In-vitro activity of oxymino-cephalosporins with and without sulbactam against Class A Extended-spectrum β-lactamase producing E.coli

Abstract

Objectives: The primary aim of this study was to determine the activities of ceftazidime and cefepime combined to sulbactam against class A extended-spectrum β lactamases (ESBLs). Materials and methods: Eight university hospitals participated to the study by submitting isolates those were recovered during a six-month period in 2010 from various clinical materials. Sulbactam was tested in two fixed concentrations of 4 mg/l and 8 mg/l. Isolates showing a fourfold or more decrease in the MIC of an oxyimino-cephalosporin with sulbactam were defined as ESBL producers. Isolates were screened for CTX-M group 1 extended-spectrum β lactamases by PCR. Results: A total of 149 ESBL-positive E.coli were studied. Isolates were uniformly susceptible to carbapenems and highly resistant to ciprofloxacin. According to CLSI breakpoints, 28% (42/149) of isolates were susceptible to ceftazidime and 32% (47/149) to cefepime. With 4 mg/L and 8 mg/L sulbactam supplement, ceftazidime susceptibility rose to 69% (103/149) and 88% (131/149), while cefepime susceptibility rose to 86 % (128/149) and 95% (141/149), respectively. PCR screening revealed that 63% (94/149) of the isolates were positive for blaCTX-M and 38% (36/94) of these were on the O25b-ST131 clone. Conclusion: Ceftazidime plus sulbactam and cefepime plus sulbactam showed remarkable activity against ESBL-positive E.coli.