Are SHV β-Lactamases Universal in Klebsiella pneumoniae ?

The status of SHV-1 or related β-lactamases as “typical” ofKlebsiella pneumoniae prompted debate at the 39th Interscience Conference of Antimicrobial Agents and Chemotherapy. To test whether SHV-type enzymes are ubiquitous in this species, as previously asserted by one of us, (2) we screened 20 isolates identified as K. pneumoniae with API 20E tests (BioMerieux, Lyons, France). The isolates were obtained in 1997–1998 from intensive care units across Europe (1) and were chosen as broadly susceptible to β-lactam antibiotics including aztreonam (MIC ≤ 0.25 μg/ml), ceftazidime (MIC ≤ 0.25 μg/ml), ceftazidime plus clavulanic acid, 4 μg/ml (MIC ≤ 0.25 μg/ml), cefuroxime (MIC ≤ 4 μg/ml), ceftriaxone (MIC ≤ 0.12 μg/ml), piperacillin (MIC ≤ 8 μg/ml), piperacillin plus tazobactam, 4 μg/ml (MIC ≤ 4 μg/ml), cefoxitin (MIC ≤ 8 μg/ml), cefotetan (MIC ≤ 0.12 μg/ml), and meropenem (MIC ≤ 0.12 μg/ml). The MIC ratio of ceftazidime to ceftazidime plus clavulanic acid equalled unity, except for one isolate where it was 2, indicating the absence of extended-spectrum β-lactamases. The isolates were from 16 hospitals in eight European countries.