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Open Access Research article

Surviving within the amoebal exocyst: the Mycobacterium avium complex paradigm

Iskandar Ben Salah1 and Michel Drancourt12*

Author Affiliations

1 Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UMR CNRS-6236, IRD 189, IFR 48 Faculté de Médecine, Université de la Méditerranée, Marseille France

2 Assistance Publique des Hôpitaux de Marseille, Fédération de Microbiologie clinique Hôpital la Timone Marseille-France

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BMC Microbiology 2010, 10:99  doi:10.1186/1471-2180-10-99

Published: 1 April 2010

Abstract

Background

Most of environmental mycobacteria have been previously demonstrated to resist free-living amoeba with subsequent increased virulence and resistance to antibiotics and biocides. The Mycobacterium avium complex (MAC) comprises of environmental organisms that inhabit a wide variety of ecological niches and exhibit a significant degree of genetic variability. We herein studied the intra-ameobal location of all members of the MAC as model organisms for environmental mycobacteria.

Results

Type strains for M. avium, Mycobacterium intracellulare, Mycobacterium chimaera, Mycobacterium colombiense, Mycobacterium arosiense, Mycobacterium marseillense, Mycobacterium timonense and Mycobacterium bouchedurhonense were co-cultivated with the free-living amoeba Acanthamoeba polyphaga strain Linc-AP1. Microscopic analyses demonstrated the engulfment and replication of mycobacteria into vacuoles of A. polyphaga trophozoites. Mycobacteria were further entrapped within amoebal cysts, and survived encystment as demonstrated by subculturing. Electron microscopy observations show that, three days after entrapment into A. polyphaga cysts, all MAC members typically resided within the exocyst.

Conclusions

Combined with published data, these observations indicate that mycobacteria are unique among amoeba-resistant bacteria, in residing within the exocyst.