title: Mycobacterium avium bacilli grow saprozoically in coculture with Acanthamoeba polyphaga and survive within cyst walls.
abstract: Protozoans are gaining recognition as environmental hosts for a variety of waterborne pathogens. We compared the growth of Mycobacterium avium, a human pathogen associated with domestic water supplies, in coculture with the free-living amoeba Acanthamoeba polyphaga with the growth of M. avium when it was separated from amoebae by a 0.1-micron-pore-size polycarbonate membrane (in a parachamber). Although viable mycobacteria were observed within amoebal vacuoles, there was no significant difference between bacterial growth in coculture and bacterial growth in the parachamber. This suggests that M. avium is able to grow saprozoically on products secreted by the amoebae. In contrast, Legionella pneumophila, a well-studied intracellular parasite of amoebae, multiplied only in coculture. A comparison of amoebae infected with L. pneumophila and amoebae infected with M. avium by electron microscopy demonstrated that there were striking differences in the locations of the bacteria within amoebal cysts. While L. pneumophila resided within the cysts, M. avium was found within the outer walls of the double-walled cysts of A. polyphaga. These locations may provide a reservoir for the bacteria when environmental conditions become unfavorable.
authors.affiliation: Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. zma7@cdc.gov
authors.forename: M
authors.initials: M
authors.lastname: Steinert
authors.forename: K
authors.initials: K
authors.lastname: Birkness
authors.forename: E
authors.initials: E
authors.lastname: White
authors.forename: B
authors.initials: B
authors.lastname: Fields
authors.forename: F
authors.initials: F
authors.lastname: Quinn
mesh_terms: D000048:Acanthamoeba / Q000254:growth & development* / Q000382:microbiology* / Q000472:pathogenicity; D000818:Animals; D018920:Coculture Techniques; D004197:Disease Reservoirs; D017753:Ecosystem; D006801:Humans; D016952:Legionella pneumophila / Q000254:growth & development / Q000472:pathogenicity / Q000648:ultrastructure; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D015269:Mycobacterium avium Complex / Q000254:growth & development* / Q000472:pathogenicity / Q000648:ultrastructure
chemical_list: D008567:Membranes, Artificial