Isolation rates and toxigenic potential of Clostridium difficile isolates from various patient populations.

Stool specimens in various patient populations were examined to determine isolation rates of Clostridium difficile and the frequency with which this organism produces a cytopathic toxin in vitro. Clostridium difficile was isolated from 13 of 45 healthy neonates who had never received antimicrobials and the cytotoxin was detected in 12. With 23 healthy children aged 4 to 24 mo the organism was recovered from 2 children and the cytotoxin was detected in 1. Neither the organism nor the cytotoxin was found in specimens from healthy adults who denied antimicrobial usage during the prior 4 wk. Clostridium difficile was recovered from 12 of 56 adults receiving antimicrobials without diarrhea, but only one specimen yielded the cytotoxin. Both the cytotoxin and the organism were found in stools from most patients with antibiotic-associated colitis. Concentrations of Clostridium difficile, when present, were similar in all patient populations. Broth cultures of 165 isolates of Clostridium difficile showed all strains, but two produced the cytotoxin in vitro. However, the concentration of the toxin was substantially higher with strains recovered from patients with positive toxin assays. These observations indicate that neonates are often asymptomatic carriers of both Clostridium difficile and its cytotoxin. In adults, gastrointestinal symptoms correlated best with results of tissue culture assays and with toxigenic potential of the strains isolated.