A study of HIV-infected persons shows that those with CD4+ lymphocyte counts below 100 cells/mL are found to be at increased risk for pulmonary infections. Some of them have concurrent hepatosplenomegaly and lymphadenopathy, as well as malabsorption with weight loss, night sweats, and fever. Bronchoalveolar lavage specimens examined microscopically show macrophages filled with acid-fast infectious organisms. Which of the following infections have these persons developed?