Streptococcus pneumoniae colonization, bacteremia, and immune response among persons with human immunodeficiency virus infection.

Although invasive pneumococcal infections are common among men infected with human immunodeficiency virus (HIV), the prevalence of pharyngeal colonization with Streptococcus pneumoniae was not significantly different among HIV-infected patients (8 [14%] of 56) and HIV-seronegative men (9 [9%] of 99) attending a sexually transmitted disease clinic. Sixteen HIV-infected men (mean CD4+ T cell count, 132 +/- 37/microL) developed pneumococcal bacteremia, accounting for 13.6% of 117 total cases and 42% of 38 cases in men 16-55 years old. Serum killing activity, a measure of functional humoral response to S. pneumoniae, was lower in 4 (67%) of 6 acute sera and 6 (54%) of 11 convalescent sera from bacteremic HIV-infected patients when compared with baseline sera of 7 HIV-seronegative healthy subjects. These findings suggest that the high rates of pneumococcal bacteremia among HIV-infected patients may be associated with low numbers of CD4+ T cells and impaired humoral responses to S. pneumoniae rather than to increased exposure to the organism.