Articles de revues : « Aminoglycosides uptake »

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Ford, D. M., R. H. Dahl, C. A. Lamp et B. A. Molitoris. « Apically and basolaterally internalized aminoglycosides colocalize in LLC-PK1 lysosomes and alter cell function ». American Journal of Physiology-Cell Physiology 266, n^o 1 (1 janvier 1994) : C52—C57. http://dx.doi.org/10.1152/ajpcell.1994.266.1.c52.

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Aminoglycosides bind to apical and basolateral (BL) membranes of renal epithelial cells. However, little is known regarding differential uptake and intracellular processing after internalization across these distinct surface membrane domains. To examine these processes independently, LLC-PK1 cells were grown on porous filters, which allow selective access to both domains. Apical and BL membrane uptakes of gentamicin (0.5 mM), quantified using [3H]gentamicin, were linear from 2 to 24 h (r = 0.99). The 4-h apical gentamicin uptake was 667 +/- 59 pmol/mg protein, the BL 748 +/- 26 pmol/mg protein, and concurrent apical and BL uptake 1,389 +/- 22 pmol/mg protein. Aminoglycoside uptake, documented using indirect immunogold techniques, occurred via the apical and BL endocytic systems and colocalized with cationic ferritin. Aminoglycosides internalized via the apical (gentamicin) and BL (tobramycin) membrane converged at the lysosomal level. Gentamicin incorporated via either domain significantly decreased lysosomal N-acetylglucosaminidase below control values (P < 0.05). We conclude that, after binding, aminoglycosides are internalized equally across apical and BL membranes of LLC-PK1 cells via receptor-mediated endocytosis, colocalize within the lysosomal compartment, and alter cellular function similarly.

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Rodriguez, Mônica B., et Sérgio O. P. Costa. « Spontaneous kanamycin-resistant Escherichia coli mutant with altered periplasmic oligopeptide permease protein (OppA) and impermeability to aminoglycosides ». Revista de Microbiologia 30, n^o 2 (avril 1999) : 153–56. http://dx.doi.org/10.1590/s0001-37141999000200013.

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A spontaneous kanamycin-resistant Escherichia coli mutant, showing cross resistance to five other aminoglycosides and absence of the OppA protein was isolated. [3H]-dihydrostreptomycin uptake is reduced in this mutant, implying that the oligopeptide transport system is involved in accumulation of aminoglycosides, although apparently not related with aminoglycoside permeability alteration due to bacterial adaptation to osmotic changes.

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McCollister, Bruce D., Matthew Hoffman, Maroof Husain et Andrés Vázquez-Torres. « Nitric Oxide Protects Bacteria from Aminoglycosides by Blocking the Energy-Dependent Phases of Drug Uptake ». Antimicrobial Agents and Chemotherapy 55, n^o 5 (22 février 2011) : 2189–96. http://dx.doi.org/10.1128/aac.01203-10.

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ABSTRACTOur investigations have identified a mechanism by which exogenous production of nitric oxide (NO) induces resistance of Gram-positive and -negative bacteria to aminoglycosides. An NO donor was found to protectSalmonellaspp. against structurally diverse classes of aminoglycosides of the 4,6-disubstituted 2-deoxystreptamine group. Likewise, NO generated enzymatically by inducible NO synthase of gamma interferon-primed macrophages protected intracellularSalmonellaagainst the cytotoxicity of gentamicin. NO levels that elicited protection against aminoglycosides repressedSalmonellarespiratory activity. NO nitrosylated terminal quinol cytochrome oxidases, without exerting long-lasting inhibition of NADH dehydrogenases of the electron transport chain. The NO-mediated repression of respiratory activity blocked both energy-dependent phases I and II of aminoglycoside uptake but not the initial electrostatic interaction of the drug with the bacterial cell envelope. As seen inSalmonella, the NO-dependent inhibition of the electron transport chain also afforded aminoglycoside resistance to the clinically important pathogensPseudomonas aeruginosaandStaphylococcus aureus. Together, these findings provide evidence for a model in which repression of aerobic respiration by NO fluxes associated with host inflammatory responses can reduce drug uptake, thus promoting resistance to several members of the aminoglycoside family in phylogenetically diverse bacteria.

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Ezraty, Benjamin, Alexandra Vergnes, Manuel Banzhaf, Yohann Duverger, Allison Huguenot, Ana Rita Brochado, Shu-Yi Su et al. « Fe-S Cluster Biosynthesis Controls Uptake of Aminoglycosides in a ROS-Less Death Pathway ». Science 340, n^o 6140 (27 juin 2013) : 1583–87. http://dx.doi.org/10.1126/science.1238328.

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All bactericidal antibiotics were recently proposed to kill by inducing reactive oxygen species (ROS) production, causing destabilization of iron-sulfur (Fe-S) clusters and generating Fenton chemistry. We find that the ROS response is dispensable upon treatment with bactericidal antibiotics. Furthermore, we demonstrate that Fe-S clusters are required for killing only by aminoglycosides. In contrast to cells, using the major Fe-S cluster biosynthesis machinery, ISC, cells using the alternative machinery, SUF, cannot efficiently mature respiratory complexes I and II, resulting in impendence of the proton motive force (PMF), which is required for bactericidal aminoglycoside uptake. Similarly, during iron limitation, cells become intrinsically resistant to aminoglycosides by switching from ISC to SUF and down-regulating both respiratory complexes. We conclude that Fe-S proteins promote aminoglycoside killing by enabling their uptake.

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Mao, Weimin, Mark S. Warren, Angela Lee, Anita Mistry et Olga Lomovskaya. « MexXY-OprM Efflux Pump Is Required for Antagonism of Aminoglycosides by Divalent Cations inPseudomonas aeruginosa ». Antimicrobial Agents and Chemotherapy 45, n^o 7 (1 juillet 2001) : 2001–7. http://dx.doi.org/10.1128/aac.45.7.2001-2007.2001.

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ABSTRACT Antagonism of aminoglycosides by divalent cations is well documented for Pseudomonas aeruginosa and is regarded as one of the problems in aminoglycoside therapy. It is generally considered that divalent cations interfere with uptake of aminoglycosides at both the outer and inner membranes. It has been demonstrated recently that aminoglycosides can be removed from cells ofP. aeruginosa by the three-component multidrug resistance efflux pump MexXY-OprM. We sought to investigate the interplay between efflux and uptake in resistance to aminoglycosides inP. aeruginosa. To do so, we studied the effects of the divalent cations Mg2+ and Ca2+ on susceptibility to aminoglycosides in a wild-type strain of P. aeruginosa and in mutants either overexpressing or lacking the MexXY-OprM efflux pump. MICs of gentamicin, streptomycin, amikacin, apramycin, netilmicin, and arbekacin were determined in Mueller-Hinton broth in the presence of cations added at concentrations that varied from 0.125 to 8 mM. We found, unexpectedly, that while both Mg2+ and Ca2+ antagonized aminoglycosides (up to a 64-fold decrease in susceptibility at 8 mM), antagonism was seen only in the strains of P. aeruginosa that contained the functional MexXY-OprM efflux pump. Our results indicate that inhibition of the MexXY-OprM efflux pump should abolish the antagonism of aminoglycosides by divalent cations, regardless of its precise mechanism. This may significantly increase the therapeutic index of aminoglycosides and improve the clinical utility of this important class of antibiotics.

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Kang, Hyung Sub, Dirk Kerstan, Long-jun Dai, Gordon Ritchie et Gary A. Quamme. « Aminoglycosides inhibit hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells ». Canadian Journal of Physiology and Pharmacology 78, n^o 8 (1 août 2000) : 595–602. http://dx.doi.org/10.1139/y00-038.

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The clinical use of aminoglycosides often leads to renal magnesium wasting and hypomagnesemia. Of the nephron segments, both the thick ascending limb of Henle's loop and the distal tubule play significant roles in renal magnesium conservation but the distal convoluted tubule exerts the final control of urinary excretion. An immortalized mouse distal convoluted tubule (MDCT) cell line has been extensively used to study the cellular mechanisms of magnesium transport in this nephron segment. Peptide hormones, such as parathyroid hormone (PTH), glucagon, calcitonin, and arginine vasopressin (AVP) stimulate Mg2+ uptake in MDCT cells that is modulated by extracellular polyvalent cations, Ca2+ and Mg2+. The present studies determined the effect of aminoglycosides on parathyroid hormone (PTH)-mediated cAMP formation and Mg2+ uptake in MDCT cells. Gentamicin, a prototypic aminoglycoside, illicited transient increases in intracellular Ca2+ from basal levels of 102 ± 13 nM to 713 ± 125 nM, suggesting a receptor-mediated response. In order to determine Mg2+ transport, MDCT cells were Mg2+-depleted by culturing in Mg2+-free media for 16 h and Mg2+ uptake was measured by microfluorescence after placing the depleted cells in 1.0 mM MgCl2. The mean rate of Mg2+ uptake, d([Mg2+]i)/dt, was 138 ± 24 nM/s in control MDCT cells. Gentamicin (50 µM) did not affect basal Mg2+ uptake (105 ± 29 nM/s), but inhibited PTH stimulated Mg2+ entry, decreasing it from 257 ± 36 nM/s to 108 ± 42 nM/s. This was associated with diminished PTH-stimulated cAMP formation, from 80 ± 2.5 to 23 ± 1 pmol/mg protein·5 min. Other aminoglycosides such as tobramycin, streptomycin, and neomycin also inhibited PTH-stimulated Mg2+ entry and cAMP formation. As these antibiotics are positively charged, the data suggest that aminoglycosides act through an extracellular polyvalent cation-sensing receptor present in distal convoluted tubule cells. We infer from these studies that aminoglycosides inhibit hormone-stimulated Mg2+ absorption in the distal convoluted tubule that may contribute to the renal magnesium wasting frequently observed with the clinical use of these antibiotics.Key words: intracellular Mg2+, Mg2+ uptake, aminoglycosides, gentamicin, tobramycin, streptomycin, neomycin, parathyroid hormone, microfluorescence, cAMP measurements.

