Mycobacterium abscessus virulence traits unraveled by transcriptomic profiling in amoeba and macrophages

Abstract

23Free-living amoebae might represent an evolutionary niche. In order to get more insights into 24 the potential amoebal training ground for Mycobacterium abscessus, we characterized its full 25 transcriptome in amoeba (Ac) and macrophages (Mf), as well as the Mycobacterium chelonae 26 intra-Ac transcriptome for comparison. Up-regulated genes in Ac allowed M. abscessus to 27 resist environmental stress and induce defense mechanisms, as well as showing switch from 28 carbohydrate carbon sources to fatty acid metabolism. Eleven genes implicated in the 29 adaptation to intracellular stress, were mutated, with all but one confirmed to be involved in 30 M. abscessus intra-Mf survival. Cloning two of these genes in M. chelonae increased its intra-31 Mf survival. One mutant was particularly attenuated in Mf that corresponded to the deletion 32 of an Eis N-acetyl transferase protein (MAB_4532c). Taken together, M. abscessus 33 transcriptomes revealed the intracellular lifestyle of the mycobacteria, with Ac largely 34 contributing to the enhancement of M. abscessus intra-Mf survival. such as Mycobacterium avium subsp paratuberculosis and M. avium subsp avium, 48Mycobacterium tuberculosis complex (MTBC) species and Mycobacterium leprae (Ahmed et 49 al., 2007; Stinear et al., 2008). 50Compared to other non-tuberculous mycobacteria (NTM), recovery of M. abscessus from the 51 environment is rare (Thomson et al., 2013). Information from its genome sequence indicates its 52 presence at the interface of soil, vegetation and water, an environment where free-living 53 amoebae (FLA) are commonly found (Ripoll et al., 2009). FLA have been isolated from habitats 54 in common with mycobacteria (Falkinham, 2009; Thomas and McDonnell, 2007) including 55 cold-drinking water systems (Eddyani et al., 2008; Thomas et al., 2006), hot water systems in 56 hospitals and cooling towers (Pagnier et al., 2008). FLA are ubiquitous organisms that feed on 57 bacteria, and these bacteria have likely developed adaptations to the intracellular lifestyle to 58 become amoeba-resistant bacteria (ARB) (Adékambi et al., 2006; Lamrabet et al., 2012). (White et al., 2010), allowing potential evolution toward pathogenicity by the acquisition 61 of virulence genes by horizontal gene transfer (Gutierrez et al., 2005; Ripoll et al., 2009). 62 2006)Finally, amoebae are often considered as an ancestral form of macrophages (Mf) sharing 63 similar cellular structures and biological features (Barker and Brown, 1994; Greub and Raoult, 64 2004; Siddiqui and Khan, 2012). 65 M. abscessus has been shown to be resistant to amoeba phagocytosis and encystment, a 66 property shared with all mycobacteria with the exception of the attenuated M. bovis BCG 67 vaccine strain (Adékambi et al., 2006; Salah et al., 2009; Bakala N'Goma et al., 2015). In 68 addition, co-culture of M. abscessus with Acanthamoeba castellanii (Ac) increases its virulence 69 when aerosolized in mice (Bakala N' Goma et al., 2015) suggesting the existence of an amoebal 70 'training ground' for opportun...

Non-tuberculous mycobacteria and the rise of Mycobacterium abscessus

“…However, this study failed to detect any NTM within free-living amoebae cultivated from hospital water and biofilm samples, suggesting that NTM colonization of cultivable free-living amoebae in these ecosystems may require additional factors that are currently unknown. It is plausible to speculate that survival inside amoebae may be an intermediate life cycle stage that enables M. abscessus to persist in the environment in a protected niche, while also preparing the bacterium for colonization of other hosts 59 . In addition, NTM are highly resistant to many deleterious compounds, such as antibiotics, antiseptics, biocides, sterilizing agents and disinfectants 60 , and thus they are able to survive in hostile environments.…”

“…In addition, M. abscessus encodes two homologues of eis, a gene that promotes intracellular survival in many mycobacteria and Grampositive bacteria: MAB_4124 (also known as eis1) and MAB_4532c (also known as eis2). MAB_4532c greatly enhances intracellular survival of M. abscessus 59 and has been demonstrated to modify kanamycin, hygromycin and amikacin in vitro 140 . Deletion of this gene increases the susceptibility of M. abscessus to these aminoglycosides and to capreomycin 139 .…”

Crystal structure of the aminoglycosides N‐acetyltransferase Eis2 from Mycobacterium abscessus

“…Consistently, a Mabs_eis2 deletion mutant was more susceptible to AG, such as hygromycin B (HYG) and another antibiotic class notably capreomycin than the wild‐type strain . In addition, this mutant showed also a reduced capacity of survival in macrophages as compared to its parental or complemented counterparts . Expression of Mabs_eis2 was shown to be upregulated a 100 times upon exposure of Mabs culture to AMK, via a mechanism implicating the master transcription regulator WhiB7, known to control the expression of many genes involved in drug resistance pathways .…”

MtrAB two-component system is crucial for the intrinsic resistance and virulence ofMycobacterium abscessus

“…The virulence traits of Mab render it pathogenic in fragile hosts with structural lung disease. The interactions between the robust mycobacterial lipid-rich sturdy cell envelope and host immune cells enables Mab to survive within the host's challenging internal environment [34][35][36]. Several identified virulence factors (VFs) are associated with cell envelope.…”