Inhibitor-resistant TEM  -lactamases: phenotypic, genetic and biochemical characteristics

Chaibi, El Bachir; Sirot, D.; Paul, G.; Labia, Roger

doi:10.1093/jac/43.4.447

Cited by 223 publications

(177 citation statements)

References 57 publications

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“…Previous studies with various TEM-1 Arg244 mutants have shown a similar effect upon K m with penicillin substrates. 28,29 The K m values for cephalothin and cephalosporin C were too high to be reliably determined and so the relative contribution of K m and k cat upon catalytic efficiency of TEM-1 Arg244Ala is unknown for these substrates. However, the catalytic efficiency of the Arg244Ala enzyme, relative to wild-type TEM-1, was reduced >1000-fold for the cephalothin and cephalosporin C substrates (Table III).…”

Section: Resultsmentioning

confidence: 99%

Analysis of the plasticity of location of the Arg244 positive charge within the active site of the TEM‐1 β‐lactamase

2009

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A large number of b-lactamases have emerged that are capable of conferring bacterial resistance to b-lactam antibiotics. Comparison of the structural and functional features of this family has refined understanding of the catalytic properties of these enzymes. An arginine residue present at position 244 in TEM-1 b-lactamase interacts with the carboxyl group common to penicillin and cephalosporin antibiotics and thereby stabilizes both the substrate and transition state complexes. A comparison of class A b-lactamase sequences reveals that arginine at position 244 is not conserved, although a positive charge at this structural location is conserved and is provided by an arginine at positions 220 or 276 for those enzymes lacking arginine at position 244. The plasticity of the location of positive charge in the b-lactamase active site was experimentally investigated by relocating the arginine at position 244 in TEM-1 b-lactamase to positions 220, 272, and 276 by site-directed mutagenesis. Kinetic analysis of the engineered b-lactamases revealed that removal of arginine 244 by alanine mutation reduced catalytic efficiency against all substrates tested and restoration of an arginine at positions 272 or 276 partially suppresses the catalytic defect of the Arg244Ala substitution. These results suggest an evolutionary mechanism for the observed divergence of the position of positive charge in the active site of class A b-lactamases.

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Section: Resultsmentioning

confidence: 99%

Analysis of the plasticity of location of the Arg244 positive charge within the active site of the TEM‐1 β‐lactamase

2009

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“…IRT-producing mutants have been reported in both general practice and hospitals. 10,11 Nosocomial outbreaks of Klebsiella spp. resistant to the third-generation cephalosporins due to the production of ESBL have been reported worldwide.…”

Section: Discussionmentioning

confidence: 99%

Antibiotic Consumption and Development of Resistance among Gram-Negative Bacilli in Intensive Care Units in Oman

2000

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Since the discovery of antimicrobial agents, microorganisms have developed virtually unlimited resistance to them.1 Hospitals and particularly intensive care units are an important breeding ground for the development of antibiotic-resistant bacteria. This is the consequence of heavy antibiotic use. In addition, a high-density patient population in frequent contact with health care staff and the attendant risk of cross-infection contributes to the spread of antibiotic-resistant micro-organisms. This in turn increases the morbidity and mortality associated with infections, and contributes to rising costs of health care.2,3 The aim of this study was to investigate the prevalence of antibiotic resistance among gram-negative bacteria in relation to antibiotic use in the intensive care unit (ICU) at the Royal Hospital, the main referral hospital in Oman. Materials and MethodsThe Royal Hospital is a 630-bed tertiary care hospital consisting of major medical and surgical departments, in addition to specialized units such as intensive care, neonatal, renal, cardiac and oncology. The intensive care unit (ICU) at the Royal Hospital is a general unit admitting both medical and surgical patients, and has a capacity of 12 beds divided between adults and pediatrics. Specimen Collection and Identification of IsolatesOne hundred consecutive gram-negative bacterial isolates from different sites were collected from patients admitted to the adult ICU at the Royal Hospital. The clinical significance of the isolates was confirmed by analysis of patients' records and discussion with the treating clinician. All bacterial strains were identified by their colonial morphology, gram reaction, the oxidized and other biochemical reactions as performed by either API 20E, or API 20NE (bioMerieux, France). Susceptibility TestingThe susceptibilities of the strains to 12 antibiotics (co-amoxiclav, cefuroxime, cefotaxime, ceftriaxone, ceftazidime, aztreonam, piperacillin, piperacillin/tazobactam, imipenem, gentamicin, amikacin, and ciprofloxacin) were performed by determining the minimum inhibitory concentration (MIC), using the E-test (AB BIODISK, Sweden), with E. coli NCTC 10418 and P. aeruginosa NCTC 10662 as controls. The interpretation standards for MICs of the NCCLS were used to determine antibiotic susceptibilities. 4 To detect extended spectrum β-lactamases (ESBL), ceftazidime-resistant strains of E. coli and Klebsiella spp. were further tested against ceftazidime/clavulanic acid. Isolates with a reduction of ceftazidime MIC by >3 two-fold dilutions in the presence of clavulanic acid were considered ESBL producers, and thus resistant to other cephalosporins. Antibiotic ConsumptionThe quantities of antibiotics consumed in the ICU during the period of the study were obtained from the hospital pharmacy records, and the numbers of the patients discharged were obtained from the hospital records. The estimated days of antibiotic treatment were calculated from the antibiotic daily dose, the total amount consumed and the number of patients who lef...

