In vitro activities of 16 antimicrobial agents against clinical isolates of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in two regional hospitals in Taiwan

Chun-Hsing Liao¹, Wang-Huei Sheng¹, Jann-Tay Wang¹, Hsin-Yun Sun¹, Hua-Kung Wang², Po-Ren Hsueh³, Yee-Chun Chen¹, Shan-Chwen Chang^1
1Department of Internal Medicine, National Taiwan University Hospital, Taipei; ²Department of Internal Medicine, En-Chu-Kong Hospital, Taipei; and ³Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan

Received: April 18, 2005 Revised: June 20, 2005 Accepted: August 16, 2005

Corresponding author: Shan-Chwen Chang, Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei, Taiwan. E-mail:

Background and Purpose: Infections due to extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EC and ESBL-KP) have become an important clinical problem. Local knowledge of antimicrobial susceptibilities of these organisms is important for implementation of effective hospital anti-infective policies.
Methods: We analyzed the activities of various antimicrobial agents against recent isolates of ESBL-EC and ESBL-KP from 2 regional hospitals using the agar dilution method to determine minimal inhibitory concentrations (MICs). A total of 80 strains of ESBL-EC and 101 strains of ESBL-KP collected during 2003 and 2004 were included in the study.
Results: The MICs of all carbapenems were relatively low, with almost all isolates being susceptible. In contrast, only 30.0% of ESBL-EC and 36.6% of ESBL-KP were susceptible to ciprofloxacin. Flomoxef and cefmetazole were the most active cephamycins (88.8% and 90.0% ESBL-EC and 93.1% and 87.1% ESBL-KP susceptible, respectively), followed by ceftibuten (85.0% and 80.2%) and cefoxitin (42.5% and 49.5%). A cefepime MIC ?8 mg/L was found in 77.5% of ESBL-EC and 73.3% of ESBL-KP isolates. The susceptible rates to amikacin and isepamicin were both 81.3% for ESBL-EC; 72.3% and 73.3% for ESBL-KP. Inter-hospital differences in susceptibilities were demonstrated for several antimicrobials.
Conclusions: The inter-hospital variation of these data emphasizes the need for monitoring of antimicrobial susceptibility profiles at the individual hospital level and to establish rationales supporting policy for treating infections caused by ESBL-producing bacteria.

Key words: Aminoglycosides, beta-lactamases, carbapenems, cephalosporins, cephamycins, fluoroquinolones

J Microbiol Immunol Infect 2006;39:59-66.