Survival of enterohemorrhagic Escherichia coli in the presence of Acanthamoeba castellanii and its dependence on Pho regulon

Authors

  • Samuel Mohammed Chekabab,

    1. Centre de Recherche en Infectiologie Porcine (CRIP), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada
    Search for more papers by this author
  • France Daigle,

    1. Centre de Recherche en Infectiologie Porcine (CRIP), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada
    2. Department of Microbiology and Immunology, Université de Montréal, Montréal, Québec, Canada
    Search for more papers by this author
  • Steve J. Charette,

    1. Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, Québec City, Québec, Canada
    2. Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec (Hôpital Laval), Québec City, Québec, Canada
    3. Départment de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, Québec City, Québec, Canada
    Search for more papers by this author
  • Charles M. Dozois,

    1. Centre de Recherche en Infectiologie Porcine (CRIP), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada
    2. INRS-Institut Armand-Frappier, Laval, Québec, Canada
    Search for more papers by this author
  • Josée Harel

    Corresponding author
    • Centre de Recherche en Infectiologie Porcine (CRIP), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada
    Search for more papers by this author

Correspondence

Josée Harel, Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Faculté de Médecine Vétérinaire, C.P. 5000, Saint-Hyacinthe, Québec,

Canada J2S 7C6.

Tel: +1 450  773-8521;

Fax: +1 450  778-8108;

E-mail josee.harel@umontreal.ca

Abstract

Enterohemorrhagic Escherichia coli (EHEC) are involved in outbreaks of food-borne illness and transmitted to humans through bovine products or water contaminated by cattle feces. Microbial interaction is one of the strategies used by pathogenic bacteria to survive in the environment. Among protozoa, the free-living amoebae are known to host and protect several water-borne pathogens. In this study, the interaction between EHEC and the predacious protozoa Acanthamoeba castellanii was investigated. Using monoculture and cocultures, growth of both organisms was estimated for 3 weeks by total and viable cell counts. The numbers of EHEC were significantly higher when cultured with amoebae than without, and less EHEC shifted into a viable but nonculturable state in the presence of amoebae. Using several mutants, we observed that the Pho regulon is required for EHEC growth when cocultured with amoebae. In contrast, the Shiga toxins (Stx) were not involved in this association phenotype. Cocultures monitored by electron microscopy revealed a loss of the regular rod shape of EHEC and the secretion of multilamellar vesicles by the amoebae, which did not contain bacteria. As the interaction between A. castellanii and EHEC appears beneficial for bacterial growth, this supports a potential role for protozoa in promoting the persistence of EHEC in the environment.

Ancillary