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Increasing Resistance Among Anaerobes in Taiwan

A surveillance study from Taiwan demonstrated increasing resistance among anaerobes to several commonly used antianaerobic antibiotics, including carbapenems.

Because susceptibility testing of anaerobes is not routinely performed, data from surveillance studies are important in guiding antibiotic selection. Investigators in Taiwan recently conducted a surveillance study on clinical isolates of commonly encountered anaerobes, collected from 2000 through 2007, and on Bacteroides fragilis isolates associated with nosocomial infections, collected from 1990 through 2006. Bacteremia-associated isolates from 2006 were also evaluated.

Overall, susceptibilities to ampicillin-sulbactam, cefmetazole, and clindamycin decreased during the study period. Metronidazole, piperacillin-tazobactam, carbapenems, and chloramphenicol generally retained good activity against isolates of common anaerobes, although some trends in emerging resistance were noted compared with 1998–2000 (Antimicrob Agents Chemother 2002; 46:2908).

Nonsusceptibility to carbapenems, although uncommon, was seen at higher rates than in previous studies, especially among bacteremia-related isolates of Fusobacterium species, Prevotella species, and B. fragilis. Moxifloxacin nonsusceptibility was seen in 7% to 25% of bacteremia-associated anaerobic isolates; cefmetazole susceptibility in nosocomial isolates of B. fragilis decreased significantly during the study period (from 72% in 1999 to 14% in 2006). Bacteroides thetaiotaomicron isolates demonstrated decreased susceptibility to several antibiotics compared with 1998–2000.

Comment: Increases in nonsusceptibility to ampicillin-sulbactam, cefmetazole, and clindamycin in Taiwan suggest that these agents might not be good empirical options when anaerobic coverage is needed. Increased carbapenem nonsusceptibility, albeit uncommon, is concerning and bears close monitoring. These trends show the necessity of monitoring antimicrobial susceptibility among anaerobic bacteria.

— Lynn L. Estes, PharmD

Published in Journal Watch Infectious Diseases September 3, 2008

Citation(s):

Liu C-Y et al. Increasing trends in antimicrobial resistance among clinically important anaerobes and Bacteroides fragilis isolates causing nosocomial infections: Emerging resistance to carbapenems. Antimicrob Agents Chemother 2008 Sep; 52:3161.

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