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Jassem, Agatha N., James E. A. Zlosnik, Deborah A. Henry, Robert E. W. Hancock, Robert K. Ernst et David P. Speert. « In VitroSusceptibility of Burkholderia vietnamiensis to Aminoglycosides ». Antimicrobial Agents and Chemotherapy 55, n^o 5 (14 février 2011) : 2256–64. http://dx.doi.org/10.1128/aac.01434-10.

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ABSTRACTBurkholderia cepaciacomplex (BCC) bacteria are opportunistic pathogens that can cause severe disease in cystic fibrosis (CF) patients and other immunocompromised individuals and are typically multidrug resistant. Here we observed that unlike other BCC species, most environmental and clinicalBurkholderia vietnamiensisisolates were intrinsically susceptible to aminoglycosides but not to cationic antimicrobial peptides or polymyxin B. Furthermore, strains acquired aminoglycoside resistance during chronic CF infection, a phenomenon that could be induced under tobramycin or azithromycin pressurein vitro. In comparing susceptible and resistantB. vietnamiensisisolates, no gross differences in lipopolysaccharide structure were observed, all had lipid A-associated 4-amino-4-deoxy-l-arabinose residues, and all were resistant to the permeabilizing effects of aminoglycosides, a measure of drug entry via self-promoted uptake. However, susceptible isolates accumulated 5 to 6 times more gentamicin than a resistant isolate, and aminoglycoside susceptibility increased in the presence of an efflux pump inhibitor.B. vietnamiensisis therefore unusual among BCC bacteria in its susceptibility to aminoglycosides and capacity to acquire resistance. Aminoglycoside resistance appears to be due to decreased cellular accumulation as a result of active efflux.

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Hadidi, Kaivin, Ezequiel Wexselblatt, Jeffrey D. Esko et Yitzhak Tor. « Cellular uptake of modified aminoglycosides ». Journal of Antibiotics 71, n^o 1 (1 novembre 2017) : 142–45. http://dx.doi.org/10.1038/ja.2017.131.

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Jiang, Meiyan, Hongzhe Li, Anastasiya Johnson, Takatoshi Karasawa, Yuan Zhang, William B. Meier, Farshid Taghizadeh, Allan Kachelmeier et Peter S. Steyger. « Inflammation up-regulates cochlear expression of TRPV1 to potentiate drug-induced hearing loss ». Science Advances 5, n^o 7 (juillet 2019) : eaaw1836. http://dx.doi.org/10.1126/sciadv.aaw1836.

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Aminoglycoside antibiotics are essential for treating life-threatening bacterial infections, despite the risk of lifelong hearing loss. Infections induce inflammation and up-regulate expression of candidate aminoglycoside-permeant cation channels, including transient receptor potential vanilloid-1 (TRPV1). Heterologous expression of TRPV1 facilitated cellular uptake of (fluorescently tagged) gentamicin that was enhanced by agonists, and diminished by antagonists, of TRPV1. Cochlear TRPV1 was immunolocalized near the apical membranes of sensory hair cells, adjacent supporting cells, and marginal cells in the stria vascularis. Exposure to immunostimulatory lipopolysaccharides, to simulate of bacterial infections, increased cochlear expression of TRPV1 and hair cell uptake of gentamicin. Lipopolysaccharide exposure exacerbated aminoglycoside-induced auditory threshold shifts and loss of cochlear hair cells in wild-type, but not in heterozygous Trpv1+/− or Trpv1 knockout, mice. Thus, TRPV1 facilitates cochlear uptake of aminoglycosides, and bacteriogenic stimulation upregulates TRPV1 expression to exacerbate cochleotoxicity. Furthermore, loss-of-function polymorphisms in Trpv1 can protect against immunogenic exacerbation of aminoglycoside-induced cochleotoxicity.

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Schlessinger, D. « Failure of aminoglycoside antibiotics to kill anaerobic, low-pH, and resistant cultures. » Clinical Microbiology Reviews 1, n^o 1 (janvier 1988) : 54–59. http://dx.doi.org/10.1128/cmr.1.1.54.

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The critical inhibition of ribosome function by aminoglycosides has long been established. But the binding of drug to ribosomes is reversible: why then are aminoglycosides bactericidal? Several groups have shown that irreversible action (lethality) results from irreversible uptake into susceptible cells; conversely, resistance in cases such as anaerobiosis is associated with the failure of uptake. Oddly, the pattern of results excludes all traditional transport mechanisms; most unusual is the apparent dependence of uptake on the interaction of drug with ribosomes. A traditional view that ribosomes may function during uptake as a "sink" for aminoglycosides cannot explain all the data. Instead, the alternative is considered that cycling ribosomes at the cell membrane help to induce "one-way endocytic pores." Although no detailed mechanism is formulated, the results do suggest a way that the permeation of antibiotics might be systematically controllable to render them more cidal.

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El'Garch, Farid, Katy Jeannot, Didier Hocquet, Catherine Llanes-Barakat et Patrick Plésiat. « Cumulative Effects of Several Nonenzymatic Mechanisms on the Resistance of Pseudomonas aeruginosa to Aminoglycosides ». Antimicrobial Agents and Chemotherapy 51, n^o 3 (28 décembre 2006) : 1016–21. http://dx.doi.org/10.1128/aac.00704-06.

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ABSTRACT Screening of a Tn5-Hg insertional library (12,000 clones) constructed in wild-type Pseudomonas aeruginosa strain PAO1 identified four genes (namely, galU, nuoG, mexZ, and rplY) whose disruption individually led to increased resistance to aminoglycosides (means of twofold). Inactivation of these genes was associated with (i) impaired outer membrane uptake, (ii) reduced active transport, (iii) increased MexXY-OprM-mediated active efflux, and (iv) alteration of target of aminoglycosides, respectively. In addition, suppression of the gene rplY, which codes for ribosomal protein L25, was found to result in both moderate upregulation of the efflux system MexXY-OprM and hypersusceptibility to β-lactam antibiotics. Construction of double, triple, and quadruple mutants demonstrated cumulative effects of the different mechanisms on aminoglycoside resistance, with MICs increasing from 16- to 64-fold in the quadruple mutant compared to the wild-type strain PAO1. Altogether, these results illustrate how P. aeruginosa may gradually develop high resistance to these antibiotics via intrinsic (i.e., nonenzymatic) mechanisms, as in cystic fibrosis patients.

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Zemke, Anna C., Mark T. Gladwin et Jennifer M. Bomberger. « Sodium Nitrite Blocks the Activity of Aminoglycosides against Pseudomonas aeruginosa Biofilms ». Antimicrobial Agents and Chemotherapy 59, n^o 6 (23 mars 2015) : 3329–34. http://dx.doi.org/10.1128/aac.00546-15.

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ABSTRACTSodium nitrite has broad antimicrobial activity at pH 6.5, including the ability to prevent biofilm growth byPseudomonas aeruginosaon the surfaces of airway epithelial cells. Because of its antimicrobial activity, nitrite is being investigated as an inhaled agent for chronicP. aeruginosaairway infections in cystic fibrosis patients. However, the interaction between nitrite and commonly used aminoglycosides is unknown. This paper investigates the interaction between nitrite and tobramycin in liquid culture, abiotic biofilms, and a biotic biofilm model simulating the conditions in the cystic fibrosis airway. The addition of nitrite prevented killing by aminoglycosides in liquid culture, with dose dependence between 1.5 and 15 mM. The effect was not blocked by the nitric oxide scavenger CPTIO or dependent on efflux pump activity. Nitrite shifted the biofilm minimal bactericidal concentration (MBC-biofilm) from 256 μg/ml to >1,024 μg/ml in an abiotic biofilm model. In a biotic biofilm model, the addition of 50 mM nitrite decreased the antibiofilm activity of tobramycin by up to 1.2 log. Respiratory chain inhibition recapitulated the inhibition of aminoglycoside activity by nitrite, suggesting a potential mechanism of inhibition of energy-dependent aminoglycoside uptake. In summary, sodium nitrite induces resistance to both gentamicin and tobramycin inP. aeruginosagrown in liquid culture, as an abiotic biofilm, or as a biotic biofilm.

