At least three studies in sub-Saharan Africa have demonstrated a decrease in morbidity or mortality among HIV-infected adults who took daily cotrimoxazole (trimethoprim sulfamethoxazole) [CTX] prophylaxis. Because of the demonstrated beneficial effect, high tolerability and low cost of CTX, the United Nations Programme on HIV/AIDS (UNAIDS) recommends that HIV-infected persons with symptomatic HIV or depressed CD4 counts receive daily CTX. The effect of this recommendation on subsequent development of antimicrobial resistance to antifolates among important pathogens needs to be evaluated. The investigators measured the change in the prevalence of markers of antifolate resistance among P. falciparum, and the change in the prevalence of CTX resistance among S. pneumoniae, and E. coli in HIV-infected individuals receiving CTX daily prophylaxis. In addition, the investigators measured the change in the prevalence of naso-pharyngeal or oro-pharyngeal carriage of CTX resistant S. pneumoniae among children living in households where an HIV-infected adult was receiving CTX daily prophylaxis.