Mycobacterium avium in the Postgenomic Era

Abstract

SUMMARY The past several years have witnessed an upsurge of genomic data pertaining to the Mycobacterium avium complex (MAC). Despite clear advances, problems with the detection of MAC persist, spanning the tests that can be used, samples required for their validation, and the use of appropriate nomenclature. Additionally, the amount of genomic variability documented to date greatly outstrips the functional understanding of epidemiologically different subsets of the organism. In this review, we discuss how postgenomic insights into the MAC have helped to clarify the relationships between MAC organisms, highlighting the distinction between environmental and pathogenic subsets of M. avium. We discuss the availability of various genetic targets for accurate classification of organisms and how these results provide a framework for future studies of MAC variability. The results of postgenomic M. avium study provide optimism that a functional understanding of these organisms will soon emerge, with genomically defined subsets that are epidemiologically distinct and possess different survival mechanisms for their various niches. Although the status quo has largely been to study different M. avium subsets in isolation, it is expected that attention to the similarities and differences between M. avium organisms will provide greater insight into their fundamental differences, including their propensity to cause disease.

rpoB sequence-based identification of Mycobacterium avium complex species

“…avium/silvaticum and M. avium subsp. paratuberculosis organisms (Turenne et al, 2007). Two isolates identified as M. chimaera represent the first isolates of this novel species to be reported in addition to the initial M. chimaera report (Tortoli et al, 2004).…”

“…avium/silvaticum and M. avium subsp. paratuberculosis being two independent, specialized clones (Turenne et al, 2007). Mycobacterium intracellulare has been isolated more frequently in HIVnegative patients (Devallois et al, 1996).…”

“…The Mycobacterium avium complex (MAC) comprises slowly growing mycobacteria (Tortoli et al, 1999;Turenne et al, 2007;Yajko et al, 1995) responsible for opportunistic infections and zoonoses (Karakousis et al, 2004;Lauzi et al, 2000). M. avium has been further divided into M. avium subsp.…”

Defining mycobacteria: Shared and specific genome features for different lifestyles

“…Considering that MAC organisms are found to reside in both environmental and host associated niches, Turenne et al [76] have recommended that MAC be considered as a 'microcosm' of mycobacteria with distinct genomic identities. It is expected that additional sequencing of representative genomes from different host niches will clarify some of the existing confusion in taxonomy.…”

“…• Turenne et al [76] have pointed out that although M. avium subsp. avium are popularly referred to as environmental species, strains found in birds are not found in human MAC infections and environmental sources [71].…”