Isolates of Clostridium perfringens recovered from Costa Rican patients with antibiotic-associated diarrhoea are mostly enterotoxin-negative and susceptible to first-choice antimicrobials.

To assess the prevalence of enterotoxigenic Clostridium perfringens among adults suffering from antibiotic-associated diarrhoea in a Costa Rican hospital, faecal samples were analysed from 104 patients by a cultivation approach. The 29 strains obtained, which accounted for an isolation frequency of 28 %, were genotyped and investigated with regard to their in vitro susceptibility to penicillin, imipenem, cefotaxime, chloramphenicol and metronidazole using an agar-dilution method. A multiplex PCR for detection of the toxins alpha, beta and epsilon predictably classified all faecal isolates as biotype A. An agglutination assay revealed that only one isolate synthesized detectable amounts of enterotoxin (detection rate 3 %). This result was confirmed by a PCR targeting the cpe gene. The spores of the only CPE(+) isolate did not germinate after incubation for 30 min at temperatures above 80 degrees C. Most isolates were susceptible to first-choice antimicrobials. However, unusual MICs for penicillin (16 microg ml(-1)) and metronidazole (512 microg ml(-1)) were detected in one and three isolates, respectively. The low incidence of enterotoxigenic strains suggests that C. perfringens was not a major primary cause of antibiotic-associated diarrhoea in this hospital during the sampling period.