Trends in antimicrobial resistance among Bacteroides species and Parabacteroides species in the United States from 2010-2012 with comparison to 2008-2009

- Five year comparison of the in-vitro susceptibility of Bacteroides and Parabacteroides species in the United States.
- Resistance to carbapenems and beta-lactam/beta-lactamase inhibitor combinations remains very uncommon.
- Resistance to moxifloxacin and clindamycin remain high and have increased from 2008 to 2012.
- No resistance to metronidazole detected in this survey.
- Species and antibiotic susceptibility associations remain unchanged.

The susceptibility trends for Bacteroides fragilis and related species against various antibiotics were determined using data from 3 years of surveillance (2010-2012) on 779 isolates referred by 7 medical centers. The antibiotic test panel included imipenem, ertapenem, meropenem, ampicillin-sulbactam, piperacillin-tazobactam, cefoxitin, clindamycin, moxifloxacin, tigecycline, linezolid, chloramphenicol and . MICs were determined using the agar dilution CLSI reference method. Carbapenem resistance remained low (range 1.1%-2.5%) and unchanged from 2008 to 9 through 2010-2012. Resistance also remained low to the beta-lactam/beta-lactamase inhibitor combinations (1.1%-4.4%). While resistance to clindamycin and moxifloxacin remained high; rates were lower for B. fragilis in 2010-12 (24% and 19% respectively) compared to the earlier time frame of 2008-9 (29% and 35% respectively for the earlier time frame). There were notable species and resistance associations which have been demonstrated previously. No resistance to metronidazole or chloramphenicol resistance was seen. These data demonstrate the continued variability in resistance among Bacteroides and Parabacteroides species, but do demonstrate that carbapenems and beta-lactam/beta-lactamase inhibitor combinations remain very active throughout the United States.