Evidence of nosocomial transmission of tuberculosis among AIDS patients by DNA fingerprinting.

DNA restriction fragment length polymorphism (RFLP) analysis was performed on Mycobacterium tuberculosis isolates from patients in the human immunodeficiency virus (HIV) Unit of a community hospital. It was found that M. tuberculosis isolates from two patients with AIDS shared an identical RFLP pattern. Such a fingerprint was not found in M. tuberculosis isolates from any of 40 HIV-negative patients hospitalized in different Units over the same period, assumed as representative of the strains present in the community, thus ruling out that the isolates from the two AIDS patients might match because only a few strains were present in the community. Clinical records of the two AIDS patients showed an 8-day concomitant hospitalization period in the same ward during which one of the two patients showed active tuberculosis; the second patient developed active tuberculosis less than two months later. These findings strongly support the possibility of nosocomial transmission of tuberculosis.