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Krahn, Thomas, Christie Gilmour, Justin Tilak, Sebastien Fraud, Nicholas Kerr, Calvin Ho-Fung Lau et Keith Poole. « Determinants of Intrinsic Aminoglycoside Resistance in Pseudomonas aeruginosa ». Antimicrobial Agents and Chemotherapy 56, n^o 11 (20 août 2012) : 5591–602. http://dx.doi.org/10.1128/aac.01446-12.

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ABSTRACTScreening of a transposon insertion mutant library ofPseudomonas aeruginosafor increased susceptibility to paromomycin identified a number of genes whose disruption enhanced susceptibility of this organism to multiple aminoglycosides, including tobramycin, amikacin, and gentamicin. These included genes associated with lipid biosynthesis or metabolism (lptA,faoA), phosphate uptake (pstB), and two-component regulators (amgRS, PA2797-PA2798) and a gene of unknown function (PA0392). Deletion mutants lacking these showed enhanced panaminoglycoside susceptibility that was reversed by the cloned genes, confirming their contribution to intrinsic panaminoglycoside resistance. None of these mutants showed increased aminoglycoside permeation of the cell envelope, indicating that increased susceptibility was not related to enhanced aminoglycoside uptake owing to a reduced envelope barrier function. Several mutants (pstB,faoA, PA0392,amgR) did, however, show increased cytoplasmic membrane depolarization relative to wild type following gentamicin exposure, consistent with the membranes of these mutants being more prone to perturbation, likely by gentamicin-generated mistranslated polypeptides. Mutants lacking any two of these resistance genes in various combinations invariably showed increased aminoglycoside susceptibility relative to single-deletion mutants, confirming their independent contribution to resistance and highlighting the complexity of the intrinsic aminoglycoside resistome inP. aeruginosa. Deletion of these genes also compromised the high-level panaminoglycoside resistance of clinical isolates, emphasizing their important contribution to acquired resistance.

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Luedtke, Nathan W., Peter Carmichael et Yitzhak Tor. « Cellular Uptake of Aminoglycosides, Guanidinoglycosides, and Poly-arginine ». Journal of the American Chemical Society 125, n^o 41 (octobre 2003) : 12374–75. http://dx.doi.org/10.1021/ja0360135.

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Chan, Gary L. C. « Alternative Dosing Strategy for Aminoglycosides : Impact on Efficacy, Nephrotoxicity, and Ototoxicity ». DICP 23, n^o 10 (octobre 1989) : 788–94. http://dx.doi.org/10.1177/106002808902301010.

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Accumulating evidence suggests that the therapeutic margin of aminoglycoside therapy may be improved by manipulation of dosing strategy. Recent understanding of concentration-dependent bactericidal activity and postantibiotic effect argues that the aminoglycosides may be administered in larger doses and at longer dosing intervals than currently recommended without compromising efficacy. Preliminary clinical experience suggests that once-daily regimens are as efficacious as conventional intermittent injections in the treatment of gram-negative infections including urinary tract infections, cystic fibrosis, and bacteremia in nonneutropenic patients. The transient, high peak serum concentrations achieved in once-daily dosing have not been associated with excessive nephrotoxicity or ototoxicity thus far. Decreased accumulation in renal cortex as a result of saturable renal uptake after the single daily dose may even reduce the incidence or severity of renal damage. Further studies on more patients are required to substantiate these preliminary findings.

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Girton, Richard A., David P. Sundin et Mark E. Rosenberg. « Clusterin protects renal tubular epithelial cells from gentamicin-mediated cytotoxicity ». American Journal of Physiology-Renal Physiology 282, n^o 4 (1 avril 2002) : F703—F709. http://dx.doi.org/10.1152/ajprenal.00060.2001.

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Clusterin is a heterodimeric secreted glycoprotein that is upregulated after acute renal injury. In aminoglycoside nephrotoxicity, clusterin is induced in the tubular epithelium and increased levels are found in the urine. In this study, we developed an in vitro model of gentamicin-induced cytotoxicity in renal proximal tubule cells and tested whether clusterin protected these cells from injury. LLC-PK1 cells were incubated with varying concentrations of gentamicin in serum-free media, and cytotoxicity was quantified by lactate dehydrogenase release and confirmed by vital dye exclusion. A dose-dependent increase in cytotoxicity occurred with gentamicin concentrations up to 27 mg/ml. Clusterin decreased cytotoxicity in a dose- and time-dependent manner at 6, 12, and 24 h, whereas albumin, used as a control protein, had no effect. In contrast to the aminoglycoside model, when cells were injured by depletion of ATP, clusterin had only a minimally protective effect. LLC-PK1 cells did not express megalin, a receptor that can mediate the uptake of both clusterin and aminoglycosides into proximal tubule cells. Uptake of gentamicin into LLC-PK1cells was observed despite the absence of megalin. In conclusion, clusterin specifically protects against gentamicin-induced renal tubular cell injury by a megalin-independent mechanism.

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Reena Rajan. « Mechanism of Drug Resistance in Enterococci and Therapeutic Options - A Review ». International Journal of Research in Pharmaceutical Sciences 12, n^o 1 (6 janvier 2021) : 102–6. http://dx.doi.org/10.26452/ijrps.v12i1.3942.

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Enterococci exhibit an array of ways for constitutional and extrinsic resistance to primary antimicrobial agents available for clinical use. Susceptibility of these agents to β lactams, aminoglycosides or glycopeptides antibiotics or low susceptibility to combination of these agents, monomicrobial or polymicrobial nature of the infection, the involvement of heart valves or other endovascular structures affects therapy of Enterococcal infection. Vancomycin-resistant phenotypes A and B are most prevalent among medically important Enterococci isolates. Due to poor uptake of aminoglycosides, moderate level inherent resistance was reported in Enterococci. Gentamicin and Streptomycin are among the aminoglycoside antibiotics recommended for synergistic combination therapy with a cell wall acting agent. Enterococci isolates display inherent resistance to beta-lactam antibiotics due to less affinity penicillin-binding proteins, class B. Resistance to macrolides, due to erm B genotype and efflux proteins are common in Enterococci. Fluoroquinolone resistance due to genetic changes in chromosomal resistance determining regions has been observed in Enterococci isolates. Despite studies on good invitro action of Daptomycin, Linezolid and Tigecycline on Enterococci, their use may be limited due to shortage of clinical data and emergence of drug resistance. Thus optimal therapeutic option for Multidrug-resistant Enterococci infection is based on empirical observation, higher doses and combination therapies. This article reviews the antimicrobial resistance mechanism in Enterococci and available therapeutic options.

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Elkins, Christopher A., et Lisa B. Mullis. « Bile-Mediated Aminoglycoside Sensitivity in Lactobacillus Species Likely Results from Increased Membrane Permeability Attributable to Cholic Acid ». Applied and Environmental Microbiology 70, n^o 12 (décembre 2004) : 7200–7209. http://dx.doi.org/10.1128/aem.70.12.7200-7209.2004.

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ABSTRACT Few studies have been conducted on antimicrobial resistance in lactobacilli, presumably because of their nonpathogenic nature as anaerobic commensals. We assessed resistance in 43 type strains and isolates representing 14 species by using agar disk diffusion and MIC analysis in MRS medium. Most noteworthy were two general phenotypes displayed by nearly every strain tested: (i) they were more susceptible (up to 256-fold in some cases) to the deconjugated bile acid cholic acid than to the conjugate taurocholic or taurodeoxycholic acid, and (ii) they became susceptible to aminoglycosides when assayed on agar medium containing 0.5% fractionated bovine bile (ox gall). Two-dimensional MIC analyses of one representative strain, Lactobacillus plantarum WCFS1, at increasing concentrations of ox gall (0 to 30.3 mg/ml) displayed corresponding decreases in resistance to all of the aminoglycosides tested and ethidium bromide. This effect was clinically relevant, with the gentamicin MIC decreasing from >1,000 to 4 μg/ml in just 3.8 mg of ox gall per ml. In uptake studies at pH 6.5, [G-3H]gentamicin accumulation increased over control levels when cells of this strain were exposed to bile acids or reserpine but not when they were exposed to carbonyl cyanide m-chlorophenylhydrazone. The effect was dramatic, particularly with cholic acid, increasing up to 18-fold, whereas only modest increases, 3- and 5-fold, could be achieved with taurocholic acid and ox gall, respectively. Since L. plantarum, particularly strain WCFS1, is known to encode bile salt hydrolase (deconjugation) activity, our data indicate that mainly cholic acid, but not taurocholic acid, effectively permeabilizes the membrane to aminoglycosides. However, at pHs approaching neutral conditions in the intestinal lumen, aminoglycoside resistance due to membrane impermeability may be complemented by a potential efflux mechanism.

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Sandoval, Ruben M., Robert L. Bacallao, Kenneth W. Dunn, Jeffrey D. Leiser et Bruce A. Molitoris. « Nucleotide depletion increases trafficking of gentamicin to the Golgi complex in LLC-PK1 cells ». American Journal of Physiology-Renal Physiology 283, n^o 6 (1 décembre 2002) : F1422—F1429. http://dx.doi.org/10.1152/ajprenal.00095.2002.

