Photo Credit: Kateryna Kon

The following is a summary of “A seemingly considerable increase in antimicrobial resistance in the Bacteroides fragilis group from blood cultures – the second national study in Denmark,” published in the November 2024 issue of Infectious Disease by Florisson et al. 

Bacteroides fragilis group species, a leading cause of fatal anaerobic bacteremia, prompted a nationwide antimicrobial susceptibility study in Denmark in 2012.  

Researchers conducted a retrospective study to compare the antimicrobial susceptibility rates of piperacillin-tazobactam, meropenem, clindamycin, and metronidazole in B. fragilis group blood cultures between 2012 and 2022 in Denmark and to investigate whether susceptibility changes were linked to antimicrobial agent usage trends. 

They performed an antimicrobial susceptibility testing following EUCAST guidelines using the agar dilution and disc diffusion methods.  

The results showed a significant rise in resistance of the Bacteroides fragilis group (n = 234) to piperacillin-tazobactam, increasing from 8.5% in 2012 to 42.7% in 2022. Resistance to meropenem also grew from 3.4% to 10.7%. The increase in resistance for both piperacillin-tazobactam and meropenem was mainly attributed to a recent EUCAST breakpoint change, while metronidazole remained the most effective, with the lowest resistance rate at 0.4% (1 isolate). Piperacillin-tazobactam sales saw a corresponding rise of +130%, and meropenem sales remained stable.  

Investigators concluded the importance of routine antimicrobial susceptibility testing for B. fragilis group species and raised concerns about the efficacy of piperacillin-tazobactam monotherapy as empiric treatment for patients with abdominal sepsis. 

Source: tandfonline.com/doi/full/10.1080/23744235.2024.2425715