Deletion of a dehydratase important for intracellular growth and cording renders roughMycobacterium abscessusavirulent

Abstract

Mycobacterium abscessus(Mabs) is a rapidly growingMycobacteriumand an emerging pathogen in humans. Transitioning from a smooth (S) high-glycopeptidolipid (GPL) producer to a rough (R) low-GPL producer is associated with increased virulence in zebrafish, which involves the formation of massive serpentine cords, abscesses, and rapid larval death. Generating a cord-deficientMabsmutant would allow us to address the contribution of cording in the physiopathological signs of the R variant. Herein, a deletion mutant ofMAB_4780, encoding a dehydratase, distinct from the β-hydroxyacyl-ACP dehydratase HadABC complex, was constructed in the R morphotype. This mutant exhibited an alteration of the mycolic acid composition and a pronounced defect in cording. This correlated with an extremely attenuated phenotype not only in wild-type but also in immunocompromised zebrafish embryos lacking either macrophages or neutrophils. The abolition of granuloma formation in embryos infected with the dehydratase mutant was associated with a failure to replicate in macrophages, presumably due to limited inhibition of the phagolysosomal fusion. Overall, these results indicate that MAB_4780 is required forMabsto successfully establish acute and lethal infections. Therefore, targeting MAB_4780 may represent an attractive antivirulence strategy to controlMabsinfections, refractory to most standard chemotherapeutic interventions. The combination of a dehydratase assay with a high-resolution crystal structure of MAB_4780 opens the way to identify such specific inhibitors.