Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Protozoan expelled food vacuoles are an unrecognized vector for the transmission of cholera (#50)

Diane McDougald 1 2 , Gustavo Espinoza Vergara 1 3 , Parisa Noorian 1 , Shuyang Sun 1
  1. ithree Institute, University Of Technology Sydney, SYDNEY, NSW, Australia
  2. Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
  3. School of Biotechnology and Bimolecular Science, University of New South Wales, Sydney, NSW, Australia

Bacterivorous protists (protozoa) frequently release undigested bacteria in egested food vacuoles (EFV), which have, until now, been an unrecognized vector for the transmission of cholera.  Here we used confocal microscopy, exposure to stresses (pH and antibiotics) and the infant mouse model of colonisation to investigate stress resistance and infection potential of cells contained in the EFVs.

Our results show that Tetrahymena pyriformisreleases large numbers of EFVs when feeding on Vibrio cholerae.  EFVs were demonstrated to be extremely stable in artificial seawater with no significant loss of viability after long term storage at room temperature. Cells within the EFVs were not affected by incubation at low pH (3.5) or in the presence of antibiotics. When incubated at 37°C, the cells escaped very rapidly. Escaped cells were shown to have a fitness advantage over planktonic cells both in vitro and in vivo. These findings suggest that EFVs could facilitate the survival of V. choleraein the environment under a variety of stressful conditions and that the EFVs would also protect V. cholerae as it transits through the stomach. In addition, the escaped cells have enhanced colonisation potential. The work also shows that cells within EFVs are primed to cause infection and may be a significant contributor to the dissemination of epidemic V. choleraestrains.