Trimethoprim-sulfamethoxazole prophylaxis and antibiotic nonsusceptibility in invasive pneumococcal disease.

Among 5,043 invasive pneumococcal disease (IPD) isolates identified through South African national surveillance from 2003 to 2007, we estimated the effect of trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis on antimicrobial resistance. Patients on TMP-SMX prophylaxis were more likely to have a pneumococcal isolate nonsusceptible to TMP-SMX, penicillin, and rifampin. TMP-SMX nonsusceptibility was associated with nonsusceptibility to penicillin, erythromycin, and rifampin and multidrug resistance. This study informs empirical treatment of suspected IPD in patients with a history of TMP-SMX use.