Comparison of enterotoxin production, cytotoxin production, serogrouping, and antimicrobial susceptibilities of Clostridium difficile strains isolated from AIDS and human immunodeficiency virus-negative patients.

We analyzed and compared Clostridium difficile strains isolated from diarrheic stools of 49 human immunodeficiency virus (HIV)-negative and 50 AIDS patients. Our results suggest that distribution patterns of serogroups are different in these two populations. Serogroup C (which has been previously reported to be very resistant to antimicrobial agents) represents 66.0 and 18.4% of the isolates from AIDS and HIV-negative patients, respectively (P < 0.001); the selection of serogroup C could be explained by multiple antibiotic pressure to which AIDS patients have been subjected.