Abstract Introduction Bacteroides species are significant anaerobes that cause intra-abdominal infections. Recent data highlight increasing resistance, specifically to clindamycin (CLDM). However, the precise epidemiology of Bacteroides fragilis and non-fragilis remains unclear. Methods We retrospectively analyzed 528 obligate anaerobes were isolated from blood cultures at six major Japanese hospitals in between 2012 and 2022, with 102 B. fragilis and 72 non-B. fragilis isolates. Clinical characteristics and antimicrobial resistance were assessed. Drug resistance rates over time were analyzed using the Spearman rank correlation test. Results Compared to the B. fragilis group, non-B. fragilis group demonstrated higher resistance to CLDM (P = 0.006) and carbapenem (P = 0.005). Excluding deaths from underlying diseases, 30-day mortality rate was higher in the non-B. fragilis group than that in the B. fragilis group (P = 0.025). Risk factors in this group included carbapenem resistance (adjusted OR = 7.05, P = 0.017). Notably, carbapenem (P = 0.014 vs. P = 0.643) and tazobactam/piperacillin (TAZ/PIPC) resistance rates (P = 0.012 vs. P = 0.899) increased over time in the non-B. fragilis group, rather than the B. fragilis group. Conclusions Non-B. fragilis shows increasing resistance to key antibiotics and is linked to higher 30-day mortality compared to B. fragilis.
Kubo et al. (Wed,) studied this question.
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