Impact of trimethoprim-sulfamethoxazole prophylaxis on etiology and susceptibilities of pathogens causing human immunodeficiency virus-associated bacteremia.

The impact of chronic prophylactic administration of trimethoprim-sulfamethoxazole (SXT) on the ecology and the antimicrobial susceptibilities of bloodstream pathogens in human immunodeficiency virus (HIV)-infected patients was studied using a retrospective chart review. Eighty-nine patients with advanced HIV infection developed 124 episodes of bacteremia with 156 pathogenic isolates. Staphylococcus aureus and Enterobacteriaceae tended to be less common among patients receiving SXT. Isolates from patients receiving SXT were likelier (75%) to be resistant to 20 microg of SXT/ml than those from patients not receiving SXT (33%) (P < 0.001).