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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 persists and grows within A. castellanii.(A) Cell count of A. castellanii infected by M. llatzerense over-time. (B) CFU counts of M. llatzerense after A. castellanii infection at a MOI of 1 for 16 h. Each ratio was calculated with respect to the same condition without A. castellanii, where no significant growth was observed for M. llatzerense alone (data not shown). Statistical tests were performed using multiple unpaired t-tests (P < 0.05*P < 0.01**).
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f2: M. llatzerense persists and grows within A. castellanii.(A) Cell count of A. castellanii infected by M. llatzerense over-time. (B) CFU counts of M. llatzerense after A. castellanii infection at a MOI of 1 for 16 h. Each ratio was calculated with respect to the same condition without A. castellanii, where no significant growth was observed for M. llatzerense alone (data not shown). Statistical tests were performed using multiple unpaired t-tests (P < 0.05*P < 0.01**).

Mentions: To confirm M. llatzerense resistance ability, its fate within A. castellanii was investigated during co-culture lasting up to 96 hours. This time course was chosen as it represents the longer incubation time inducing less than 10% A. castellanii encystment in the non-nutritive PAS buffer, the medium used for infection experiments. After 4 h of infection, about 10% of A. castellanii were infected, and reached 40% after 16 h (Fig. 2A). This infection rate was maintained without significant differences up to 96 h post infection. During the time course of the experiment, M. llatzerense viability was assessed using CFU counting. Viable mycobacteria were recovered at all time points of the experiments, demonstrating their resistance to A. castellanii phagocytosis (Fig. 2B). A significant growth was even observed, starting at 72 h (P < 0.05; unpaired t-test) and reaching a 1.5 log10 growth at 96 h post-infection (P < 0.01; unpaired t-test) (Fig. 2B).


Mycobacterium llatzerense , a waterborne Mycobacterium , that resists phagocytosis by Acanthamoeba castellanii
M. llatzerense persists and grows within A. castellanii.(A) Cell count of A. castellanii infected by M. llatzerense over-time. (B) CFU counts of M. llatzerense after A. castellanii infection at a MOI of 1 for 16 h. Each ratio was calculated with respect to the same condition without A. castellanii, where no significant growth was observed for M. llatzerense alone (data not shown). Statistical tests were performed using multiple unpaired t-tests (P < 0.05*P < 0.01**).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: M. llatzerense persists and grows within A. castellanii.(A) Cell count of A. castellanii infected by M. llatzerense over-time. (B) CFU counts of M. llatzerense after A. castellanii infection at a MOI of 1 for 16 h. Each ratio was calculated with respect to the same condition without A. castellanii, where no significant growth was observed for M. llatzerense alone (data not shown). Statistical tests were performed using multiple unpaired t-tests (P < 0.05*P < 0.01**).
Mentions: To confirm M. llatzerense resistance ability, its fate within A. castellanii was investigated during co-culture lasting up to 96 hours. This time course was chosen as it represents the longer incubation time inducing less than 10% A. castellanii encystment in the non-nutritive PAS buffer, the medium used for infection experiments. After 4 h of infection, about 10% of A. castellanii were infected, and reached 40% after 16 h (Fig. 2A). This infection rate was maintained without significant differences up to 96 h post infection. During the time course of the experiment, M. llatzerense viability was assessed using CFU counting. Viable mycobacteria were recovered at all time points of the experiments, demonstrating their resistance to A. castellanii phagocytosis (Fig. 2B). A significant growth was even observed, starting at 72 h (P < 0.05; unpaired t-test) and reaching a 1.5 log10 growth at 96 h post-infection (P < 0.01; unpaired t-test) (Fig. 2B).

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