Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/28/2004
Publication Date: 6/28/2004
Citation: Carlson, S.A., Franklin, S.L., Rasmussen, M.A., Robens, J.F. 2004. Antibiotic resistance is linked to Salmonella survival in rumen protozoa [abstract]. Conference on Antimicrobial Resistance. p. 40.
Technical Abstract: Previous studies indicate that intracellular pathogens can be more virulent after survival within protozoa. Protozoa can also facilitate gene transfer when bacteria survive within digestive vacuoles. In this study, we sought to determine the relationship between protozoal predation in the rumen, Salmonella virulence and resistance to antibiotics. In order to investigate if such relationships exist, we determined the resistance status and virulence of Salmonella strains when recovered from lysed preparations of mixed rumen protozoa. Virulence was determined using a tissue culture invasion assay (HEp-2 human carcinoma cells) and by monitoring disease progression after oral inoculation of Salmonella into calves. Of the strains of bacteria investigated (n = 38), only those Salmonella strains possessing the DT104 gene cluster encoding antibiotic resistance were found to be hyperinvasive (5-10X greater than controls) after recovery from protozoa. When inoculated into calves, S. typhimurium DT104 recovered from rumen protozoa caused a more rapid disease progression, including increased pyrexia and greater recovery of bacteria from lymph nodes and spleen. We conclude that both predation survival and virulence are related to antibiotic resistance. The molecular mechanisms by which antibiotic resistance contributes to predation survival merit further investigation. These observations have implications for gene transfer and pathogen reservoir status. If rumen protozoa are a significant reservoir of resistance and virulence, periodic defaunation of the rumen may be warranted.