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“…Furthermore, because expression of resistance is affected by multiple factors, the same ESBL can produce different resistance phenotypes, depending on the bacterial carrier and test conditions (17,23). There are also increasing reports of more-complex ESBL phenotypes that include additional mechanisms of resistance, such as AmpC-type enzyme production (both chromosomal and plasmid-mediated), TEM and SHV beta-lactamases with reduced affinities for beta-lactamase inhibitors, hyperproduction of penicillinase, and porin changes (4,6,8,17,23,26,32,34,39,49,(52)(53)(54).…”

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confidence: 99%

Evaluation of the New VITEK 2 Extended-Spectrum Beta-Lactamase (ESBL) Test for Rapid Detection of ESBL Production in Enterobacteriaceae Isolates

Spanu¹,

Sanguinetti²,

Tumbarello

et al. 2006

J Clin Microbiol

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Extended-spectrum beta-lactamases (ESBLs) are a large, rapidly evolving group of enzymes that confer resistance to oxyimino cephalosporins and monobactams and are inhibited by clavulanate. Rapid reliable detection of ESBL production is a prerequisite for successful infection management and for monitoring resistance trends and implementation of intervention strategies. We evaluated the performance of the new VITEK 2 ESBL test system (bioMérieux, Inc, Hazelwood, Mo.) in the identification of ESBL-producing Enterobacteriaceae isolates. We examined a total of 1,129 clinically relevant Enterobacteriaceae isolates (including 218 that had been previously characterized). The ESBL classification furnished by the VITEK 2 ESBL test system was concordant with that of the comparison method (molecular identification of beta-lactamase genes) for 1,121 (99.3%) of the 1,129 isolates evaluated. ESBL production was correctly detected in 306 of the 312 ESBL-producing organisms (sensitivity, 98.1%; positive predictive value, 99.3%). False-positive results emerged for 2 of the 817 ESBL-negative isolates (specificity, 99.7%; negative predictive value, 99.3%). VITEK 2 ESBL testing took 6 to 13 h (median, 7.5 h; mean ؎ SD, 8.2 ؎ 2.39 h). This automated short-incubation system appears to be a rapid and reliable tool for routine identification of ESBL-producing isolates of Enterobacteriaceae.Extended-spectrum beta-lactamases (ESBLs) are a large, rapidly evolving group of plasmid-mediated enzymes (4,5,17,23,30,33,45) that confer resistance to the oxyimino cephalosporins and monobactams. They are inhibited by clavulanate (CA), sulbactam, or tazobactam. Originally observed in Escherichia coli and Klebsiella spp., ESBL production has now been documented in other gram-negative bacilli, including Enterobacter spp., Proteus mirabilis, and Providencia stuartii (4,23,25,30,45).Laboratory detection of ESBL production can be problematic (4,23,27,30,33,45,49,52). The presence of these enzymes does not always elevate MICs of oxyimino cephalosporins and monobactams to levels indicative of resistance defined by the Clinical Laboratory Standards Institute (CLSI) (2, 10). Furthermore, because expression of resistance is affected by multiple factors, the same ESBL can produce different resistance phenotypes, depending on the bacterial carrier and test conditions (17, 23). There are also increasing reports of more-complex ESBL phenotypes that include additional mechanisms of resistance, such as AmpC-type enzyme production (both chromosomal and plasmid-mediated), TEM and SHV beta-lactamases with reduced affinities for beta-lactamase inhibitors, hyperproduction of penicillinase, and porin changes (4,6,8,17,23,26,32,34,39,49,(52)(53)(54).Several molecular methods are available for research and epidemiological studies, but they are not appropriate for routine detection of ESBL production in clinical settings (9, 36). Two phenotypic strategies can be used to detect ESBL expression in clinical settings. One involves analysis of MIC patterns with specific software...

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Inhibitor-resistant TEM -lactamases: phenotypic, genetic and biochemical characteristics

Cited by 223 publications

References 57 publications

Analysis of the plasticity of location of the Arg244 positive charge within the active site of the TEM‐1 β‐lactamase

Analysis of the plasticity of location of the Arg244 positive charge within the active site of the TEM‐1 β‐lactamase

Antibiotic Consumption and Development of Resistance among Gram-Negative Bacilli in Intensive Care Units in Oman

Evaluation of the New VITEK 2 Extended-Spectrum Beta-Lactamase (ESBL) Test for Rapid Detection of ESBL Production in Enterobacteriaceae Isolates

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