There are limited data on the incidence of bacterial infections during the course of HIV infection. The available data suggest that the incidence of bacterial infections varies by stage of disease and risk group. Among outpatients followed in New York City through 1989, injection drug users (IDU) were more likely to have bacterial pneumonia than homosexual men. Whites were less likely to have salmonella sepsis than non-Haitian blacks, and no differences were noted by gender. Episodes of bacterial pneumonia were recorded for 16% of the nearly 3000 patient records reviewed during a 2-year period in this study.⁽²⁸⁾

In a large cohort study of injection drug users in New York, the incidence of pneumonia and sepsis among those with HIV infection was 8.0 episodes per 100 person-years.⁽⁷⁾ Incidence rates for bacterial infections were highest in those with CD4 counts of <200/mm³. A higher rate of death from bacterial infections was also observed among drug users with HIV in this study compared to noninfected IDU. An increase in the rate of bacterial pneumonia was found among HIV-infected IDU followed prospectively in Amsterdam over a 3-year period.⁽²⁹⁾ The incidence of bacterial pneumonia rose from 0.1 episode per person-year (10 per 100 person-years) in 1986 to 0.29 episodes per person-year in 1989. Drug users co-infected with HIV were four times more likely to develop bacterial pneumonia than seronegative IDU; however, in contrast to the New York study,⁽⁷⁾ no increase in non-AIDS mortality was noted in this cohort.⁽²⁹⁾

During an 18-month follow-up period in a prospective study of the pulmonary complications of AIDS (PACS), upper respiratory infection was the most common infection (33%), followed by acute bronchitis (16%), acute sinusitis (5.3%), and bacterial pneumonia (4.8%). Risk factors for developing bacterial pneumonia were an entry CD4 count of <250/mm³ and a history of injecting drugs. The rate of bacterial pneumonia in HIV-infected subjects in this study was nearly eightfold higher than in controls matched by risk behavior.⁽³⁰⁾

In another study, nonopportunistic bacterial infections occurred in almost a third of 788 consecutive hospitalized HIV-infected patients in a 7-year period.⁽³¹⁾ Sepsis/Bacteremia was the most common presentation (33%), followed by respiratory tract (24%) and genitourinary tract infections (21%). Morbidity from bacterial infections increased with advancing stage of HIV infection but did not vary by age, sex, or risk behavior in this study. Gram-positive organisms accounted for half of the infections and tended to be more common in cases of bacteremia and sepsis.

There are extremely limited data available to determine whether neutropenia increases the risk of bacterial infections in HIV-infected patients. In one small study, 29 neutropenic AIDS patients were matched by age, sex, and CD4 count with nonneutropenic AIDS patients.⁽³²⁾ Patients with neutropenia were statistically significantly more likely to develop bacteremia than controls; there were no differences in the presence of intravenous catheters or use of antiretroviral therapy between groups. With the availability of growth factors that increase the circualting neutrophil count, prospective data is urgently needed to determine the role of neutropenia in the development of bacterial infections in AIDS.