Predominant Staphylococcus aureus isolated from antibiotic-associated diarrhea is clinically relevant and produces enterotoxin A and the bicomponent toxin LukE-LukD

Staphylococcus aureus was isolated as the predominant or only isolate from cultures of stools of 60 patients over 2 Sears in a university hospital, le ading to the collection of 114 isolates. Diarrhea was observed in 90% of th e patients. Ninety-eight percent of the patients had received antibiotics i n the month before the diarrhea. Ninety-two percent of the S. aureus isolat es were methicillin resistant. S, aureus was encountered with antibiotic-as sociated diarrhea among 47 quite elderly patients affected or not affected by a gastrointestinal disease. Among the antimicrobial treatments, cessatio n of the previous therapy when possible or rapid application of oral vancom ycin therapy was the most appropriate. Analysis of total DNA by pulsed-fiel d gel electrophoresis revealed 27 different SmaI pulsotypes distributed in 15 clusters. The pulsotypes never differed for related isolates from a sing le patient, even if they originated from patients with bacteremia. S, aureu s was not isolated as the predominant isolate in cultures of stools of 57 p atients who received an antimicrobial treatment for more than 5 days withou t diarrhea, Occurence of production of both enterotoxin A and the bicompone nt leucotoxin LukE-LukD by the S, aureus isolates was significantly differe nt from that by random Isolates. The results strongly suggest that when pre dominant in stool samples, S, aureus should be considered a possible etiolo gic agent for some cases of antibiotic-associated diarrhea.