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Having shown rapid trafficking of aminoglycosides to the Golgi complex in cell culture, we focused on the injurious interaction that occurs when gentamicin administration is preceded by renal ischemia. Using Texas red-labeled gentamicin as a tracer, we determined that 15 min of cellular nucleotide depletion did not significantly increase subsequent uptake. However, cells previously depleted of nucleotides accumulated significantly more Texas red-labeled gentamicin within a dispersed Golgi complex. Using Ricinus communis and Lens culinaris lectins, which label specific compartments of the Golgi complex ( trans-Golgi network/ trans and medial/ cis compartments, respectively), we determined that the medial/ cis compartment dispersed after 15 min of nucleotide depletion but the trans-Golgi network/ trans compartment remained unaffected. An increase in the number of cells exhibiting disrupted medial/ cis-Golgi morphology after repletion in physiological media containing gentamicin was also seen. In summary, the increase in nephrotoxicity seen when ischemia precedes aminoglycoside uptake may be part of a complex mechanism initially involving increased Golgi accumulation and prolonged Golgi dispersion. The Golgi complex must then endure the effects of gentamicin accumulated in larger quantities in an aberrant physiological state.

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Lindgren, Helena, et Anders Sjöstedt. « Gallium Potentiates the Antibacterial Effect of Gentamicin against Francisella tularensis ». Antimicrobial Agents and Chemotherapy 60, n^o 1 (26 octobre 2015) : 288–95. http://dx.doi.org/10.1128/aac.01240-15.

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ABSTRACTThe reasons why aminoglycosides are bactericidal have not been not fully elucidated, and evidence indicates that the cidal effects are at least partly dependent on iron. We demonstrate that availability of iron markedly affects the susceptibility of the facultative intracellular bacteriumFrancisella tularensisstrain SCHU S4 to the aminoglycoside gentamicin. Specifically, the intracellular depots of iron were inversely correlated to gentamicin susceptibility, whereas the extracellular iron concentrations were directly correlated to the susceptibility. Further proof of the intimate link between iron availability and antibiotic susceptibility were the findings that a ΔfslAmutant, which is defective for siderophore-dependent uptake of ferric iron, showed enhanced gentamicin susceptibility and that a ΔfeoBmutant, which is defective for uptake of ferrous iron, displayed complete growth arrest in the presence of gentamicin. Based on the aforementioned findings, it was hypothesized that gallium could potentiate the effect of gentamicin, since gallium is sequestered by iron uptake systems. The ferrozine assay demonstrated that the presence of gallium inhibited >70% of the iron uptake. Addition of gentamicin and/or gallium to infected bone marrow-derived macrophages showed that both 100 μM gallium and 10 μg/ml of gentamicin inhibited intracellular growth of SCHU S4 and that the combined treatment acted synergistically. Moreover, treatment ofF. tularensis-infected mice with gentamicin and gallium showed an additive effect. Collectively, the data demonstrate that SCHU S4 is dependent on iron to minimize the effects of gentamicin and that gallium, by inhibiting the iron uptake, potentiates the bactericidal effect of gentamicinin vitroandin vivo.

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Acosta, Iván Camilo, Leonardo Posada, Mónica Gabriela Huertas et María Mercedes Zambrano Eder. « The effect of aminoglycosides on horizontal gene transfer in Klebsiella pneumoniae ». Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales 44, n^o 170 (16 mars 2020) : 105–20. http://dx.doi.org/10.18257/raccefyn.985.

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Antibiotic-resistant bacteria represent a global risk to public health. Horizontal gene transfer, a common mechanism for genetic exchange in bacteria, plays an essential role in the acquisition of resistance genes. In this work, we evaluated the effect of sub-lethal concentrations of antibiotics on plasmid transfer by conjugation and transformation in the opportunistic pathogen Klebsiella pneumoniae. Despite not being naturally competent, this bacterium could acquire extracellular DNA from various plasmids at a very low frequency, which increased upon incubating cells with the aminoglycoside antibiotics amikacin and gentamicin. Transfer by conjugation analyzed using a clinical isolate carrying plasmid pNDM-1 also increased in the presence of sub-lethal concentrations of antibiotics. An RNAseq analysis showed differential expression of several genes when cells were incubated in the presence of sub-lethal concentrations of amikacin suggesting metabolic and regulatory changes, as well as alteration of cell envelope components that could affect the uptake of foreign DNA. These results suggest that sub-lethal concentrations of some aminoglycosides, in particular amikacin, can promote the transfer of resistance-bearing genetic elements in K. pneumoniae, which is relevant for understanding the spread of resistance determinants in this human pathogen.

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Jiang, Meiyan, Qi Wang, Takatoshi Karasawa, Ja-Won Koo, Hongzhe Li et Peter S. Steyger. « Sodium-Glucose Transporter-2 (SGLT2 ; SLC5A2) Enhances Cellular Uptake of Aminoglycosides ». PLoS ONE 9, n^o 9 (30 septembre 2014) : e108941. http://dx.doi.org/10.1371/journal.pone.0108941.

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Andrade, Jacqueline C., Maria Flaviana B. Morais Braga, Gláucia Morgana M. Guedes, Saulo R. Tintino, Maria A. Freitas, Lucindo J. Quintans, Jr., Irwin R. A. Menezes et Henrique D. M. Coutinho. « Cholecalciferol, Ergosterol, and Cholesterol Enhance the Antibiotic Activity of Drugs ». International Journal for Vitamin and Nutrition Research 88, n^o 5-6 (1 décembre 2018) : 244–50. http://dx.doi.org/10.1024/0300-9831/a000268.

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Abstract. Background: This is the first report demonstrating the antibiotic-modifying activity of cholecalciferol. Aim: In this study, cholecalciferol was evaluated against multiresistant strains of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Methods: The antibacterial and modulatory effects of cholecalciferol, ergosterol, and cholesterol (8–512 μg/mL) were evaluated by microdilution assay against multiresistant bacterial strains. Results: Cholecalciferol, when combined with aminoglycosides, was more effective against P. aeruginosa, reducing the concentration of amikacin and gentamicin necessary to inhibit bacterial growth from 156.25 to 39.06 μg/mL and from 39.06 to 9.76 μg/mL, respectively. It is possible that cholecalciferol, due to its lipid-soluble nature, had a lipophilic interaction with the cell membrane, enhancing antibiotic uptake. Cholesterol and ergosterol were used to see if the mechanism of action of cholecalciferol was similar to that of these lipid compounds. Ergosterol and cholesterol increased aminoglycoside activity, where the effect was greater with higher subinhibitory concentration of sterol. Conclusions: There is no reported study on the use of cholesterol and ergosterol as modulators of antibiotics or any other drug, making this the first study in this area highlighting the interaction between cholesterol, ergosterol, and cholecalciferol with regard to modifying aminoglycoside activity.

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McKay, Susannah L., et Daniel A. Portnoy. « Ribosome Hibernation Facilitates Tolerance of Stationary-Phase Bacteria to Aminoglycosides ». Antimicrobial Agents and Chemotherapy 59, n^o 11 (31 août 2015) : 6992–99. http://dx.doi.org/10.1128/aac.01532-15.

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ABSTRACTUpon entry into stationary phase, bacteria dimerize 70S ribosomes into translationally inactive 100S particles by a process called ribosome hibernation. Previously, we reported that the hibernation-promoting factor (HPF) ofListeria monocytogenesis required for 100S particle formation and facilitates adaptation to a number of stresses. Here, we demonstrate that HPF is required for the high tolerance of stationary-phase cultures to aminoglycosides but not to beta-lactam or quinolone antibiotics. The sensitivity of a Δhpfmutant to gentamicin was suppressed by the bacteriostatic antibiotics chloramphenicol and rifampin, which inhibit translation and transcription, respectively. Disruption of the proton motive force by the ionophore carbonyl cyanidem-chlorophenylhydrazone or mutation of genes involved in respiration also suppressed the sensitivity of the Δhpfmutant. Accordingly, Δhpfmutants had aberrantly high levels of ATP and reducing equivalents during prolonged stationary phase. Analysis of bacterial uptake of fluorescently labeled gentamicin demonstrated that the Δhpfmutant harbored increased intracellular levels of the drug. Finally, deletion of the main ribosome hibernation factor ofEscherichia coli, ribosome modulation factor (rmf), rendered these bacteria susceptible to gentamicin. Taken together, these data suggest that HPF-mediated ribosome hibernation results in repression of the metabolic activity that underlies aminoglycoside tolerance. HPF is conserved in nearly every bacterial pathogen, and the role of ribosome hibernation in antibiotic tolerance may have clinical implications.

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Ahmed, Maizbha Uddin, Jian Li et Qi (Tony) Zhou. « Tobramycin Reduces Pulmonary Toxicity of Polymyxin B via Inhibiting the Megalin-Mediated Drug Uptake in the Human Lung Epithelial Cells ». Pharmaceutics 16, n^o 3 (12 mars 2024) : 389. http://dx.doi.org/10.3390/pharmaceutics16030389.

