Which statement is true of Bacteroides fragilis?

• A. Lipase and lecithinase positive
• B. Anaerobic gram-positive bacillus
• C. Commonly associated with intra-abdominal infections
• D. Among the most antimicrobial-sensitive anaerobic bacteria

Answer: (C)

Bacteroides fragilis is an anaerobic, non-spore-forming Gram-negative bacillus that is part of the normal gut flora. When the GI tract is breached, it becomes a frequent cause of infection, especially in the abdomen, where it can drive abscess formation and peritonitis. This organism is notable for beta-lactamase production, which makes it resistant to many penicillins and some other beta-lactams, so it is not among the most antimicrobial-sensitive anaerobes; effective treatments often include metronidazole or carbapenems, sometimes with beta-lactamase inhibitors. Its virulence is aided by a polysaccharide capsule that helps it evade host defenses and form abscesses, but lipase and lecithinase are not typical virulence factors for this species. Therefore, the statement that it is commonly associated with intra-abdominal infections is true and best reflects its clinical role.