Interaction between Vibrio cholerae and Acanthamoeba castellanii

Abstract

The environmental reservoirs of Vibrio cholerae strains are far from completely disclosed. Both V. cholerae strains and Acanthamoeba species are found in the aquatic environments of cholera endemic areas. It has been shown that Acanthamoeba species have gram-negative bacteria of different origin as endosymbionts. Previously it has been found that V. cholerae O139 can survive and grow intracellularly in Acanthamoeba castellanii. The aim of the present study was to compare serotypes of V. cholerae, other than V. cholerae O139, for their abilities to grow intracellularly in A. castellanii. Each of the following strains, the seventh-pandemic V. cholerae O1 El Tor-Inaba strain N16961, the sixth-pandemic V. cholerae O1 classical-Ogawa strain 395 and V. cholerae O54, were co-cultivated with A. castellanii to examine whether an interaction could be established. It was found that V. cholerae O1 El Tor-Inaba grew and survived in the presence of amoebae for > 2 weeks. V. cholerae O54 also showed growth although only for 1 week. Moreover, intracellular growth could be demonstrated, V. cholerae O1 El Tor-Inaba could be found in the amoeba trophozoites and cysts, while V. cholerae O54 could only be found in trophozoites. V. cholerae O1 classical-Ogawa was not found to be viable for > 3 days under similar conditions and thus no intracellular growth was recorded. Interestingly, the number of co-cultivated A. castellanii with each of the three strains increased at least threefold. In conclusion, these results show that a symbiotic relationship exists between A. castellanii and V. cholerae O1 El Tor-Inaba and V. cholerae O54, but not with the strain V. cholerae O1 classical-Ogawa, as both co-cultured and solely cultured V. cholerae O1 classical-Ogawa did not grow more than 3 days, and no intracellular growth of this strain could be detected in A. castellanii cells.