Genomic and Phenotypic Variability of Mycobaterium avium Subspecies

Abstract

Introduction: Mycobacterium avium complex consists of M. intracellulare and the subspecies of M. avium subsp. avium, M. avium subsp. paratuberculosis and M. avium subsp. hominissuis. Despite their taxonomic relationship, these subspecies are organisms with distinct phenotypes, ranging from environmental bacteria that cause infections in immunocompromised hosts to pathogens targeting birds and ruminants. The reasons for the variable pathogenicity and host range of M. avium subspecies are not known. We hypothesize that genotypic differences between M. avium subsp. avium and M. avium subsp. paraturberculosis can explain different pathogenic outcomes. Methods: We used tri-genomic comparisons to look for DNA fragments unique to each subspecies. We also used an acute model of mouse infection to determine different phenotypic outcomes in response to infection with different Mycobacterium subspecies. results: Through tri-genomic comparisons we identified genetic regions of interest that may contain genes to explain phenotypic or pathogenic differences among subspecies. In an 8 week course infection, mice infected with M. avium subspecies avium had the highest bacterial burden in their spleens and livers. at the same time, mice infected with M. avium subspecies paraturberculosis had the lowest bacterial burden. discussion: Differences in the genomic sequences of the M. avium subspecies suggests that these sequences encode pathogenic factors. Consequently, this study shows that the sequencing of M. avium subspecies genomes can be useful for predicting and explaining variation in pathogenesis.