Vibrio cholerae is the responsible agent of the acute diarrhoeal disease cholera. For many years V. cholerae has been studied as an extracellular and non-inflammatory bacterium in association with eukaryotic cells, as well as a persistent inhabitant of marine environments. Recently, several reports show that V. cholerae can survive and multiply inside of eukaryotic microorganisms such as amoebae and ciliates. By employing methods developed for the study of phagosomal trafficking of intracellular pathogens in macrophage, we identify the mechanisms mediated by V. cholerae O1 A1552 that allow its intracellular survival within protozoan hosts.
Co-incubation assays of V. cholerae with Acanthamoeba castellanii and Tetrahymena pyriformis are performed in artificial sea water. Molecular tools such as the transposon sequencing technology, antibody staining and confocal microscopy are used to identify mechanisms of intracellular trafficking of this bacterium in the protist.
Recent results indicate that i) actin microfilaments are involved in bacterial uptake, ii) genes related to intracellular growth (ankB) and intracellular disruption processes (rtxA) are not involved in the intracellular resistance of V. cholerae A1552 to digestion or in the release of egested food vesicles (EFVs) containing bacteria. Interestingly, this study shows that the EFVs contain live bacterial cells that are protected from environmental stresses. Moreover, exposing EFVs to the infant mouse model of infection reveals that EFVs aid in V. cholerae colonisation of the intestinal tract, and are therefore a previously unrecognised mechanism of transmission.