Nosocomial transmission of tuberculosis in HIV/AIDS units in London.

HIV infected individuals are at risk for nosocomially acquired tuberculosis because of increased exposure to tuberculosis in facilities where those with AIDS associated illnesses gather, susceptibility to infection and reinfection, and rapid progression to disease once infection is established.' Restriction fragment length polymorphism (RFLP) analysis of Mycobacterium tuberculosis isolates allows detection of clusters which may be epidemiologically associated.4 6 Among 79 patients in large clusters in New York City, 25 (32%) were shown to be epidemiologically linked, and 19 (76%) of these identified linkages were hospital associated.7 Since 1985, the HIV/AIDS inpatient unit at University College London Hospitals has seen a median number of 94 new patients with AIDS annually. A total of 73 culture confirmed cases of tuberculosis were diagnosed among this population of patients, for a median number annually (with new or prior AIDS diagnoses) since 1990 of 10 (fig). Three clusters of tuberculosis have been identified. In 1992, two patients developed tuberculosis after hospitalisation at the same time as a patient with pulmonary tuberculosis diagnosed at bronchoscopy.8 In 1994, two patients were shown to have similar RFLP pattems and to have shared time on the same ward. In 1996, RFLP analysis was performed on isolates from five patients with tuberculosis who had been hospitalised for overlapping periods; two who had also shared outpatient attendances for nebulised pentamidine treatment had similar RFLP pattems. One of these last two had been working abroad until he shared time with the other in our treatment facilities, making exposure from an unrelated common source less likely. In total, at least seven (17%) of the 41