Effect of trimethoprim-sulfamethoxazole prophylaxis in AIDS patients on the formation of the small colony variant phenotype of Staphylococcus aureus.

Emergence of Staphylococcus aureus small colony variants (SCVs) has been associated with antibiotic use, particularly with trimethoprim-sulfamethoxazole (TMP-SMZ). In this study, 634 specimens of 125 patients with AIDS were prospectively screened for S. aureus with normal phenotype and for S. aureus SCVs. Charts of these patients were reviewed for previous prophylaxis with TMP-SMZ often used as long-term pneumocystosis prophylaxis. Thirty-seven patients (29.6%) harbored S. aureus in their anterior nares, three of these patients (8.1%) had S. aureus SCVs. Interestingly, TMP-SMZ does not appear to select for S. aureus SCVs in nasal swabs of these patients.