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Accumulation of polymyxins in the lung epithelial cells can lead to increased mitochondrial oxidative stress and pulmonary toxicity. Aminoglycosides and polymyxins are used, via intravenous and pulmonary delivery, against multidrug-resistant Gram-negative pathogens. Our recent in vitro and animal studies demonstrated that the co-administration of polymyxins with aminoglycosides decreases polymyxin-induced pulmonary toxicity. The aim of this study was to investigate the in vitro transport and uptake of polymyxin B and tobramycin in human lung epithelial Calu-3 cells and the mechanism of reduced pulmonary toxicity resulting from this combination. Transport, intracellular localization, and accumulation of polymyxin B and tobramycin were investigated using doses of 30 mg/L polymyxin B, 70 mg/L tobramycin, and the combination of both. Adding tobramycin significantly (p < 0.05) decreased the polymyxin B-induced cytotoxicity in Calu-3 cells. The combination treatment significantly reduced the transport and uptake of polymyxin B and tobramycin in Calu-3 cells, compared to each drug alone, which supported the reduced pulmonary toxicity. We hypothesized that cellular uptake of polymyxin B and tobramycin shared a common transporter, megalin. We further investigated the megalin expression of Calu-3 cells using confocal microscopy and evaluated megalin activity using a megalin substrate, FITC-BSA, and a megalin inhibitor, sodium maleate. Both polymyxin B and tobramycin significantly inhibited FITC-BSA uptake by Calu-3 cells in a concentration-dependent manner. Sodium maleate substantially inhibited polymyxin B and tobramycin transport and cellular accumulation in the Calu-3 cell monolayer. Our study demonstrated that the significantly reduced uptake of polymyxin B and tobramycin in Calu-3 cells is attributed to the mechanism of action that determines that polymyxin B and tobramycin share a common transporter, megalin.

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Lopes, Luma Clarindo, Muhammad Hayat et Sabine Kuss. « Electrochemical Detection of Tobramycin Resistance in Pseudomonas Aeruginosa ». ECS Meeting Abstracts MA2022-01, n^o 43 (7 juillet 2022) : 1858. http://dx.doi.org/10.1149/ma2022-01431858mtgabs.

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Pseudomonas aeruginosa are Gram-negative anaerobic bacteria and is listedby the World Health Organization as one of the critical antibiotic-resistant pathogens1. The treatment for P. aeruginosa infection can be challenging, since this pathogen often exhibits an enhanced resistance to antibiotics, including aminoglycosides, such as Tobramycin (TOB). These are called mucoid strains and are mainly found in the lungs of cystic fibrosis patients, where it is a common cause of death for these individuals2. The overall goal of the presented work is the development of an electrochemical method capable of detecting TOB uptake in P. aeruginosa. Drug susceptible and drug resistant strains of P. aeruginosa were exposed to a TOB solution for different time intervals (Figure 1). By removing organisms from the solution after incubation, the remaining TOB in solution can be determined by electrochemistry. Resistant bacteria strains showed significantly lower TOB uptake than susceptible organisms, because cellular drug resistant mechanisms enable them to inhibit TOB absorption. The presented drug uptake studies demonstrate the sensitivity of electrochemistry to detect drug resistance in living bacteria. References Singh, M., Yau, Y. C. W., Wang, S., Waters, V. & Kumar, A. MexXY efflux pump overexpression and aminoglycoside resistance in cystic fibrosis isolates of pseudomonas aeruginosa from chronic infections. Canadian Journal of Microbiology 63, 929–938 (2017). Germoni, L. A. P., Bremer, P. J. & Lamont, I. L. The effect of alginate lyase on the gentamicin resistance of Pseudomonas aeruginosa in mucoid biofilms. Journal of Applied Microbiology 121, 126–135 (2016). Figure 1

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Mironov, Alexander, Tatyana Seregina, Konstantin Shatalin, Maxim Nagornykh, Rustem Shakulov et Evgeny Nudler. « CydDC functions as a cytoplasmic cystine reductase to sensitizeEscherichia colito oxidative stress and aminoglycosides ». Proceedings of the National Academy of Sciences 117, n^o 38 (8 septembre 2020) : 23565–70. http://dx.doi.org/10.1073/pnas.2007817117.

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l-cysteine is the source of all bacterial sulfurous biomolecules. However, the cytoplasmic level ofl-cysteine must be tightly regulated due to its propensity to reduce iron and drive damaging Fenton chemistry. It has been proposed that inEscherichia colithe component of cytochromebd-I terminal oxidase, the CydDC complex, shuttles excessivel-cysteine from the cytoplasm to the periplasm, thereby maintaining redox homeostasis. Here, we provide evidence for an alternative function of CydDC by demonstrating that thecydDphenotype, unlike that of the bona fidel-cysteine exportereamA, parallels that of thel-cystine importertcyP.Chromosomal induction ofeamA, but not ofcydDC, from a strong pLtetO-1 promoter (Ptet) leads to the increased level of extracellularl-cysteine, whereas induction ofcydDCortcyPcauses the accumulation of cytoplasmicl-cysteine. Congruently, inactivation ofcydDrenders cells resistant to hydrogen peroxide and to aminoglycoside antibiotics. In contrast, induction ofcydDCsensitizes cells to oxidative stress and aminoglycosides, which can be suppressed byeamAoverexpression. Furthermore, inactivation of the ferric uptake regulator (fur)in Ptet-cydDCor Ptet-tcyPcells results in dramatic loss of survival, whereas catalase (katG) overexpression suppresses the hypersensitivity of both strains to H2O2. These results establish CydDC as a reducer of cytoplasmic cystine, as opposed to anl-cysteine exporter, and further elucidate a link between oxidative stress, antibiotic resistance, and sulfur metabolism.

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Decorti, Giuliana, Luigi Candussio, Fiora Bartoli Klugmann et Luciano Baldini. « Effect of Neomycin and Other Aminoglycosides on Adriamycin Uptake in Rat Peritoneal Mast Cells ». Pharmacology & ; Toxicology 73, n^o 6 (décembre 1993) : 341–43. http://dx.doi.org/10.1111/j.1600-0773.1993.tb01362.x.

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Li, Hongzhe, Yongchuan Chai et Liana Sargsyan. « Otitis media-induced cochlear immune response and opportunistic ototoxicity ». Journal of the Acoustical Society of America 151, n^o 4 (avril 2022) : A147. http://dx.doi.org/10.1121/10.0010925.

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Lipopolysaccharide (LPS), an essential component of the bacterial endotoxin, activates tissue macrophages and triggers the release of inflammatory cytokines. In animal models, intratympanic ( i.t.) injection of LPS is known to simulate acute otitis media (AOM) and modifies the structure and function of the inner ear. However, whether LPS-induced AOM modulates the uptake of ototoxic aminoglycosides in vivo is unclear. Here, we established an AOM mouse model to investigate the gentamicin uptake in the inner ear and the change of cochlear inflammation for pertaining ototoxicity mechanisms. We found that LPS-induced AOM switched on the cochlear inflammatory response, including macrophage infiltration and upregulation of pro-inflammation cytokines, and significantly enhanced the cochlear uptake of gentamicin. Potential mechanisms of enhanced drug uptake may include increased strial permeability due to acute middle-ear inflammation, resulting in higher drug concentration in the stria vascularis and the endolymph, and subsequently higher drug uptake by hair cells. Other possible mechanisms, such as the activation of specific candidate channels and endocytosis followed by inflammation, need to be further interrogated. In sum, this study improves our understanding of drug trafficking in the pathological cochlea and provides a reference for drug treatment of AOM while protecting the inner ear function.

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Lui, Eric Chi-Chung, et Reina Bendayan. « Gentamicin uptake by LLCPK1 cells : effect of intracellular and extracellular pH changes ». Canadian Journal of Physiology and Pharmacology 76, n^o 2 (1 février 1998) : 155–60. http://dx.doi.org/10.1139/y98-008.

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The mechanisms by which aminoglycosides are transported across the luminal membrane of renal proximal tubular cells remain unclear. A luminal organic cation/H+ exchange as well as an adsorptive endocytosis membrane process has been proposed to be involved in gentamicin renal accumulation. The objectives of this work were to explore further the effects of intracellular and extracellular pH changes on gentamicin uptake. [3H]Gentamicin uptake by a continuous renal epithelial cell line, LLCPK1, grown as a monolayer on an impermeable surface was measured at different temperatures and pH conditions and in the presence of various inhibitors. Uptake of gentamicin was found to be carrier mediated (Km = 1.26 ± 0.22 mM, Vmax = 289 ± 27 pmol ·mg-1 ·min-1), energy dependent (inhibited in part by sodium azide), and temperature dependent (37°C > 4°C). Fifteen-minute gentamicin (10 µM) uptake was inhibited by 1 mM of the organic cations cimetidine (61.0%), quinidine (73.5%), quinine (68.6%), and verapamil (61.5%). More importantly, while an outwardly directed proton gradient did not have a significant effect on gentamicin uptake, extracellular acidification (pH 6.5), which leads to a higher degree of gentamicin ionization, significantly enhanced gentamicin uptake by LLCPK1 monolayer cells. These results suggest that the luminal organic cation/H+ exchanger is not involved in gentamicin uptake by renal cultured epithelial cells. Rather, the cationic charge of gentamicin appears to be one of the primary determinants for renal luminal uptake.Key words: gentamicin, LLCPK1 cells, pH, nephrotoxicity.

