria contain genes for intrinsic self-resistance to the produced antibiotics, and it has been proposed that the antibiotic resistance genes in pathogenic bacteria originated in antibiotic-producing microorganisms. The model actinobacteria Streptomyces clavuligerus produces the β-lactam antibiotic cephamycin C, a class A β-lactamase, and the β lactamases inhibitor clavulanic acid, all of which are encoded in a gene supercluster; in addition, it synthesizes the β-lactamase inhibitory protein BLIP. The secreted clavulanic acid has a synergistic effect with the cephamycin produced by the same strain in the fight against competing microorganisms in its natural habitat. High levels of resistance to cephamycin/cephalosporin in actinobacteria are due to the presence (in their β-lactam clusters) of genes encoding PBPs which bind penicillins but not cephalosporins. We have revised the previously reported cephamycin C and clavulanic acid gene clusters and, in addition, we have searched for novel β-lactam gene clusters in protein databases. Notably, in S. clavuligerus and Nocardia lactamdurans, the β-lactamases are retained in the cell wall and do not affect the intracellular formation of isopenicillin N/penicillin N. The activity of the β-lactamase in S. clavuligerus may be modulated by the β-lactamase inhibitory protein BLIP at the cell-wall level. Analysis of the β-lactam cluster in actinobacteria suggests that these clusters have been moved by horizontal gene transfer between different actinobacteria and have culminated in S. clavuligerus with the organization of an elaborated set of genes designed for fine tuning of antibiotic resistance and cell wall remodeling for the survival of this Streptomyces species. This article is focused specifically on the enigmatic connection between β-lactam biosynthesis and β-lactam resistance mechanisms in the producer actinobacteria.
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44

Tamang, Migma Dorji, Hyang-Mi Nam, Geum-Chan Jang, Su-Ran Kim, Myung Hwa Chae, Suk-Chan Jung, Jae-Won Byun, Yong Ho Park, and Suk-Kyung Lim. "Molecular Characterization of Extended-Spectrum-β-Lactamase-Producing and Plasmid-Mediated AmpC β-Lactamase-Producing Escherichia coli Isolated from Stray Dogs in South Korea." Antimicrobial Agents and Chemotherapy 56, no. 5 (February 21, 2012): 2705–12. http://dx.doi.org/10.1128/aac.05598-11.

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ABSTRACTA total of 47 extended-spectrum-cephalosporin-resistantEscherichia colistrains isolated from stray dogs in 2006 and 2007 in the Republic of Korea were investigated using molecular methods. Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase phenotypes were identified in 12 and 23E. coliisolates, respectively. All 12 ESBL-producing isolates carriedblaCTX-Mgenes. The most common CTX-M types were CTX-M-14 (n= 5) and CTX-M-24 (n= 3). Isolates producing CTX-M-3, CTX-M-55, CTX-M-27, and CTX-M-65 were also identified. Twenty-one of 23 AmpC β-lactamase-producing isolates were found to carryblaCMY-2genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition toblaTEM-1, two isolates carriedblaDHA-1, and one of them cocarriedblaCMY-2. Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence ISEcp1upstream of theblagenes. Only in the case of CTX-M genes was there an IS903sequence downstream of the gene. The spread of ESBLs and AmpC β-lactamases occurred via both horizontal gene transfer, accounting for much of the CTX-M gene dissemination, and clonal spread, accounting for CMY-2 gene dissemination. The horizontal dissemination ofblaCTX-MandblaCMY-2genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread ofblaCMY-2was driven mainly byE. colistrains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report ofblaDHA-1inE. colistrains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producingE. coliisolates from dogs in the Republic of Korea.
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45

Naas, Thierry, Daniel Aubert, Ayla Özcan, and Patrice Nordmann. "Chromosome-Encoded Narrow-Spectrum Ambler Class A β-Lactamase GIL-1 from Citrobacter gillenii." Antimicrobial Agents and Chemotherapy 51, no. 4 (January 22, 2007): 1365–72. http://dx.doi.org/10.1128/aac.01152-06.

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ABSTRACT A novel β-lactamase gene was cloned from the whole-cell DNA of an enterobacterial Citrobacter gillenii reference strain that displayed a weak narrow-spectrum β-lactam-resistant phenotype and was expressed in Escherichia coli. It encoded a clavulanic acid-inhibited Ambler class A β-lactamase, GIL-1, with a pI value of 7.5 and a molecular mass of ca. 29 kDa. GIL-1 had the highest percent amino acid sequence identity with TEM-1 and SHV-1, 77%, and 67%, respectively, and only 46%, 31%, and 32% amino acid sequence identity with CKO-1 (C. koseri), CdiA1 (C. diversus), and SED-1 (C. sedlaki), respectively. The substrate profile of the purified GIL-1 was similar to that of β-lactamases TEM-1 and SHV-1. The bla GIL-1 gene was chromosomally located, as revealed by I-CeuI experiments, and was constitutively expressed at a low level in C. gillenii. No gene homologous to the regulatory ampR genes of chromosomal class C β-lactamases was found upstream of the bla GIL-1 gene, which fits the noninducibility of β-lactamase expression in C. gillenii. Rapid amplification of DNA 5′ ends analysis of the promoter region revealed putative promoter sequences that diverge from what has been identified as the consensus sequence in E. coli. The bla GIL-1 gene was part of a 5.5-kb DNA fragment bracketed by a 9-bp duplication and inserted between the d-lactate dehydrogenase gene and the ydbH genes; this DNA fragment was absent in other Citrobacter species. This work further illustrates the heterogeneity of β-lactamases in Citrobacter spp., which may indicate that the variability of Citrobacter species is greater than expected.
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46

