Deletion of a dehydratase important for intracellular growth and cording renders rough Mycobacterium abscessus avirulent

Abstract

Mycobacterium abscessus (Mabs) is a rapidly growing Mycobacterium and 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-deficient Mabs mutant would allow us to address the contribution of cording in the physiopathological signs of the R variant. Herein, a deletion mutant of MAB_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 for Mabs to successfully establish acute and lethal infections. Therefore, targeting MAB_4780 may represent an attractive antivirulence strategy to control Mabs infections, refractory to most standard chemotherapeutic interventions. The combination of a dehydratase assay with a highresolution crystal structure of MAB_4780 opens the way to identify such specific inhibitors.M. abscessus | zebrafish | cording | dehydratase | virulence

Resistance to Thiacetazone Derivatives Active against Mycobacterium abscessus Involves Mutations in the MmpL5 Transcriptional Repressor MAB_4384

“…Since previous TAC analogues were found to be more efficient against M. avium (16) and M. tuberculosis (19), we were prompted to address whether TAC analogues also exhibit potent activity against M. abscessus, notorious for being the most drug-resistant mycobacterial species (21), despite being refractory to TAC inhibition in liquid cultures (MIC of Ͼ100 g/ml) (18). As shown in Table 1, the compounds exhibited a broad range of activity against the rough (R) variant of M. abscessus CIP104536, from active compounds (Ͻ10 g/ml) to derivatives exhibiting only modest (Ͻ50 g/ml) or very poor activity (Ն100 g/ml).…”

“…Upon activation, TAC has recently been shown to bind to the HadA component of the HadABC dehydratase complex, leading to inhibition of mycolic acid biosynthesis (15). Interestingly, we and others have reported that NTM such as Mycobacterium avium (16), Mycobacterium smegmatis (17), and M. abscessus (18) are naturally resistant to TAC. However, a TAC analogue, SRI-224, was previously tested against M. avium and found to be more effective than TAC in vitro as well as in mice (16) and subsequently shown to be very active against M. tuberculosis (19).…”

MAB_3551c encodes the primary triacylglycerol synthase involved in lipid accumulation in Mycobacterium abscessus

“…Indeed, although representing an emerging human pathogen involved in pulmonary and cutaneo‐mucous infections, M. abscessus is endowed with metabolic pathways typically found in environmental microorganisms that are in contact with soil, plants and aquatic environments (Ripoll et al ., ) where free‐living amoebae are present. We and others have recently shown that M. abscessus can survive in amoebae (Drancourt, ; Bakala N'Goma et al ., ; Halloum et al ., ). Interestingly, amoebae such as Dictyostelium have been shown to build up their own lipid bodies when presented with palmitic acid (Du et al ., ).…”

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

“…Additionally, a Mabs R mutant defective in cording showed severely impaired replication in both macrophages and amoebae, presumably due to limited inhibition of the phagolysosomal fusion. These studies emphasize the usefulness of amoebae as a host model to identify and study determinants important in sustaining Mabs virulence (Halloum et al, 2016). Despite the failure of isolating Mabs from environmental sources, studies with Acanthamoeba suggest that Mabs has evolved in close contact with environmental protozoa and support the view that amoebae contribute in shaping Mabs virulence (Bakala N'Goma et al, 2015; Le Moigne et al, 2016).…”

“…This has led to the recent identification of the MAB_4780 gene encoding a dehydratase. Disruption of this gene in Mabs R was associated with the lack of granuloma formation in embryos and a highly attenuated phenotype in wild-type and in embryos lacking either macrophages or neutrophils (Halloum et al, 2016). Overall, work using the zebrafish model confirmed the crucial role of MAB_4780 for Mabs cording to successfully establish acute and lethal infections.…”