In-vitro activity of cefepime and other broad-spectrum antimicrobials against several groups of gramnegative bacilli and Staphylococcus aureus

The in vitro activity of cefepime was compared with that of amikacin, cefta zidime, imipenem, ciprofloxacin, and piperacillin-tazobactarn by using the E-test against five groups of carefully selected organisms: Klebsiella pneu moniae (68 isololates), Pseudomonas aeruginosa (62), methicillin-susceptibl e Staphylococcus aureus (MSSA) (60), and two groups of Enterobacteriaceae ( 60 and 62 isolates, respective ly). The bacteria were subdivided according to whether the infection was nosocomial or community-acquired, applying acc epted and predefined criteria. These isolates were obtained from patients a dmitted to our medical center throughout 1998. We retrospectively compared antimicrobial susceptibilities of the study sample with those of the +/- 30 00 bacterial strains isolated from blood stream infections since 1990: the study sample appeared to represent adequately the clinical databank. Presen ce of extended-spectrum p-lactamase (ESBL) was determined in all groups of Enterobacteriaceae with the ESBL screening E-test strip. Of the 252 Gram-ne gative bacilli tested, 242 (96%) were susceptible to cefepime, whereas only 168 (67%) were susceptible to ceftazidime, 211 (84%) to amikacin, and 220 (87%) to piperacillin-tazobactam (p < 0.001). Imipenem was slightly superio r to cefepime with only seven isolates resistant (3%), six of which were P. aeruginosa. Cefepime was more active against Enterobacteriaceae than cefta zidime (93% vs. 72%, p < 0.001). This superiority was most evident against nosocomial strains of K. pneumoniae, against which cefepime was > three tim es more active than ceftazidime. The high level of resistance seen in nosoc omial isolates of K. pneumoniae is consistent with high rates of of product ion (69%, compared with 15-26% in of her Enterobacteriaceae). The MIG,, of cefepime to methicillin-sensitive S. aureus was 1.5 mu g/mL, whereas that o f ceftazidime was 4 mu g/mL; the susceptibility rate of both was 100%. In c onclusion, cefepime possesses in vitro potencies against MSSA and current c linical strains of Gram-negative bacilli, many of which harbor resistance t o other antimicrobial agents. Hence, it seems very suitable for empiric cov erage of serious nosocomial infections. (C) 1999 Elsevier Science Inc.