From the Guidelines
Bacteroides fragilis infections should be treated with metronidazole as the first-line antibiotic, typically administered at 500 mg orally three times daily for 7-14 days for mild to moderate infections, due to its effectiveness and the increasing resistance of B. fragilis to other antibiotics, as reported in the most recent study by Sartelli et al. 1.
Treatment Options
- Metronidazole is the preferred treatment for B. fragilis infections, with a dosage of 500 mg orally three times daily for 7-14 days for mild to moderate infections.
- For severe infections, intravenous metronidazole at 500 mg every 8 hours is recommended.
- Alternative treatments include carbapenems (such as imipenem or meropenem), beta-lactam/beta-lactamase inhibitor combinations (like piperacillin-tazobactam), or clindamycin, though resistance to clindamycin is increasing, as noted in the study by Sartelli et al. 1.
Resistance Patterns
- B. fragilis has shown increasing resistance to clindamycin and moxifloxacin, with rates of resistance at 19% and 27%, respectively, according to a US national survey (1997-2004) 1.
- The rates of resistance to carbapenems and beta-lactam-beta-lactamase inhibitor combinations are low, making them effective alternative treatments.
Clinical Considerations
- B. fragilis infections often occur as part of mixed bacterial infections following abdominal trauma, surgery, or perforation, and may present as intra-abdominal abscesses, peritonitis, or bacteremia.
- Prompt surgical drainage of abscesses along with appropriate antibiotic therapy is crucial for successful treatment of B. fragilis infections.
- The choice of empiric antibiotic regimens should be based on the clinical condition of the patients, the individual risk for infection by resistant pathogens, and the local resistance epidemiology, as recommended by Sartelli et al. 1.
From the Research
Bacteroides fragilis Infections
- Bacteroides fragilis is a type of anaerobic bacteria that can cause various infections, including endocarditis, osteomyelitis, lung abscess, empyema, peritonitis, septicemia, and pelvic infection 2
- The bacteria are often resistant to many commonly used antibiotics, making treatment challenging 3
Treatment Options
- Metronidazole is a effective agent in the treatment of B. fragilis infections, and can be used alone or in combination with aminoglycosides 2
- Other successful antimicrobial agents include clindamycin, chloramphenicol, and piperacillin, cefoxitin, and moxalactam can be used with an aminoglycoside or alone if no resistant organisms are revealed on culture and susceptibility testing 3
- Meropenem and imipenem have also been shown to be effective against B. fragilis, but some isolates may exhibit resistance or diminished susceptibility 4
Antimicrobial Resistance
- Antimicrobial resistance is a significant concern in the treatment of B. fragilis infections, with some studies showing high rates of resistance to certain antibiotics 5
- Previous exposure to broad-spectrum antibiotics, such as meropenem, has been associated with reduced susceptibility to these antibiotics 5
- Monitoring antimicrobial susceptibility in the gut microbiota may be important to detect increased levels of antimicrobial resistance in B. fragilis group bacteria 5
Metronidazole Dosage
- A study comparing once-daily versus multiple dose regimens of metronidazole found that once-daily dosing was as efficacious and not inferior to multiple-dosed regimens for the treatment of serious systemic infections where B. fragilis is an important co-pathogen 6
- The study suggested that once-daily metronidazole has pharmacokinetic and pharmaco-economic advantages 6