Journal of Antimicrobial Chemotherapy (2002) 49, 69-76
© 2002 The British Society for Antimicrobial Chemotherapy
Antimicrobial susceptibilities among clinical isolates of extended-spectrum cephalosporin-resistant Gram-negative bacteria in a Taiwanese University Hospital
a Section of Infectious Diseases, Department of Internal Medicine, and b Department of Laboratory Medicine, National Taiwan University Hospital c School of Medical Technology, National Taiwan University College of Medicine, 7 Chun-Shan South Road, Taipei, Taiwan
Infections caused by Gram-negative bacteria with resistance to extended-spectrum cephalosporins require the identification of effective alternative antimicrobial therapy. To determine the role of other pre-existing or currently available antimicrobial agents in treating infections caused by these multidrug-resistant pathogens, we evaluated the in vitro susceptibilities of these agents in 411 non-duplicate isolates of extended-spectrum cephalosporin-resistant Gram-negative bacteria recovered between January 1999 and December 1999 in a major teaching hospital in Taipei, Taiwan. These isolates included cefotaxime-resistant (MICs 2 mg/L) Escherichia coli (66 isolates) and Klebsiella pneumoniae (77 isolates); cefotaxime-resistant (MICs 64 mg/L) Enterobacter cloacae (59 isolates), Serratia marcescens (52 isolates) and Citrobacter freundii (52 isolates); and ceftazidime-resistant (MICs 64 mg/L) Pseudomonas aeruginosa (50 isolates) and Acinetobacter baumannii (55 isolates). Overall, carbapenems (imipenem and meropenem) had good activity against the cefotaxime-resistant Enterobacteriaceae tested (>90% of isolates were susceptible). However, carbapenems had limited activity against the ceftazidime-resistant P. aeruginosa (only 4% of isolates were susceptible) and A. baumannii (51–56% of isolates were susceptible). Among the E. coli and K. pneumoniae isolates tested, 33.3% and 58.4%, respectively, exhibited extended-spectrum ß-lactamase phenotype, determined by the double disc method. Over 80% of cefotaxime-resistant E. cloacae and C. freundii were susceptible to cefepime, but this agent had limited activity against other bacteria tested. Susceptibilities of these isolates to ciprofloxacin varied, ranging from 25% for A. baumannii to 92% for E. cloacae. Newer fluoroquinolones (moxifloxacin and trovafloxacin) had equal or less activity against these organisms, except for A. baumannii for which their MIC90s (8–16 mg/L) were four- to 16-fold less than that of ciprofloxacin (MIC90 128 mg/L).
* Corresponding author. Tel: +886-2-2312-3456, ext. 5363; Fax: +886-2-2322-4263; E-mail: hsporen{at}ha.mc.ntu.edu.tw