Mycobacterium llatzerense, a waterborne Mycobacterium, that resists phagocytosis by Acanthamoeba castellanii

Abstract

Nontuberculous mycobacteria (NTM) are environmental bacteria increasingly associated to public health problems. In water systems, free-living amoebae (FLA) feed on bacteria by phagocytosis, but several bacteria, including many NTM, are resistant to this predation. Thus, FLA can be seen as a training ground for pathogenic bacteria. Mycobacterium llatzerense was previously described as frequently associated with FLA in a drinking water network. The present study aimed to characterize the interactions between M. llatzerense and FLA. M. llatzerense was internalised by phagocytosis and featured lipid inclusions, suggesting a subversion of host resources. Moreover, M. llatzerense survived and even multiplied in presence of A. castellanii. Using a genomic-based comparative approach, twelve genes involved in phagocytosis interference, described in M. tuberculosis, were identified in the M. llatzerense genome sequenced in this study. Transcriptomic analyses showed that ten genes were significantly upregulated during the first hours of the infection, which could partly explain M. llatzerense resistance. Additionally, M. llatzerense was shown to actively inhibit phagosome acidification. In conclusion, M. llatzerense presents a high degree of resistance to phagocytosis, likely explaining its frequent occurrence within FLA in drinking water networks. It underscores that NTM should be carefully monitored in water networks to prevent human health concerns.

Environmental Mycobacterium avium subsp. paratuberculosis Hosted by Free-Living Amoebae

“…This suggests that Map could block, to a certain extent, the normal acidification process of A. castellanii phagosomes. Inhibition of phagosomal acidification has been observed with other Mycobacterium species both in amoebae and macrophages (Kuehnel et al, 2001 ; Rohde et al, 2007 ; Delafont et al, 2017 ). Although much of the cell biology has been done on mycobacteria-macrophage interactions, further investigations would be required to better understand the fate of Map after its internalization in amoeba.…”

“…These results suggest that interactions between these two types of microorganisms could very likely happen in the environment. This stability could indeed favor Map resilience in the environment, providing a shelter against harsh conditions, as well as a potential substrate source for mycobacterial multiplication (Caire-Brändli et al, 2014 ; Barisch et al, 2015 ; Delafont et al, 2017 ).…”

Human Neutrophil Granule Exocytosis in Response to Mycobacterium smegmatis

“…This could reflect a survival mechanism used in soil and water environments where these bacteria normally reside. In water, free-living amoeba feed on bacteria by phagocytosis, but many environmental mycobacteria resist this predation by blocking uptake by protists [39,40]. Opsonization with human serum prior to neutrophils interaction appears to circumvent these strategies.…”

Disinfectant residuals in drinking water systems select for mycobacterial populations with intrinsic antimicrobial resistance

“…In two of these bins, RbpA (rifamycin resistance) and mtrA (macrolife and penam resistance) co-occur. M. llatzarense has been isolated from DWDS and is described as a NTM that resists amoebal phagocytosis and survives disinfection 74,75 . Similarly, Bin3 associated with the M. chelonae - absceccus complex also demonstrated the presence of gene conferring rifamycin resistance.…”