Review Question - QID 106739

This patient is suffering from an intra-abdominal infection. Bacterial infections in the abdomen are typically polymicrobial, with Bacteroides fragilis and Escherichia coli as the two most common organisms.

B. fragilis is an anaerobic Gram-negative rod that is found as part of the normal gastrointestinal tract flora. An abdominal infection with this organism often results from endogenous transmission from the gut due to either abdominal trauma or emergency abdominal surgery. It may be treated with metronidazole, clindamycin, or cefoxitin; however, abscesses should be surgically drained when possible.

Cartwright et al. discuss the evaluation of acute abdominal pain. In a patient without recent surgery or abdominal trauma, an ultrasound is indicated for right upper quadrant pain whereas a CT scan should be performed for left or right lower quadrant pain.

Rotstein et al. postulate that there is a synergistic relationship between B. fragilis and E. coli in abdominal abscesses. Using rat models, the authors showed a reciprocal synergistic relationship between the two organisms. Adding E. coli to a B. fragilis infection increased the size of the abscess as well as the number of B. fragilis organisms. The reverse was also found to be true, with addition of B. fragilis to an E. coli infection resulting in increased abscess weight and numbers of E. coli bacteria.

Illustration A shows a Gram stain of B. fragilis.

Incorrect Answers:
Answers 1,2,4,5: B. fragilis and E. coli are the two most common organisms found in abdominal infections, particularly after preceding abdominal surgery or trauma.