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

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

M. llatzerense resists A. castellanii predation.For the droplet test, bacterial suspension (10 μL) were spotted on Middlebrook 7H10, 10% OADC, with or without an A. castellanii lawn. Mll: Mycobacterium llatzerense isolates EDP_1 to EDP_5; Ms: Mycobacterium septicum; Ec: Escherichia coli.
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f1: M. llatzerense resists A. castellanii predation.For the droplet test, bacterial suspension (10 μL) were spotted on Middlebrook 7H10, 10% OADC, with or without an A. castellanii lawn. Mll: Mycobacterium llatzerense isolates EDP_1 to EDP_5; Ms: Mycobacterium septicum; Ec: Escherichia coli.

Mentions: In a previous study, we showed the frequent co-occurrence of Mycobacterium llatzerense (80% to 90% of identified NTM sequences) in association with FLA isolated from a drinking water network33. This finding encouraged a better characterisation of M. llatzerense interactions with Acanthamoeba castellanii. In this study, environmental isolates of M. llatzerense were collected from endpoint sites of the above-mentioned drinking water network, provided by treated groundwater. Their resistance to A. castellanii was determined through a droplet test, for comparing the ability of bacterial isolates to grow in presence or absence of A. castellanii seeded on the agar medium. This ability was assessed for five M. llatzerense environmental isolates, as well as a strain of Mycobacterium septicum, moderately resistant to A. castellanii predation, and isolated from the same drinking water network. E. coli was used as a control, as it is a commonly used food source for FLA (Fig. 1). The five environmental M. llatzerense isolates developed similarly with or without the presence of A. castellanii lawn on the nutritive medium (Fig. 1). In comparison, the ability of M. septicum to grow was strongly impaired in the presence of A. castellanii, while E. coli growth was completely inhibited (Fig. 1). Based on these observations, M. llatzerense displayed a resistance to A. castellanii predation. As no difference in A. castellanii resistance were observed between M. llatzerense environmental isolates, one representative isolate, M. llatzerense EDP_4, was selected for the subsequent experiments.


Mycobacterium llatzerense , a waterborne Mycobacterium , that resists phagocytosis by Acanthamoeba castellanii
M. llatzerense resists A. castellanii predation.For the droplet test, bacterial suspension (10 μL) were spotted on Middlebrook 7H10, 10% OADC, with or without an A. castellanii lawn. Mll: Mycobacterium llatzerense isolates EDP_1 to EDP_5; Ms: Mycobacterium septicum; Ec: Escherichia coli.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: M. llatzerense resists A. castellanii predation.For the droplet test, bacterial suspension (10 μL) were spotted on Middlebrook 7H10, 10% OADC, with or without an A. castellanii lawn. Mll: Mycobacterium llatzerense isolates EDP_1 to EDP_5; Ms: Mycobacterium septicum; Ec: Escherichia coli.
Mentions: In a previous study, we showed the frequent co-occurrence of Mycobacterium llatzerense (80% to 90% of identified NTM sequences) in association with FLA isolated from a drinking water network33. This finding encouraged a better characterisation of M. llatzerense interactions with Acanthamoeba castellanii. In this study, environmental isolates of M. llatzerense were collected from endpoint sites of the above-mentioned drinking water network, provided by treated groundwater. Their resistance to A. castellanii was determined through a droplet test, for comparing the ability of bacterial isolates to grow in presence or absence of A. castellanii seeded on the agar medium. This ability was assessed for five M. llatzerense environmental isolates, as well as a strain of Mycobacterium septicum, moderately resistant to A. castellanii predation, and isolated from the same drinking water network. E. coli was used as a control, as it is a commonly used food source for FLA (Fig. 1). The five environmental M. llatzerense isolates developed similarly with or without the presence of A. castellanii lawn on the nutritive medium (Fig. 1). In comparison, the ability of M. septicum to grow was strongly impaired in the presence of A. castellanii, while E. coli growth was completely inhibited (Fig. 1). Based on these observations, M. llatzerense displayed a resistance to A. castellanii predation. As no difference in A. castellanii resistance were observed between M. llatzerense environmental isolates, one representative isolate, M. llatzerense EDP_4, was selected for the subsequent experiments.

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