Strain-dependent interactions ofandin co-culture.

Abstract

andare ubiquitous colonizers of swine tonsils that can cause systemic disease and death, under undefined conditions. It is not known, however, whether these 2 species interact during initial infection. To investigate whether such interactions occur, the objective of this study was to assess phenotypic differences between mono-and co-cultures ofandwhen representative strains with different virulence potential were co-culturedIn cross-streak screening experiments, some(GP) serovar strains (GP3, GP4, GP5) exhibited altered morphology with some(SS) serovar strains, such as SS2, but not with SS1. Co-culture with GP5 reduced hemolytic activity of SS1, but not of SS2. Although both SS strains outgrew GP isolates in biofilm co-cultures, strain type affected the number of planktonic or sessile cells in co-culture biofilms. Numbers of sessile SS1 increased in co-cultures, but not of GP3. Both planktonic and sessile SS2 increased in co-culture, whereas GP5 decreased. Sessile SS1 increased, but planktonic GP5 decreased in co-culture and planktonic SS2 increased, but sessile GP3 decreased when grown together. The SS2 strain had a competitive advantage over GP3 during mid-exponential co-culture in broth.is predicted to use more unique carbon sources, suggesting thatoutcompetesin growth and nutrient consumption. This work provides direction for future studies of phenotypic and genotypic interactions between these and other swine tonsil co-colonizers.