Persistence of Pneumocystis carinii in patients with AIDS receiving chemoprophylaxis

Pneumocystis carinii organisms have been shown to persist throughout therapy in the majority of patients with Pneumocystis carinii pneumonia (PCP). This study evaluated the relationship between persistence of organisms and recurrence of disease, and the effect of chemoprophylaxis on bronchoalveolar lavage specimens. Seven patients receiving PCP chemoprophylaxis underwent serial bronchoalveolar lavage (BAL) examinations at 1, 4, and 7 mo after recovery from a first episode of PCP. Specimens were examined for persistent organisms with Gomori's methenamine silver stain and immunofluorescent antibody staining. There were no persistent organisms 1 mo after completion of antimicrobial treatment in six of the seven patients. The one patient with persistent organisms demonstrated clearance of organisms by 4 mo and had no recurrence of PCP. One patient had a recurrence of PCP at 4 mo, after a negative 1-mo BAL. We conclude that a positive BAL result by silver stain or immunofluorescent antibody staining more than a month after ending treatment may indicate clinical recurrence of PCP and not just persistence of nonpathologic cysts. These findings suggest that recurrences of PCP are more likely due to new infection than to relapse of prior disease.