2000. Related strains of Mycobacterium avium cause disease in children with AIDS and in children with lymphadenitis

Sequence analysis of the ribosomal internal transcribed spacer of 56 Mycobacterium avium complex isolates from pediatric patients with AIDS or lymphadenitis revealed (similar to the situation in adults) that the closely related Mav-B and Mav-A sequevars caused the vast majority of disease. IS1245 restriction fragment±polymorphism analysis and pulsed-®eld gel electrophoresis revealed sets of isolates with closely related patterns among strains from pa-tients in the Boston area and among isolates from Los Angeles and Miami patients. The ®nding of related strains that cause disease in epidemiologically unrelated patients is most consistent with one of two hypotheses: (1) a limited subset of M. avium strains is more virulent and therefore more likely to cause disease in humans, or (2) pathogenic strains are more prevalent in the environment. The Mycobacterium avium complex (MAC) is associated with several disease entities, including skin and soft-tissue infections, pulmonary infection in patients with chronic lung disease, bac-teremia in AIDS patients, and lymphadenitis in children. In AIDS patients, disseminated MAC develops only after sever