151. SHV-Type Extended-Spectrum Beta-Lactamase Production Is Associated with Reduced Cefepime Susceptibility in Enterobacter cloacae
- Author
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Szabo´, Do´ra, Bonomo, Robert A., Silveira, Fernanda, Pasculle, A. William, Baxter, Carla, Linden, Peter K., Hujer, Andrea M., Hujer, Kristine M., Deeley, Kathleen, and Paterson, David L.
- Abstract
ABSTRACTCefepime is a potentially useful antibiotic for treatment of infections with Enterobacter cloacae. However, in our institution the MIC90for E. cloacaebloodstream isolates is 16 µg/ml. PCR amplification of blagenes revealed that one-third (15/45) of E. cloacaebloodstream isolates produced SHV-type extended-spectrum beta-lactamases (ESBLs) in addition to hyperproduction of AmpC-type beta-lactamases. The majority (11/15) of ESBL producers also produced the TEM-1 beta-lactamase. The SHV types included SHV-2, -5, -7, -12, -14, and -30. All but two of the ESBL-producing E. cloacaeisolates, but none of the non-ESBL-producing strains, had MICs of cefepime of =2 µg/ml. The MIC90for cefepime for ESBL-producing strains was 64 µg/ml, while for non-ESBL producers it was 0.5 µg/ml. Using current Clinical and Laboratory Standards Institute breakpoints for cefepime, two thirds (10/15) of ESBL-producing isolates would have been regarded as susceptible to cefepime. Phenotypic ESBL detection methods were generally unreliable with these E. cloacaeisolates. Based on these results, pharmacokinetic, pharmacodynamic, and clinical reevaluation of cefepime breakpoints for E. cloacaemay be prudent.
- Published
- 2005
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