Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are not commonly recognized in healthy patients without predisposing risk. We performed a retrospective study of patients hospitalized with community-acquired MRSA infections from 1992 to 1996 in Honolulu to determine if community-acquired MRSA infections occurred in patients without known risk. Patients hospitalized within the previous 6 months or transferred from other hospitals or nursing homes were excluded. Epidemiological and clinical data were obtained from an inpatient chart review. Ten (71%) of 14 patients with community-acquired MRSA infection had no discernible characteristics of MRSA infections. Thirteen (93%) patients had skin or soft-tissue infections and one patient had MRSA pneumonia. Isolates from patients with MRSA infection were more likely to be susceptible to ciprofloxacin (P = .05), clindamycin (P = .03), and erythromycin (P = .01) than were those from MRSA-colonized patients. In our population, the majority of community-acquired MRSA infections occurred in previously healthy individuals without characteristics suggestive of MRSA transmission.

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Virulent toxigenic and avirulent non-toxigenic strains of Clostridium difficile gave a positive result in the latex agglutination test (LAT) for C difficile toxin A (D-1). Similar concentrations of latex agglutinating antigen were produced by these strains in vivo. Positive reactions were also given by C sporogenes, proteolytic C botulinum Types A, B, and A/F, and Bacteroides assaccharolyticus. The latex agglutinating antigen was denatured by boiling for 10 minutes, but not by heating at 56 degrees C for 30 minutes. The reaction was abolished by incubation of test material with crude C difficile antitoxin but not with other clostridial antitoxins or specific antitoxin to C difficile toxin A. The latex agglutinating antigen present in C difficile eluted between 0.39% and 0.47% M sodium chloride, and that produced by the other clostridia, between 0.35% and 0.43% M sodium chloride by fast protein liquid chromatography. The latex agglutinating antigen of C difficile was neither cytotoxic nor mouse lethal and was distinct from toxin A and toxin B. In the analysis of faecal specimens from patients with diarrhoea the latex agglutination test correlated better with the presence of C difficile than with toxin B and detected both toxigenic and non-toxigenic strains. The latex agglutination test should only be used in the laboratory as an alternative to culture for C difficile and not as a method for the detection of C difficile toxins.

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