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

Abstract

This study was designed to evaluate the resistance phenotypes of β-lactamases-producing Klebsiella pneumoniae strains. The antibiotic susceptibility and β-lactamase activity of K. pneumoniae strains, including antibiotic-sensitive K. pneumoniae (KP^WT), ciprofloxacin-induced resistant K. pneumoniae (KP^CIP) and clinically isolated K. pneumoniae strains (KP^CI237, KP^CI263 and KP^CI272) were determined in the absence and presence of β-lactamase inhibitors (BLI 489, sulbactam, clavulanate and tazobactam). All strains were highly resistant to ampicillin in the absence of β-lactamase inhibitors (MIC≥ 512 μg mL⁻¹). In the presence of clavulanate, the MICs of ampicillin and piperacillin against KP^WT were decreased by > 64-fold and 4-fold, respectively. The resistance of KP^CI263 to cefotaxime, ceftazidime, ceftriaxone and piperacillin were increased in the presence of BLI-489. The antibiotic susceptibility of KP^CI237 to β-lactams was not noticeably changed in the presence of β-lactamase inhibitor (clavulanate, sulbactam or tazobactam). KP^WT, KP^CIP and KP^CI272 were positive for bla_SHV, bla_AmpC and bla_FOX/MOX; KP^CI237 for bla_SHV and bla_AmpC; and KP^CI263 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 β-lactamase production. The results provide useful information for understanding the resistance phenotypes in association with β-lactamase production.

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