Vibrio cholerae O139 requires neither capsule nor LPS O side chain to grow inside Acanthamoeba castellanii

Vibrio cholerae, the causative agent of cholera, has the ability to grow and survive in the aquatic free-living amoeba Acanthamoeba castellanii. The aim of the present study was to examine the ability of the clinical isolate V. cholerae O139 MO10 to grow in A. castellanii and to determine the effect of the bacterial capsule and LPS O side chain on intracellular growth. Results from co-cultivation, viable counts, a gentamicin assay, electron microscopy and statistical analysis showed that the association of V. cholerae O139 MO10 with A. castellanii did not inhibit growth of the amoeba, and enhanced growth and survival of V. cholerae O139 MO10 occurred. The wild-type V. cholerae O139 MO10 and a capsule mutant or capsule/LPS double mutant grew inside A. castellanii. Neither the capsule nor the LPS O side chain of V. cholerae O139 was found to play an important role in the interaction with A. castellanii, disclosing the ability of V. cholerae to multiply and survive inside A. castellanii, as well as the role of A. castellanii as an environmental host for V. cholerae.