Relationship between β-lactamase production and resistance phenotype in Klebsiella pneumoniae strains

초록

This study was designed to evaluate the resistance phenotypes of beta-lactamases-producing Klebsiella pneumoniae strains. The antibiotic susceptibility and beta-lactamase activity of K. pneumoniae strains, including antibiotic-sensitive K. pneumoniae (KPWT), ciprofloxacin-induced resistant K. pneumoniae (KPCIP) and clinically isolated K. pneumoniae strains (KPCI237, KPCI263 and KPCI272) were determined in the absence and presence of beta-lactamase inhibitors (BLI 489, sulbactam, clavulanate and tazobactam). All strains were highly resistant to ampicillin in the absence of beta-lactamase inhibitors (MIC >= 512 mu g mL(-1)). In the presence of clavulanate, the MICs of ampicillin and piperacillin against KPWT were decreased by > 64-fold and 4-fold, respectively. The resistance of KPCI263 to cefotaxime, ceftazidime, ceftriaxone and piperacillin were increased in the presence of BLI-489. The antibiotic susceptibility of KPCI237 to beta-lactams was not noticeably changed in the presence of beta-lactamase inhibitor (clavulanate, sulbactam or tazobactam). KPWT, KPCIP and KPCI272 were positive for bla(SHV), bla(AmpC) and bla(FOX/MOX); KPCI237 for bla(SHV) and bla(AmpC); and KPCI263 for bla(SHV) and bla(OXA-48). The antibiotic susceptibility corresponded well with the results obtained from dual disc diffusion assay, which was in good agreement with the beta-lactamase production. The results provide useful information for understanding the resistance phenotypes in association with beta-lactamase production.

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