Vila, J., M. Navia, J. Ruiz, and C. Casals. "Cloning and nucleotide sequence analysis of a gene encoding an OXA-derived beta-lactamase in Acinetobacter baumannii." Antimicrobial Agents and Chemotherapy 41, no. 12 (December 1997): 2757–59. http://dx.doi.org/10.1128/aac.41.12.2757.

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A clinical strain of Acinetobacter baumannii (strain Ab41) that was resistant to all beta-lactam antibiotics tested except ceftazidime, ceftriaxone, ceftizoxime, and imipenem produced three beta-lactamases: a presumptive chromosomal cephalosporinase, a TEM-1-like beta-lactamase (pI 5.4), and a novel OXA-derived beta-lactamase named OXA-21 (pI 7.0). The gene encoding OXA-21 was located in an integron. The nucleotide sequence showed three mutations compared with the sequence of OXA-3, with two being silent; the nonsilent mutation generated a substitution of Ile-217 to Met.
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47

Bootsma, H. J., H. van Dijk, J. Verhoef, A. Fleer, and F. R. Mooi. "Molecular characterization of the BRO beta-lactamase of Moraxella (Branhamella) catarrhalis." Antimicrobial Agents and Chemotherapy 40, no. 4 (April 1996): 966–72. http://dx.doi.org/10.1128/aac.40.4.966.

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A rapid increase in the prevalence of beta-lactamase-producing Moraxella (Branhamella) catarrhalis strains has been noticed during the last decades. Today, more than 80% of strains isolated worldwide produce beta-lactamase. To investigate beta-lactamase(s) of M. catarrhalis at the molecular level, the BRO-1 beta-lactamase gene (bla) was isolated as part of a 4,223-bp HindIII fragment. Sequence analysis indicated that bla encodes a polypeptide of 314 amino acid residues. Insertional inactivation of bla in M. catarrhalis resulted in complete abrogation of beta-lactamase production and ampicillin resistance, demonstrating that bla is solely responsible for beta-lactam resistance. Comparison with other beta-lactamases suggested that M. catarrhalis beta-lactamase is a unique enzyme with conserved residues at the active sites. The presence of a signal sequence for lipoproteins suggested that it is lipid modified at its N terminus. In keeping with this assumption was the observation that 10% of beta-lactamase activity was found in the membrane compartment of M. catarrhalis. M. catarrhalis strains produce two types of beta-lactamase, BRO-1 and BRO-2, which differ in their isoelectric points. The BRO-1 and BRO-2 genes from two ATCC strains of M. catarrhalis were sequenced, and only one amino acid difference was found between the predicted products. However, there was a 21-bp deletion in the promoter region of the BRO-2 gene, possibly explaining the lower level of production of BRO-2. The G + C content of bla (31%) was significantly lower than those of the flanking genes (47 and 50%), and the overall G + C content of the M. catarrhalis genome (41%). These results indicate that bla was acquired by horizontal gene transfer from another, still unknown species.
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48

Bradford, P. A., C. Urban, N. Mariano, S. J. Projan, J. J. Rahal, and K. Bush. "Imipenem resistance in Klebsiella pneumoniae is associated with the combination of ACT-1, a plasmid-mediated AmpC beta-lactamase, and the foss of an outer membrane protein." Antimicrobial Agents and Chemotherapy 41, no. 3 (March 1997): 563–69. http://dx.doi.org/10.1128/aac.41.3.563.

