In vitro susceptibilities of aerobic and facultative anaerobic Gram-negative bacilli isolated from patients with intra-abdominal infections at a medical center in Taiwan: results of the Study for Monitoring Antimicrobial Resistance Trends (SMART) 2002-2006

Abstract

Background and purpose: The Study for Monitoring Antimicrobial Resistance Trends (SMART) was initiated to monitor the in vitro antimicrobial susceptibility of aerobic and facultative anaerobic Gram-negative bacilli (GNB) isolated from patients with intra-abdominal infections (IAI). This report summarizes the SMART data from 1 of the study centers from 2002 to 2006.

Methods: 492 Gram-negative isolates were collected from 482 patients with IAI. Susceptibilities of these isolates to 12 antimicrobial agents were determined using the broth microdilution method.

Results: Enterobacteriaceae comprised 68.3% of the isolates (n = 336). The 4 main species were Klebsiella spp. (n = 129; 26.2%), Escherichia coli (n = 122; 24.8%), Enterobacter spp. (n = 36; 7.3%), and Aeromonas hydrophila (n = 35; 7.1%). The commonest glucose non-fermentative GNB were Acinetobacter baumannii (n = 46; 9.3%) and Pseudomonas aeruginosa (n = 35; 7.1%). Extended-spectrum beta-lactamase (ESBL) production was detected in 70 Enterobacteriaceae isolates (70/336; 21%). The ESBL phenotype was exhibited by 23% of Klebsiella pneumoniae, 26% of E. coli, and 19% of Enterobacter spp. The highest rate of ESBL production was found in 2005 for E. coli (38%) and in 2003 for Klebsiella spp. (38%) and Enterobacter spp. (40%). The incidence of ESBL-producing isolates declined in 2005 and 2006. Low susceptibility rates of E. coli isolates to ciprofloxacin (58%) and levofloxacin (64%) were noted. Ertapenem (99%), imipenem (99%), and amikacin (94%) were the most potent agents against Enterobacteriaceae spp.

Conclusions: Continuous surveillance is crucial to monitor the trend of antimicrobial resistance patterns among GNB isolated from IAI.