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Kang, Hyung Sub, Dirk Kerstan, Long-jun Dai, Gordon Ritchie et Gary A. Quamme. « Aminoglycosides inhibit hormone-stimulated Mg²⁺ uptake in mouse distal convoluted tubule cells ». Canadian Journal of Physiology and Pharmacology 78, n^o 8 (2000) : 595–602. http://dx.doi.org/10.1139/cjpp-78-8-595.

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Deng, Wanyan, Tiwei Fu, Zhen Zhang, Xiao Jiang, Jianping Xie, Hang Sun, Peng Hu et al. « L-lysine potentiates aminoglycosides against Acinetobacter baumannii via regulation of proton motive force and antibiotics uptake ». Emerging Microbes & ; Infections 9, n^o 1 (1 janvier 2020) : 639–50. http://dx.doi.org/10.1080/22221751.2020.1740611.

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Aslangul, Elisabeth, Laurent Massias, Alain Meulemans, Françoise Chau, Antoine Andremont, Patrice Courvalin, Bruno Fantin et Raymond Ruimy. « Acquired Gentamicin Resistance by Permeability Impairment in Enterococcus faecalis ». Antimicrobial Agents and Chemotherapy 50, n^o 11 (novembre 2006) : 3615–21. http://dx.doi.org/10.1128/aac.00390-06.

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ABSTRACT Enterococci are intrinsically resistant to low levels of aminoglycosides. We previously selected in vitro and in vivo Enterococcus faecalis with intermediate-level resistance to gentamicin that did not abolish synergism with a cell-wall-active agent (E. Aslangul et al., Antimicrob. Agents Chemother. 49:4144-4148, 2005). The aim of this study was to investigate the mechanism of resistance to gentamicin in the 1688-G3 third-step mutant (MIC, 512 μg/ml) of E. faecalis JH2-2. No mutations were found in the genes for L6 ribosomal protein and the four copies of 16S rRNA. Production of a known aminoglycoside-modifying enzyme was unlikely due to the distinct resistance phenotype and absence of the corresponding genes. Efflux was also unlikely since ethidium bromide MICs were similar for JH2-2 and 1688-G3 and since the pump inhibitors reserpine and verapamil had no effect on gentamicin resistance in both strains. To study gentamicin accumulation, we developed a nonisotopic method based on a fluorescent polarization immunoassay. Impaired gentamicin accumulation was observed in 1688-G3 compared to JH2-2 and was only partially reversible by the N,N′-dicyclohexylcarbodiimide (DCCD) uncoupler agent. The lower sensitivity of 1688-G3 to DCCD suggested alteration of the FoF1-ATPase. However, no mutations were detected in the structural genes (atp) for the Fo channel and no difference in transcript levels of atpB and atpE was found between 1688-G3 and JH2-2. Our data are compatible with acquisition of intermediate-level gentamicin resistance by uptake impairment in E. faecalis.

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Kocúreková, Tímea, Lívia Karahutová et Dobroslava Bujňáková. « Antimicrobial Susceptibility and Detection of Virulence-Associated Genes in Escherichia coli Strains Isolated from Commercial Broilers ». Antibiotics 10, n^o 11 (26 octobre 2021) : 1303. http://dx.doi.org/10.3390/antibiotics10111303.

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The aim of this study was to investigate the presence of iron-uptake and virulence genes, antibiotic resistance profiles, and phylogenetic relatedness in 115 Escherichia coli (E. coli) strains isolated from broilers in Slovakia and to determine their potential threat to human health. The most frequent phylogroups were B1 (37%) and A (21%), and 33.9% strains were included in pathogenic groups. The commonly observed iron-uptake genes were feoB (94%), sitA (83%), and iutA (58%). Protectins (iss, kpsMTII) were identified in 30% of samples. Four percent of B2-associated broilers carried the papC (P fimbria) gene connected with upper urinary tract infection. The dominant resistance was to tetracycline (49%), ampicillin (66%), ampicillin + sulbactam (27%), ciprofloxacin (61%), and trimethoprim + sulfonamide (34%); moreover, sporadically occurring resistance to cephalosporins, aminoglycosides, fluoroquinolones, and polypeptide colistin was observed. Genotypic analysis of resistance revealed the presence of blaCTX-M-1 and blaCTX-M-2 in two isolates from broilers. Commercial broilers can be reservoirs of virulent and resistant genes as well as E. coli causing (extra-)intestinal infections, which can be a potential threat to humans via direct contact and food.

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Takahashi, Masayuki, Yukihiko Aramaki, Asaichi Inaba et Seishi Tsuchiya. « Inhibition of alkaline phosphatase activity and d-glucose uptake in rat renal brush-border membrane vesicles by aminoglycosides ». Biochimica et Biophysica Acta (BBA) - Biomembranes 903, n^o 1 (septembre 1987) : 31–36. http://dx.doi.org/10.1016/0005-2736(87)90152-0.

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Leyton, Benjamin, Juliana Nunes Ramos, Paulo Victor Pereira Baio, João Flávio Carneiro Veras, Cassius Souza, Andreas Burkovski, Ana Luíza Mattos-Guaraldi, Verônica Viana Vieira et Michel Abanto Marin. « Treat Me Well or Will Resist : Uptake of Mobile Genetic Elements Determine the Resistome of Corynebacterium striatum ». International Journal of Molecular Sciences 22, n^o 14 (13 juillet 2021) : 7499. http://dx.doi.org/10.3390/ijms22147499.

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Corynebacterium striatum, a bacterium that is part of the normal skin microbiota, is also an opportunistic pathogen. In recent years, reports of infections and in-hospital and nosocomial outbreaks caused by antimicrobial multidrug-resistant C. striatum strains have been increasing worldwide. However, there are no studies about the genomic determinants related to antimicrobial resistance in C. striatum. This review updates global information related to antimicrobial resistance found in C. striatum and highlights the essential genomic aspects in its persistence and dissemination. The resistome of C. striatum comprises chromosomal and acquired elements. Resistance to fluoroquinolones and daptomycin are due to mutations in chromosomal genes. Conversely, resistance to macrolides, tetracyclines, phenicols, beta-lactams, and aminoglycosides are associated with mobile genomic elements such as plasmids and transposons. The presence and diversity of insertion sequences suggest an essential role in the expression of antimicrobial resistance genes (ARGs) in genomic rearrangements and their potential to transfer these elements to other pathogens. The present study underlines that the resistome of C. striatum is dynamic; it is in evident expansion and could be acting as a reservoir for ARGs.

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Kwon, Dong H., et Chung-Dar Lu. « Polyamines Induce Resistance to Cationic Peptide, Aminoglycoside, and Quinolone Antibiotics in Pseudomonas aeruginosa PAO1 ». Antimicrobial Agents and Chemotherapy 50, n^o 5 (mai 2006) : 1615–22. http://dx.doi.org/10.1128/aac.50.5.1615-1622.2006.

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ABSTRACT Pseudomonas aeruginosa, a gram-negative bacterium of human pathogens, is noted for its environmental versatility, enormous metabolic capacity, and resistance to antibiotics. Overexpression of the outer membrane protein OprH and increased resistance to polycationic peptide antibiotics (e.g., polymyxin B) mediated by the PhoPQ two-component system on induction of a putative lipopolysaccharide (LPS) modification operon (PA3552-PA3559) have been reported as part of the adaptive responses to magnesium limitation in P. aeruginosa. Induction of the oprH-phoPQ operon and the LPS modification operon by exogenous spermidine was revealed from GeneChip analysis during studies of polyamine metabolism and was confirmed by the lacZ fusions of affected promoters. From the results of MIC measurements, it was found that addition of spermidine or other polyamines to the growth medium increased the MIC values of multiple antibiotics, including polycationic antibiotics, aminoglycosides, quinolones, and fluorescent dyes. MIC values of these compounds in the transposon insertion mutants of oprH, phoP, phoQ, and pmrB were also determined in the presence and absence of spermidine. The results showed that the spermidine effect on cationic peptide antibiotic and quinolone resistance was diminished in the phoP mutant only. The spermidine effect on antibiotics was not influenced by magnesium concentrations, as demonstrated by MICs and oprH::lacZ fusion studies in the presence of 20 μM or 2 mM magnesium. Furthermore, in spermidine uptake mutants, MICs of cationic peptide antibiotics and fluorescent dyes, but not of aminoglycosides and quinolones, were increased by spermidine. These results suggested the presence of a complicated molecular mechanism for polyamine-mediated resistance to multiple antibiotics in P. aeruginosa.

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Boudville, Neil, David W. Johnson, Junhui Zhao, Brian A. Bieber, Ronald L. Pisoni, Beth Piraino, Judith Bernardini et al. « Regional variation in the treatment and prevention of peritoneal dialysis-related infections in the Peritoneal Dialysis Outcomes and Practice Patterns Study ». Nephrology Dialysis Transplantation 34, n^o 12 (23 juillet 2018) : 2118–26. http://dx.doi.org/10.1093/ndt/gfy204.

