Bacteroides gracilis, an important anaerobic bacterial pathogen

Area of Science:

• Microbiology
• Clinical Bacteriology
• Infectious Diseases

Background:

• Anaerobic gram-negative bacilli, including Bacteroides ureolyticus, B. gracilis, Campylobacter concisus, and Wolinella sp., are clinically significant.
• These organisms are often recovered from various human infections.

Purpose of the Study:

• To recharacterize clinical isolates of agar-pitting, formate-fumarate-requiring, anaerobic gram-negative bacilli.
• To investigate the clinical significance and antimicrobial susceptibility of Bacteroides ureolyticus and Bacteroides gracilis.

Main Methods:

• Recharacterization of clinical isolates using species descriptions.
• Analysis of clinical data to determine infection types associated with each species.
• Antimicrobial susceptibility testing for B. ureolyticus and B. gracilis.

Main Results:

• Out of 1,341 anaerobic specimens, 7.5% yielded organisms from this group.
• Of 71 isolates studied, 43 were B. ureolyticus, 23 were B. gracilis, and 5 were in the Wolinella-C. concisus group.
• B. gracilis was associated with serious visceral or head and neck infections (83%), while B. ureolyticus was linked to superficial infections (73%).
• B. ureolyticus showed uniform susceptibility to tested antimicrobials.
• B. gracilis exhibited significant resistance to penicillin (33% resistance) and cephalosporins (16–33% resistance).

Conclusions:

• Bacteroides gracilis is an important pathogen associated with severe infections.
• The increasing antibiotic resistance in B. gracilis warrants attention in clinical settings.
• Bacteroides ureolyticus remains susceptible to common antimicrobial agents.