Uptake and replication in Acanthamoeba castellanii of a virulent (pVAPA-positive) strain of Rhodococcus equi and its isogenic, plasmid-cured strain. Academic Article uri icon


  • Rhodococcus equi is a soil saprophytic bacterium and intracellular pathogen that causes pneumonia in foals. Strains of R. equi that are virulent in foals contain a plasmid that encodes a virulence-associated protein A (VapA) necessary for replication in macrophages. Because other intracellular pathogens survive and replicate inside amoebae, we postulated that the VapA-bearing plasmid (pVAPA) confers a survival advantage for R. equi against environmental predators like amoebae. To test this hypothesis, we compared phagocytosis by and survival in Acanthamoeba castellanii of isogenic strains of pVAPA-positive and pVAPA-negative R. equi. Phagocytosis of the pVAPA-negative strain by A. castellanii was significantly (P < 0.0001) greater than the pVAPA-positive strain. Intracellular replication of the pVAPA-positive strain in A. castellanii was significantly (P < 0.0001) greater than the pVAPA-negative strain during both 48 h and 9 days. These results indicate that the presence of the VapA plasmid reduces uptake and aids replication of R. equi in A. castellanii.

published proceedings

  • Vet Microbiol

altmetric score

  • 1.5

author list (cited authors)

  • Allegro, A. R., Barhoumi, R., Bordin, A. I., Bray, J. M., & Cohen, N. D.

citation count

  • 0

complete list of authors

  • Allegro, Angelica R||Barhoumi, Rola||Bordin, Angela I||Bray, Jocelyne M||Cohen, Noah D

publication date

  • January 2021