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AbstractBackgroundPeritoneal dialysis (PD)-related infections lead to significant morbidity. The International Society for Peritoneal Dialysis (ISPD) guidelines for the prevention and treatment of PD-related infections are based on variable evidence. We describe practice patterns across facilities participating in the Peritoneal Dialysis Outcomes and Practice Patterns Study (PDOPPS).MethodsPDOPPS, a prospective cohort study, enrolled nationally representative samples of PD patients in Australia/New Zealand (ANZ), Canada, Thailand, Japan, the UK and the USA. Data on PD-related infection prevention and treatment practices across facilities were obtained from a survey of medical directors’.ResultsA total of 170 centers, caring for >11 000 patients, were included. The proportion of facilities reporting antibiotic administration at the time of PD catheter insertion was lowest in the USA (63%) and highest in Canada and the UK (100%). Exit-site antimicrobial prophylaxis was variably used across countries, with Japan (4%) and Thailand (28%) having the lowest proportions. Exit-site mupirocin was the predominant exit-site prophylactic strategy in ANZ (56%), Canada (50%) and the UK (47%), while exit-site aminoglycosides were more common in the USA (72%). Empiric Gram-positive peritonitis treatment with vancomycin was most common in the UK (88%) and USA (83%) compared with 10–45% elsewhere. Empiric Gram-negative peritonitis treatment with aminoglycoside therapy was highest in ANZ (72%) and the UK (77%) compared with 10–45% elsewhere.ConclusionsVariation in PD-related infection prevention and treatment strategies exist across countries with limited uptake of ISPD guideline recommendations. Further work will aim to understand the impact these differences have on the wide variation in infection risk between facilities and other clinically relevant PD outcomes.

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Lv, Boyan, Mengmeng Bian, Xuebing Huang, Fengqi Sun, Yuanyuan Gao, Yan Wang, Yajuan Fu, Bin Yang et Xinmiao Fu. « n-Butanol Potentiates Subinhibitory Aminoglycosides against Bacterial Persisters and Multidrug-Resistant MRSA by Rapidly Enhancing Antibiotic Uptake ». ACS Infectious Diseases 8, n^o 2 (1 février 2022) : 373–86. http://dx.doi.org/10.1021/acsinfecdis.1c00559.

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Stead, D. A., et R. M. E. Richards. « Sensitive high-performance liquid chromatographic assay for aminoglycosides in biological matrices enables the direct estimation of bacterial drug uptake ». Journal of Chromatography B : Biomedical Sciences and Applications 693, n^o 2 (juin 1997) : 415–21. http://dx.doi.org/10.1016/s0378-4347(97)00032-7.

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Henry-Stanley, Michelle J., Donavon J. Hess et Carol L. Wells. « Aminoglycoside inhibition of Staphylococcus aureus biofilm formation is nutrient dependent ». Journal of Medical Microbiology 63, n^o 6 (1 juin 2014) : 861–69. http://dx.doi.org/10.1099/jmm.0.068130-0.

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Biofilms represent microbial communities, encased in a self-produced matrix or extracellular polymeric substance. Microbial biofilms are likely responsible for a large proportion of clinically significant infections and the multicellular nature of biofilm existence has been repeatedly associated with antibiotic resistance. Classical in vitro antibiotic-susceptibility testing utilizes artificial growth media and planktonic microbes, but this method may not account for the variability inherent in environments subject to biofilm growth in vivo. Experiments were designed to test the hypothesis that nutrient concentration can modulate the antibiotic susceptibility of Staphylococcus aureus biofilms. Developing S. aureus biofilms initiated on surgical sutures, and in selected experiments planktonic cultures, were incubated for 16 h in 66 % tryptic soy broth, 0.2 % glucose (1× TSBg), supplemented with bactericidal concentrations of gentamicin, streptomycin, ampicillin or vancomycin. In parallel experiments, antibiotics were added to growth medium diluted one-third (1/3× TSBg) or concentrated threefold (3× TSBg). Following incubation, viable bacteria were enumerated from planktonic cultures or suture sonicates, and biofilm biomass was assayed using spectrophotometry. Interestingly, bactericidal concentrations of gentamicin (5 µg gentamicin ml−1) and streptomycin (32 µg streptomycin ml−1) inhibited biofilm formation in samples incubated in 1/3× or 1× TSBg, but not in samples incubated in 3× TSBg. The nutrient dependence of aminoglycoside susceptibility is not only associated with biofilm formation, as planktonic cultures incubated in 3× TSBg in the presence of gentamicin also showed antibiotic resistance. These findings appeared specific for aminoglycosides because biofilm formation was inhibited in all three growth media supplemented with bactericidal concentrations of the cell wall-active antibiotics, ampicillin and vancomycin. Additional experiments showed that the ability of 3× TSBg to overcome the antibacterial effects of gentamicin was associated with decreased uptake of gentamicin by S. aureus. Uptake is known to be decreased at low pH, and the kinetic change in pH of growth medium from biofilms incubated in 5 µg gentamicin ml−1 in the presence of 3× TSBg was decreased when compared with pH determinations from biofilms formed in 1/3× or 1× TSBg. These studies underscore the importance of environmental factors, including nutrient concentration and pH, on the antibiotic susceptibility of S. aureus planktonic and biofilm bacteria.

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Chopra, I. « Molecular mechanisms involved in the transport of antibiotics into bacteria ». Parasitology 96, S1 (janvier 1988) : S25—S44. http://dx.doi.org/10.1017/s0031182000085966.

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SUMMARYMany clinically useful antibacterial drugs have intracellular target sites. Therefore, in order to reach their targets, these compounds must be able to cross bacterial outer and cytoplasmic membranes. Considerable information is available on the mechanisms by which antibiotics cross bacterial membranes and, in many cases, it is now possible to define the molecular basis of their uptake. Passage of drugs across the outer membrane of Gram-negative bacteria can occur by diffusion through porin channels (e.g. β-lactams and tetracyclines), by facilitated diffusion using specific carriers (e.g. albomycin), or by self-promoted uptake (e.g. aminoglycosides and polymyxins). Transfer of antibiotics across the bacterial cytoplasmic membrane is usually mediated by active, carrier-mediated, transport systems normally operating to transport essential solutes into the cell. For example, the antibiotic streptozotocin bears sufficient structural resemblance toN-acetyl-D-glucosamine to be transported by the phosphoenolpyruvate : phosphotransferase system, and D-cycloserine is recognized by the D-alanine, proton motive force dependent transport system. However, in some cases (e.g. tetracycline) although carrier-mediated transport is implied by the observation that drug uptake is energy dependent, the nature of the membrane carrier(s) responsible is unknown. Knowledge acquired from studies on bacterial peptide transport has been successfully used to deliver (or smuggle) amino acid mimetics disguised as peptides into the bacterial cell. These amino acid mimetics, although often poorly transported in their own right, are frequently potent inhibitors of bacterial peptidoglycan or lipopolysaccharide synthesis once they have gained access to the interior of the cell.

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Lade, Harshad, Hwang-Soo Joo et Jae-Seok Kim. « Molecular Basis of Non-β-Lactam Antibiotics Resistance in Staphylococcus aureus ». Antibiotics 11, n^o 10 (8 octobre 2022) : 1378. http://dx.doi.org/10.3390/antibiotics11101378.

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Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most successful human pathogens with the potential to cause significant morbidity and mortality. MRSA has acquired resistance to almost all β-lactam antibiotics, including the new-generation cephalosporins, and is often also resistant to multiple other antibiotic classes. The expression of penicillin-binding protein 2a (PBP2a) is the primary basis for β-lactams resistance by MRSA, but it is coupled with other resistance mechanisms, conferring resistance to non-β-lactam antibiotics. The multiplicity of resistance mechanisms includes target modification, enzymatic drug inactivation, and decreased antibiotic uptake or efflux. This review highlights the molecular basis of resistance to non-β-lactam antibiotics recommended to treat MRSA infections such as macrolides, lincosamides, aminoglycosides, glycopeptides, oxazolidinones, lipopeptides, and others. A thorough understanding of the molecular and biochemical basis of antibiotic resistance in clinical isolates could help in developing promising therapies and molecular detection methods of antibiotic resistance.

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Griffith, J. K., T. Kogoma, D. L. Corvo, W. L. Anderson et A. L. Kazim. « An N-terminal domain of the tetracycline resistance protein increases susceptibility to aminoglycosides and complements potassium uptake defects in Escherichia coli. » Journal of Bacteriology 170, n^o 2 (1988) : 598–604. http://dx.doi.org/10.1128/jb.170.2.598-604.1988.

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Cheewapat, Rattiya, Jadsadaporn Redkimned, Sirikran Lekuthai, Thawatchai Kitti, Kannipa Tasanapak, Aunchalee Thanwisai, Sutthirat Sitthisak et al. « Genomic Landscape Reveals Chromosomally-Mediated Antimicrobial Resistome and Virulome of a High-Risk International Clone II Acinetobacter baumannii AB073 from Thailand ». Global Health, Epidemiology and Genomics 2024 (30 avril 2024) : 1–10. http://dx.doi.org/10.1155/2024/8872463.

