Microbiology of community-acquired bacterial pneumonia in persons with and at risk for human immunodeficiency virus type 1 infection. Implications for rational empiric antibiotic therapy.

BACKGROUND

Bacterial pneumonia is a very common cause of morbidity and mortality among persons with human immunodeficiency virus; however, the microbiologic characteristics (including antibiotic resistance) of bacterial pathogens causing community-acquired pneumonia in this population have not been well characterized or correlated with potentially predictive clinical presentation characteristics.

METHODS

We conducted a retrospective cohort study of all adults known to have or to be at high risk for human immunodeficiency virus infection and hospitalized at San Francisco (Calif) General Hospital from May 1990 through April 1991, with a hospital discharge diagnosis of community-acquired bacterial pneumonia and for whom a medical records review confirmed that this diagnosis met a uniform case definition.

RESULTS

Two hundred sixteen eligible patients had one or more hospital admissions meeting the case definition. One or more etiologic pathogens were definitively identified in 75% of cases, with Streptococcus pneumoniae, Haemophilus species, Staphylococcus aureus, and gram-negative bacilli most frequently identified. In patients who had a bacteriologic diagnosis made, 18.6%, 6.8%, and 4.3% had pneumonia caused by pathogens resistant to ampicillin sodium, cefuroxime sodium, or trimethoprim-sulfamethoxazole, respectively. One hundred percent of pathogens isolated were susceptible to ceftazidime. Anemia and use of antibacterial medication at the time of hospital admission were the only independent predictors of ampicillin and cefuroxime resistance.

CONCLUSION

Nearly one fifth of human immunodeficiency virus-associated community-acquired bacterial pneumonias requiring hospitalization were caused by ampicillin-resistant pathogens, and presenting clinical characteristics did not consistently define a subset of patients at lower risk for resistance. In the absence of a diagnostic sputum Gram's stain and pending definitive microbiologic diagnosis, initial empiric therapy should be with a second- or third-generation cephalosporin or possibly trimethoprim-sulfamethoxazole.