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Beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca.

ABSTRACT: 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.

SUBMITTER: Fournier B

PROVIDER: S-EPMC163134 | biostudies-other | 1996 Feb

REPOSITORIES: biostudies-other

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beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca.

Fournier B B Lagrange P H PH Philippon A A

Antimicrobial agents and chemotherapy 19960201 2

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 transit ...[more]

PMID: 8834898

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Project description:Klebsiella oxytoca complex (KoC) species may overproduce their chromosomal class A OXY β-lactamases, conferring reduced susceptibility to piperacillin-tazobactam, expanded-spectrum cephalosporins and aztreonam. Moreover, since clavulanate maintains its ability to inhibit these enzymes, the resulting resistance phenotype may falsely resemble the production of acquired extended-spectrum β-lactamases (ESBLs). In this work, a collection of 44 KoC strains of human and animal origin was characterized with whole-genome sequencing (WGS) and broth microdilution (BMD) susceptibility testing. Comparison of ESBL producers (n = 11; including CTX-M-15 [n = 6] and CTX-M-1 [n = 5] producers) and hyperproducers of OXYs (n = 21) showed certain phenotypic differences: piperacillin-tazobactam (MIC90s: 16 versus >64 μg/mL), cefotaxime (MIC90s: 64 versus 4 μg/mL), ceftazidime (MIC90s: 32 versus 4 μg/mL), cefepime (MIC90s: 8 versus 4 μg/mL) and associated resistance to non-β-lactams (e.g., trimethoprim-sulfamethoxazole: 90.9% versus 14.3%, respectively). However, a clear phenotype-based distinction between the two groups was difficult. Therefore, we evaluated 10 different inhibitor-based confirmatory tests to allow such categorization. All tests showed a sensitivity of 100%. However, only combination disk tests (CDTs) with cefepime/cefepime-clavulanate and ceftazidime/ceftazidime-clavulanate or the double-disk synergy test (DDST) showed high specificity (100%, 95.5%, and 100%, respectively). All confirmatory tests in BMD or using the MIC gradient strip did not perform well (specificity, ≤87.5%). Of note, ceftazidime/ceftazidime-avibactam tests also exhibited low specificity (CDT, 87.5%; MIC gradient strip, 77.8%). Our results indicate that standard antimicrobial susceptibility profiles can raise some suspicion, but only the use of cefepime/cefepime-clavulanate CDT or DDST can guarantee distinction between ESBL-producing KoC strains and those hyperproducing OXY enzymes.

Dataset Information

Beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca.

Publications

beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca.

Similar Datasets

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