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

Abstract

Mycobacterium avium subsp. paratuberculosis is responsible for paratuberculosis in animals. This disease, leading to an inflammation of the gastrointestinal tract, has a high impact on animal health and an important economic burden. The environmental life cycle of M. avium subsp. paratuberculosis is poorly understood and several studies suggest that free-living amoebae (FLA) might be a potential environmental host. FLA are protozoa found in water and soil that are described as reservoirs of pathogenic and non-pathogenic bacteria in the environment. Indeed, bacteria able to survive within these amoebae would survive phagocytosis from immune cells. In this study, we assessed the in vitro interactions between several strains of M. avium subsp. paratuberculosis and Acanthamoeba castellanii. The results indicate that the bacteria were able to grow within the amoeba and that they can survive for several days within their host. To explore the presence of M. avium subsp. paratuberculosis in environmental amoebae, we sampled water from farms positive for paratuberculosis. A M. avium subsp. paratuberculosis strain was detected within an environmental amoeba identified as related to the poorly described Rosculus genus. The bacterial strain was genotyped, showing that it was similar to previous infectious strains isolated from cattle. In conclusion, we described that various M. avium subsp. paratuberculosis strains were able to grow within amoebae and that these bacteria could be found on farm within amoebae isolated from the cattle environment. It validates that infected amoebae might be a reservoir and vector for the transmission of M. avium subsp. paratuberculosis.

Acanthamoeba castellanii as a Screening Tool for Mycobacterium avium Subspecies paratuberculosis Virulence Factors with Relevance in Macrophage Infection

“…MAH has been characterized to possess increased virulence when isolated from amoeba [ 10 ] and express similar phenotype after infection of mammalian macrophages [ 31 , 32 ]. Likewise, amoeba has been shown to host MAP and serve as a potential reservoir for the long-term bacterial survival in the soil of farm pastures [ 12 ] and expressing enhanced resistance to common disinfectant treatments including chlorine and antibiotics [ 33 , 34 ].…”

“…The fact is that MAP resides in the environment after being shed in the feces from infected animals and can interact with a variety of species of protozoa in the soil. While MAP has been frequently isolated from amoeba [ 12 ], free-living amoeba has been frequently isolated from habitats common to mycobacteria [ 13 , 14 ], supporting an “endosymbiotic” relationship between mycobacteria and free-living protozoan host [ 15 , 16 ]. In addition, while mycobacteria have evolved mechanisms to survive within amoeba, amoeba would possibly protect phagocytized mycobacteria from adverse environmental insults, including extreme temperature, drought, and diverse biocide attacks via cyst formation [ 17 ].…”

Mycobacterium Avium Paratuberculosis: A Disease Burden on the Dairy Industry

“…Once MAP has successfully colonized the ruminant gut, the tissues develop a characteristic granuloma, histological, and gross appearance, leading ultimately to a lack of nutrient absorption [ 31 ] and malnutrition in the animal. The characteristic signs of advanced stage disease in cattle is copious diarrhea and visual appearance of the ribs and other skeletal bones [ 32 ]. Disseminated or systemic infections were thought to occur when the disease was at this advanced stage.…”

“…Estimates show global economic losses exceeding 1.5 billion US dollars annually from endemic cases of Johne’s disease [ 32 ]. Economic losses in dairy industries across the globe relate to production impact and disease control costs.…”

“…At present, there is no effective vaccine available for MAP which can be utilized, and the disease remains untreatable. Additionally, the current vaccine for MAP, which has questionable efficacy, compromises the diagnosis of bovine tuberculosis in cattle [ 32 ]. Prevention of disease at farm level and reducing vertical transmission are key areas where control needs to be implemented.…”