In vitro susceptibility of Clostridium difficile isolates from patients with antibiotic-associated diarrhea or colitis

Abstract

In vitro susceptibility tests were performed on 84 strains of Clostridium difficile to 11 antimicrobial agents. All isolates were from the stools of patients with antibiotic-associated diarrhea or colitis in which there was a cytopathic toxin that was neutralized by Clostridium sordellii antitoxin. Over 95% of the strains were susceptible to vancomycin, penicillin G, ampicillin, and metronidazole at concentrations of 4 microgram/ml. Susceptibility to clindamycin was variable; 60% of the strains were susceptible at 1 microgram/ml, and 9% were resistant at 128 microgram/ml. Studies of individual isolates showed that a major portion of the strains were relatively susceptible to the antimicrobial agent implicated in causing the disease.