In vitro activity of ceftazidime, cefepime and imipenem on 1,005 Pseudomonas aeruginosa clinical isolates either susceptible or resistant to beta-lactams

Background: Recently, new 'fourth-generation' cephalosporins, such as cefepime and cefpirome, were introduced into antibacterial chemotherapy. Methods: In order to explore whether these new cephalosporins offer real advantages against Pseudomonas aeruginosa, we matched the in vitro activity of cefepime with that of ceftazidime and imipenem as reference compounds. Results: Among the 1,005 clinical isolates tested, 86.6% were susceptible to ceftazidime, whereas 80.7 and 76.9% were susceptible to imipenem and cefepime, respectively. Furthermore, the activity of the three compounds against a significant number of clinical isolates of P. aeruginosa expressing different resistance mechanisms to beta-lactam antibiotics was investigated. Among these isolates, 62.5% were still susceptible to ceftazidime, and 52.1 and 38.7% were inhibited by imipenem and cefepime, respectively. Conclusion: Ceftazidime and imipenem retained their activity against the majority of clinical P. aeruginosa isolates collected in Italy. Cefepime did not offer competitive advantages in terms of in vitro activity. Copyright (C) 2000 S. Karger AG, Basel.