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Six Escherichia coli and 12 Klebsiella pneumoniae isolates from a single hospital expressed a common beta-lactamase with a pI of approximately 9.0 and were resistant to cefoxitin and cefotetan (MIC ranges, 64 to > 128 and 16 to > 128 micrograms/ml, respectively). Seventeen of the 18 strains produced multiple beta-lactamases. Most significantly, three K. pneumoniae strains were also resistant to imipenem (MICs, 8 to 32 micrograms/ml). Spectrophotometric beta-lactamase assays with purified enzyme indicated hydrolysis of cephamycins, in addition to cephaloridine and benzylpenicillin. The 4ene encoding the pI 9.0 beta-lactamase (designated ACT-1 for AmpC type) was cloned and sequenced, which revealed an ampC-type beta-lactamase gene that originated from Enterobacter cloacae and that had 86% sequence homology to the P99 beta-lactamase and 94% homology to the partial sequence of MIR-1. Southern blotting revealed that the gene encoding ACT-1 was on a large plasmid in some of the K. pneumoniae strains as well as on the chromosomes of all of the strains, suggesting that the gene is located on an easily mobilized element. Outer membrane protein profiles of the K. pneumoniae strains revealed that the three imipenem-resistant strains were lacking a major outer membrane protein of approximately 42 kDa which was present in the imipenem-susceptible strains. ACT-1 is the first plasmid-mediated AmpC-type beta-lactamase derived from Enterobacter which has been completely sequenced. This work demonstrates that in addition to resistance to cephamycins, imipenem resistance can occur in K. pneumoniae when a high level of the ACT-1 beta-lactamase is produced in combination with the loss of a major outer membrane protein.
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49

Chen, Yahua, Janice Succi, Fred C. Tenover, and Theresa M. Koehler. "β-Lactamase Genes of the Penicillin-Susceptible Bacillus anthracis Sterne Strain." Journal of Bacteriology 185, no. 3 (February 1, 2003): 823–30. http://dx.doi.org/10.1128/jb.185.3.823-830.2003.

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ABSTRACT Susceptibility to penicillin and other β-lactam-containing compounds is a common trait of Bacillus anthracis. β-lactam agents, particularly penicillin, have been used worldwide to treat anthrax in humans. Nonetheless, surveys of clinical and soil-derived strains reveal penicillin G resistance in 2 to 16% of isolates tested. Bacterial resistance to β-lactam agents is often mediated by production of one or more types of β-lactamases that hydrolyze the β-lactam ring, inactivating the antimicrobial agent. Here, we report the presence of two β-lactamase (bla) genes in the penicillin-susceptible Sterne strain of B. anthracis. We identified bla1 by functional cloning with Escherichia coli. bla1 is a 927-nucleotide (nt) gene predicted to encode a protein with 93.8% identity to the type I β-lactamase gene of Bacillus cereus. A second gene, bla2, was identified by searching the unfinished B. anthracis chromosome sequence database of The Institute for Genome Research for open reading frames (ORFs) predicted to encode β-lactamases. We found a partial ORF predicted to encode a protein with significant similarity to the carboxy-terminal end of the type II β-lactamase of B. cereus. DNA adjacent to the 5′ end of the partial ORF was cloned using inverse PCR. bla2 is a 768-nt gene predicted to encode a protein with 92% identity to the B. cereus type II enzyme. The bla1 and bla2 genes confer ampicillin resistance to E. coli and Bacillus subtilis when cloned individually in these species. The MICs of various antimicrobial agents for the E. coli clones indicate that the two β-lactamase genes confer different susceptibility profiles to E. coli; bla1 is a penicillinase, while bla2 appears to be a cephalosporinase. The β-galactosidase activities of B. cereus group species harboring bla promoter-lacZ transcriptional fusions indicate that bla1 is poorly transcribed in B. anthracis, B. cereus, and B. thuringiensis. The bla2 gene is strongly expressed in B. cereus and B. thuringiensis and weakly expressed in B. anthracis. Taken together, these data indicate that the bla1 and bla2 genes of the B. anthracis Sterne strain encode functional β-lactamases of different types, but gene expression is usually not sufficient to confer resistance to β-lactam agents.
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50

Galán, Juan-Carlos, María-Isabel Morosini, María-Rosario Baquero, Milagro Reig, and Fernando Baquero. "Haemophilus influenzae bla ROB-1 Mutations in Hypermutagenic ΔampC Escherichia coli Conferring Resistance to Cefotaxime and β-Lactamase Inhibitors and Increased Susceptibility to Cefaclor." Antimicrobial Agents and Chemotherapy 47, no. 8 (August 2003): 2551–57. http://dx.doi.org/10.1128/aac.47.8.2551-2557.2003.

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ABSTRACT The clinical use of cefaclor has been shown to enrich Haemophilus influenzae populations harboring cefaclor-hydrolyzing ROB-1 β-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or β-lactams plus β-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in H. influenzae. In order to establish which bla ROB-1 mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to β-lactamase inhibitors, a plasmid harboring bla ROB-1 was transformed into hypermutagenic strain Escherichia coli GB20 (ΔampC mutS::Tn10), and this construct was used in place of H. influenzae bla ROB-1. Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected β-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the bla ROB-1 gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169→Ser169 or the Arg164→Trp164 substitution or the double amino acid change Arg164→Trp164 and Ala237→Thr237. ROB-1 mutants that were resistant to β-lactams plus β-lactamase inhibitors and that harbored the Arg244→Cys244 or the Ser130→Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if bla ROB-1 mutants were selected by cefaclor, this drug would prevent the further evolution of this β-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or β-lactamase inhibitors.
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