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

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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.

No MeSH data available.


Related in: MedlinePlus

M. llatzerense EDP_4 is efficiently internalised by A. castellanii.Transmission electron microscopy of A. castellanii infected by M. llatzerense EDP_4 at a MOI of 1, at 4 h (A,B) 24 h (C) and 72 h (D) post infection. Bars represent 1 μm. Lipid bodies are indicated by asterisks on micrographs.
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f3: M. llatzerense EDP_4 is efficiently internalised by A. castellanii.Transmission electron microscopy of A. castellanii infected by M. llatzerense EDP_4 at a MOI of 1, at 4 h (A,B) 24 h (C) and 72 h (D) post infection. Bars represent 1 μm. Lipid bodies are indicated by asterisks on micrographs.

Mentions: To gain insights into the interaction between M. llatzerense and A. castellanii, infected amoeba cultures were observed using transmission electron microscopy (TEM). M. llatzerense bacilli were mostly found intracellularly in vacuoles, which suggested an active internalisation process (Fig. 3). Starting from 4 h post infection, intracellular M. llatzerense harboured numerous inclusions into their cytoplasm, which were more frequently observed after 24 h and 72 h (Fig. 3B–D respectively). These inclusions were further confirmed to be of lipidic nature (supplementary Figure 1). In comparison, non-internalised bacilli did not harbour such inclusions (Fig. 3A). Lipid droplets from the host were also observed in the vicinity of M. llatzerense-containing vacuoles (Fig. 3C). Internalisation of bacteria by phagocytic cells such as FLA is mostly mediated by phagocytosis. Indeed, this was confirmed for M. llatzerense, as its internalisation was abrogated by the treatment of A. castellanii with cytochalasin D, a potent inhibitor of actin polymerisation (Fig. 4). Thus, it was shown that M. llatzerense internalisation by A. castellanii is indeed mediated by phagocytosis. This NTM species was able to persist intracellulary for at least 96 h.


Mycobacterium llatzerense , a waterborne Mycobacterium , that resists phagocytosis by Acanthamoeba castellanii
M. llatzerense EDP_4 is efficiently internalised by A. castellanii.Transmission electron microscopy of A. castellanii infected by M. llatzerense EDP_4 at a MOI of 1, at 4 h (A,B) 24 h (C) and 72 h (D) post infection. Bars represent 1 μm. Lipid bodies are indicated by asterisks on micrographs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385496&req=5

f3: M. llatzerense EDP_4 is efficiently internalised by A. castellanii.Transmission electron microscopy of A. castellanii infected by M. llatzerense EDP_4 at a MOI of 1, at 4 h (A,B) 24 h (C) and 72 h (D) post infection. Bars represent 1 μm. Lipid bodies are indicated by asterisks on micrographs.
Mentions: To gain insights into the interaction between M. llatzerense and A. castellanii, infected amoeba cultures were observed using transmission electron microscopy (TEM). M. llatzerense bacilli were mostly found intracellularly in vacuoles, which suggested an active internalisation process (Fig. 3). Starting from 4 h post infection, intracellular M. llatzerense harboured numerous inclusions into their cytoplasm, which were more frequently observed after 24 h and 72 h (Fig. 3B–D respectively). These inclusions were further confirmed to be of lipidic nature (supplementary Figure 1). In comparison, non-internalised bacilli did not harbour such inclusions (Fig. 3A). Lipid droplets from the host were also observed in the vicinity of M. llatzerense-containing vacuoles (Fig. 3C). Internalisation of bacteria by phagocytic cells such as FLA is mostly mediated by phagocytosis. Indeed, this was confirmed for M. llatzerense, as its internalisation was abrogated by the treatment of A. castellanii with cytochalasin D, a potent inhibitor of actin polymerisation (Fig. 4). Thus, it was shown that M. llatzerense internalisation by A. castellanii is indeed mediated by phagocytosis. This NTM species was able to persist intracellulary for at least 96 h.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus