HETEROGENEITY AND CLONALITY AMONG ISOLATES OF MYCOBACTERIUM-KANSASII - IMPLICATIONS FOR EPIDEMIOLOGIC AND PATHOGENICITY STUDIES

The reservoir and transmission route of Mycobacterium kansasii are lar gely unknown. In addition, culturing of M. kansasii from human sources is not proof of disease because it may represent colonization rather than infection. Unfortunately, investigation of the epidemiology and p athogenicity of M. kansasii is complicated by evidence of heterogeneit y within the species. A comprehensive study by detailed genotypic anal ysis of a large collection of M, kansasii isolates (n = 276) from vari ous geographical sources within Europe was conducted. Five defined sub types of M. kansasii were identified; of these subtypes, type I repres ents the most common isolate from humans. Although phylogenetic analys is confirmed its relationship to the other M, kansasii types, signific ant sequence divergence was found at the 16S-23S intergenic spacer. An alysis of the chromosomal polymorphism of type I demonstrated a marked clonal structure for this particular organism. Because M. kansasii is becoming a significant pathogen among immunodeficient hosts, future e pidemiological and pathogenicity studies should take into consideratio n both the heterogeneity,within the species and the apparent clonality of the most prevalent M, kansasii isolates infecting humans.