Are phylogenetic position, virulence, drug susceptibility and in vivo response to treatment in mycobacteria interrelated?

Item does not contain fulltextPhylogenetic analyses on the basis of multiple house-keeping genes and whole genome sequences have offered new insights in the phylogeny of the genus Mycobacterium. This genus yields obligate pathogens, the M. tuberculosis complex and M. leprae, as well as opportunistic pathogens (e.g. M. avium, M. intracellulare, M. kansasii, M. marinum, M. malmoense) and saprophytes (e.g. M. phlei, M. sphagni, M. gordonae). The most virulent mycobacteria, the M. tuberculosis complex, M. leprae and the M. kansasii-M. szulgai-M. marinum-M. ulcerans group are phylogenetically related and infections by these organisms are better treatable than those caused by less virulent and phylogenetically more distantly related Mycobacterium species. The most virulent Mycobacterium species are also characterized by high levels of natural drug susceptibility. In this paper, we review studies of phylogeny, drug susceptibility, and clinical significance to support our hypothesis that drug susceptibility in mycobacteria is acquired and reflects the low level of competition in -and adaptation to- a closer-to-human (environmental) niche. In turn, mycobacteria that inhabit the most competitive environmental niches are the least adapted to humans, thus of low clinical significance, but most tolerant to antibiotics derived from microbes with which they share their habitat, lowering the chances of cure in case of infection.1 juni 201

Drug resistance beyond extensively drugresistant tuberculosis: Individual patient data meta-analysis

The broadest pattern of tuberculosis (TB) drug resistance for which a consensus definition exists is extensively drug-resistant (XDR)-TB. It is not known if additional drug resistance portends worsened patient outcomes. This study compares treatment outcomes of XDR-TB patients with and without additional resistance in order to explore the need for a new definition. Individual patient data on XDR-TB outcomes were included in a meta-analysis comparing outcomes between XDR alone and three nonmutually exclusive XDR-TB patient groups: XDR plus resistance to all the second-line injectables (sli) and capreomycin and kanamycin/amikacin (XDR+2sli) XDR plus resistance to second-line injectables and to more than one group 4 drug, i.e. ethionamide/protionamide, cycloserine/ terizidone or para-aminosalicylic acid (XDR+sliG4) and XDR+sliG4 plus resistance to ethambutol and/or pyrazinamide (XDR+sliG4EZ). Of 405 XDR-TB cases, 301 were XDR alone, 68 XDR+2sli, 48 XDR+sliG4 and 42 XDR+sliG4EZ. In multivariate analysis, the odds of cure were significantly lower in XDR+2sli (adjusted OR 0.4, 95%CI 0.2- 0.8) compared to XDR alone, while odds of failure and death were higher in all XDR patients with additional resistance (adjusted OR 2.6-2.8). Patients with additional resistance beyond XDR-TB showed poorer outcomes. Limitations in availability, accuracy and reproducibility of current drug susceptibility testing methods preclude the adoption of a useful definition beyond the one currently used for XDR-TB. Copyright © ERS 2013.Y