In Part A, patients receive sulfamethoxazole-trimethoprim (SMX/TMP) alone for 2 weeks, then in combination with fluconazole, rifabutin, or both drugs, each over 2-week periods in a randomly assigned order. Patients in Part B receive the same regimens except with clarithromycin substituted for rifabutin. In Part C, patients receive dapsone alone for 2 weeks, then in combination with fluconazole, rifabutin, or both drugs in the same manner as in Part A. Part D patients receive the same regimen as those in Part C, except with clarithromycin substituted for rifabutin. Patients are followed every 2 weeks.