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This study utilized integrative bioinformatics’ tools together with phenotypic assays to understand the whole-genome features of a carbapenem-resistant international clone II Acinetobacter baumannii AB073. Overall, we found the isolate to be resistant to seven antibiotic classes, penicillins, β-lactam/β-lactamase inhibitor combinations, cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and folate pathway antagonists. These resistance phenotypes are related to various chromosomal-located antibiotic resistance determinants involved in different mechanisms such as reduced permeability, antibiotic target protection, antibiotic target alteration, antibiotic inactivation, and antibiotic efflux. IC2 A. baumannii AB073 could not transfer antibiotic resistance by conjugation experiments. Likewise, mobilome analysis found that AB073 did not carry genetic determinants involving horizontal gene transfer. Moreover, this isolate also carried multiple genes associated with the ability of iron uptake, biofilm formation, immune invasion, virulence regulations, and serum resistance. In addition, the genomic epidemiological study showed that AB073-like strains were successful pathogens widespread in various geographic locations and clinical sources. In conclusion, the comprehensive analysis demonstrated that AB073 contained multiple genomic determinants which were important characteristics to classify this isolate as a successful international clone II obtained from Thailand.

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Williams-Hart, Tara, Xiaolin Wu et Kelly Tatchell. « Protein Phosphatase Type 1 Regulates Ion Homeostasis in Saccharomyces cerevisiae ». Genetics 160, n^o 4 (1 avril 2002) : 1423–37. http://dx.doi.org/10.1093/genetics/160.4.1423.

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Abstract Protein phosphatase type 1 (PP1) is encoded by the essential gene GLC7 in Saccharomyces cerevisiae. glc7-109 (K259A, R260A) has a dominant, hyperglycogen defect and a recessive, ion and drug sensitivity. Surprisingly, the hyperglycogen phenotype is partially retained in null mutants of GAC1, GIP2, and PIG1, which encode potential glycogen-targeting subunits of Glc7. The R260A substitution in GLC7 is responsible for the dominant and recessive traits of glc7-109. Another mutation at this residue, glc7-R260P, confers only salt sensitivity, indicating that the glycogen and salt traits of glc7-109 are due to defects in distinct physiological pathways. The glc7-109 mutant is sensitive to cations, aminoglycosides, and alkaline pH and exhibits increased rates of l-leucine and 3,3′-dihexyloxacarbocyanine iodide uptake, but it is resistant to molar concentrations of sorbitol or KCl, indicating that it has normal osmoregulation. KCl suppresses the ion and drug sensitivities of the glc7-109 mutant. The CsCl sensitivity of this mutant is suppressed by recessive mutations in PMA1, which encodes the essential plasma membrane H+ATPase. Together, these results indicate that Glc7 regulates ion homeostasis by controlling ion transport and/or plasma membrane potential, a new role for Glc7 in budding yeast.

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Omenako, Kwaku Anim, Anthony Enimil, Afia Frimpomaa Asare Marfo, Collins Timire, Palanivel Chinnakali, Ama Pokuaa Fenny, Kathiresan Jeyashree et Kwame Ohene Buabeng. « Pattern of Antimicrobial Susceptibility and Antimicrobial Treatment of Neonates Admitted with Suspected Sepsis in a Teaching Hospital in Ghana, 2021 ». International Journal of Environmental Research and Public Health 19, n^o 19 (10 octobre 2022) : 12968. http://dx.doi.org/10.3390/ijerph191912968.

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Neonatal sepsis is a life-threatening emergency, and empirical antimicrobial prescription is common. In this cross-sectional study of neonates admitted with suspected sepsis in a teaching hospital in Ghana from January–December 2021, we described antimicrobial prescription patterns, compliance with national standard treatment guidelines (STG), blood culture testing, antimicrobial resistance patterns and treatment outcomes. Of the 549 neonates admitted with suspected sepsis, 283 (52%) were males. Overall, 529 (96%) received empirical antimicrobials. Most neonates (n = 407, 76.9%) were treated empirically with cefuroxime + gentamicin, while cefotaxime was started as a modified treatment in the majority of neonates (46/68, 67.6%). Only one prescription complied with national STGs. Samples of 257 (47%) neonates underwent blood culture testing, of which 70 (27%) were positive. Isolates were predominantly Gram-positive bacteria, with coagulase-negative Staphylococcus and Staphylococcus aureus accounting for 79% of the isolates. Isolates showed high resistance to most penicillins, while resistance to aminoglycosides and quinolones was relatively low. The majority of neonates (n = 497, 90.5%) were discharged after successfully completing treatment, while 50 (9%) neonates died during treatment. Strengthening of antimicrobial stewardship programmes, periodic review of STGs and increased uptake of culture and sensitivity testing are needed to improve management of sepsis.

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Kurabayashi, Kumiko, Koichi Tanimoto, Shinobu Fueki, Haruyoshi Tomita et Hidetada Hirakawa. « Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions ». Antimicrobial Agents and Chemotherapy 59, n^o 10 (27 juillet 2015) : 6352–60. http://dx.doi.org/10.1128/aac.01176-15.

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ABSTRACTBecause a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a “last-resort option.” This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed thatEscherichia colistrains, including enterohemorrhagicE. coli(EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth ofE. coli. Our quantitative PCR analysis and a transport assay showed thatE. colicells grown under anaerobic conditions had higher levels of expression ofglpTanduhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream ofglpTanduhpT, suggesting that it is an activator of expression ofglpTanduhpTduring anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin towardE. coliunder anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.

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Fursova, Nadezhda K., Mikhail V. Fursov, Evgeny I. Astashkin, Anastasiia D. Fursova, Tatiana S. Novikova, Angelina A. Kislichkina, Angelika A. Sizova, Galina N. Fedyukina, Ivan A. Savin et Olga N. Ershova. « Multidrug-Resistant and Extensively Drug-Resistant Acinetobacter baumannii Causing Nosocomial Meningitis in the Neurological Intensive Care Unit ». Microorganisms 11, n^o 8 (6 août 2023) : 2020. http://dx.doi.org/10.3390/microorganisms11082020.

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Acinetobacter baumannii is one of the significant healthcare-associated meningitis agents characterized by multidrug resistance and a high mortality risk. Thirty-seven A. baumannii strains were isolated from thirty-seven patients of Moscow neuro-ICU with meningitis in 2013–2020. The death rate was 37.8%. Strain susceptibility to antimicrobials was determined on the Vitek-2 instrument. Whole-genome sequencing was conducted using Illumina technology; the sequence types (ST), capsular types (KL), lipooligosaccharide outer core locus (OCL), antimicrobial resistance genes, and virulence genes were identified. The prevalent ST was ST2, belonging to the international clone IC2, and rarer, ST1, ST19, ST45, ST78, ST106, and ST400, with prevalence of KL9 and OCL1. Twenty-nine strains belonged to multidrug-resistant (MDR) and eight extensively drug-resistant (XDR) categories. Genes conferring resistance to beta-lactams (blaPER, blaGES, blaADC, blaCARB, blaCTX-M, blaTEM, and blaOXA-types), aminoglycosides (aac, aad, ant, aph, and arm), tetracyclines (tet), macrolides (msr and mph), phenicols (cml, cat, and flo), sulfonamides (dfr and sul), rifampin (arr), and antiseptics (qac) were identified. Virulence genes of nine groups (Adherence, Biofilm formation, Enzymes, Immune evasion, Iron uptake, Regulation, Serum resistance, Stress adaptation, and Antiphagocytosis) were detected. The study highlights the heterogeneity in genetic clones, antimicrobial resistance, and virulence genes variability among the agents of A. baumannii meningitis, with the prevalence of the dominant international clone IC2.

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Borodina, Irina, Charlotte Schöller, Anna Eliasson et Jens Nielsen. « Metabolic Network Analysis of Streptomyces tenebrarius, a Streptomyces Species with an Active Entner-Doudoroff Pathway ». Applied and Environmental Microbiology 71, n^o 5 (mai 2005) : 2294–302. http://dx.doi.org/10.1128/aem.71.5.2294-2302.2005.

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ABSTRACT Streptomyces tenebrarius is an industrially important microorganism, producing an antibiotic complex that mainly consists of the aminoglycosides apramycin, tobramycin carbamate, and kanamycin B carbamate. When S. tenebrarius is used for industrial tobramycin production, kanamycin B carbamate is an unwanted by-product. The two compounds differ only by one hydroxyl group, which is present in kanamycin carbamate but is reduced during biosynthesis of tobramycin. 13C metabolic flux analysis was used for elucidating connections between the primary carbon metabolism and the composition of the antibiotic complex. Metabolic flux maps were constructed for the cells grown on minimal medium with glucose or with a glucose-glycerol mixture as the carbon source. The addition of glycerol, which is more reduced than glucose, led to a three-times-greater reduction of the kanamycin portion of the antibiotic complex. The labeling indicated an active Entner-Doudoroff (ED) pathway, which was previously considered to be nonfunctional in Streptomyces. The activity of the pentose phosphate (PP) pathway was low (10 to 20% of the glucose uptake rate). The fluxes through Embden-Meyerhof-Parnas (EMP) and ED pathways were almost evenly distributed during the exponential growth on glucose. During the transition from growth phase to production phase, a metabolic shift was observed, characterized by a decreased flux through the ED pathway and increased fluxes through the EMP and PP pathways. Higher specific NADH and NADPH production rates were calculated in the cultivation on glucose-glycerol, which was associated with a lower percentage of nonreduced antibiotic kanamycin B carbamate.

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