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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.


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CFU count of M. llatzerense after infection of A. castellanii pre-treated or not with rapamycin.(A). Colocalisation of live or heat-killed M. llatzerense within intracellular acidic compartments labelled with pHrodo (B). Statistical tests were performed using unpaired t-tests (P < 0.001***).
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f6: CFU count of M. llatzerense after infection of A. castellanii pre-treated or not with rapamycin.(A). Colocalisation of live or heat-killed M. llatzerense within intracellular acidic compartments labelled with pHrodo (B). Statistical tests were performed using unpaired t-tests (P < 0.001***).

Mentions: In order to strengthen the results depicting significant changes of M. llatzerense gene expression during the early infection stage, we aimed to characterise its intracellular survival. Following internalisation, the resistance of M. llatzerense to A. castellanii degradation was assessed, by stimulating the autophagic machinery using rapamycin. Autophagy was described as a major pathway for blocking tuberculous mycobacteria proliferation in host cells, as its activation greatly affects mycobacteria survival4647. M. llatzerense survival was monitored for up to four hours after rapamycin treatment. Bacterial viability significantly decreased at 0, 1 and 4 hours after rapamycin treatment, as half of the bacilli survived compared to control condition (Fig. 6A). While significant, even in condition where bacterial degradation through phagocytosis and autophagy were strongly stimulated, we did not reach M. llatzerense total elimination, confirming its strong ability to resist A. castellanii degradation.


Mycobacterium llatzerense , a waterborne Mycobacterium , that resists phagocytosis by Acanthamoeba castellanii
CFU count of M. llatzerense after infection of A. castellanii pre-treated or not with rapamycin.(A). Colocalisation of live or heat-killed M. llatzerense within intracellular acidic compartments labelled with pHrodo (B). Statistical tests were performed using unpaired t-tests (P < 0.001***).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: CFU count of M. llatzerense after infection of A. castellanii pre-treated or not with rapamycin.(A). Colocalisation of live or heat-killed M. llatzerense within intracellular acidic compartments labelled with pHrodo (B). Statistical tests were performed using unpaired t-tests (P < 0.001***).
Mentions: In order to strengthen the results depicting significant changes of M. llatzerense gene expression during the early infection stage, we aimed to characterise its intracellular survival. Following internalisation, the resistance of M. llatzerense to A. castellanii degradation was assessed, by stimulating the autophagic machinery using rapamycin. Autophagy was described as a major pathway for blocking tuberculous mycobacteria proliferation in host cells, as its activation greatly affects mycobacteria survival4647. M. llatzerense survival was monitored for up to four hours after rapamycin treatment. Bacterial viability significantly decreased at 0, 1 and 4 hours after rapamycin treatment, as half of the bacilli survived compared to control condition (Fig. 6A). While significant, even in condition where bacterial degradation through phagocytosis and autophagy were strongly stimulated, we did not reach M. llatzerense total elimination, confirming its strong ability to resist A. castellanii degradation.

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