The risks and benefits of childhood bacille Calmette-Guerin immunization among adults with AIDS

Objective: To define the risks of disseminated bacille Calmette-Guerin (BCG) or disseminated Mycobacterium tuberculosis in adults with AIDS who were immunized with BCG in childhood. Design: HIV-infected patients with CD4 < 200 x 106/l were enrolled from five study sites (New Hampshire, Boston, Finland, Trinidad and Kenya). Prior BCG immunization was determined and blood cultures for mycobacteria were obtained at study entry and at 6 months. Acid-fast bacilli were identified as Mycobacterium tuberculosis complex (MTBC) using DNA probes. MTBC isolates were then typed by both IS6110 restriction fragment length polymorphism and polymerase chain reaction/restriction enzyme analysis. Setting: Most patients in New Hampshire and Finland were outpatients; most patients in Trinidad were inpatients with terminal illness; and most patients in Kenya were outpatients, although 44 were inpatients with terminal illness. Participants: A total of 566 patients were enrolled, including 155 with childhood BCG immunization; 318 patients had a single study visit and culture, and 248 patients had two study visits and cultures. Main outcome measures: Isolation and identification of mycobacteria from blood cultures. Results: Blood cultures were positive for MTBC in 21 patients; none were positive for M. bovis BCG, and 21 were M. tuberculosis-positive. In Trinidad, seven (87%) out of eight isolates of M. tuberculosis were indistinguishable by IS6110 typing; BCG immunization was associated with a decreased risk of bacteremic infection with M. tuberculosis (P = 0.05). Conclusions: The risk of disseminated BCG among adult AIDS patients with childhood BCG immunization is very low. Childhood BCG immunization is associated with protection against bacteremia with M. tuberculosis among adults with advanced AIDS in Trinidad.