Comparison of susceptibility to extended-spectrum β-lactam antibiotics and ciprofloxacin among gram-negative bacilli isolated from intensive care units

The in vitro activities of extended-spectrum β-lactam antibiotics (including piperacillin, cefotaxime, ceftriaxone, ceftazidime, cefepime, imipenem, and meropenems) were assessed and compared with the activity of ciprofloxacin against 366 clinical Gram-negative bacilli isolates from the intensive care units of Taichung Veterans General Hospital. The most prevalent species isolated were Pseudomonas aeruginosa and Acinetobacter baumannii. The activities of ceftazidime, cefepime, imipenem, and meropenem against these isolates were comparable to that of ciprofloxacin. Meropenem was found to be the most potent extended-spectrum β-lactam antibiotic tested and the MIC 50s and MIC 90s for most of these multiresistant strains were lower than those of imipenem, ceftazidime, and cefepime, except for Stenotrophomonas maltophilia. The extended-spectrum β-lactam antibiotics that were still active against S. maltophilia were piperacillin and ceftazidime. More than 50% of Enterobacter spp. were resistant to third-generation cephalosporins and piperacillin, but they remained susceptible to carbapenems and cefepime.