Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 2/27/2000
Publication Date: 5/23/2000
Citation: Allen, C.A., Cray, P.J., Vasquez-Torres, A., Suyemoto, M., Altier, C., Fang, F.C., Libby, S.J. 2000. An in vitro and in vivo assessment of salmonella typhimurium dt104 virulence. American Society for Microbiology Annual Meeting. Session 140. D-179. P. 267. Interpretive Summary: N/A
Technical Abstract: Salmonella typhimurium definitive type 104 (DT104) has emerged as a serious zoonotic pathogen. DT104, a multi-drug resistant strain of S. typhimurium, is readily transmissible among a wide range of species, including humans, wildlife,pets, and livestock. S. typhimurium DT104, first isolated in the United Kingdom in the late 1980's, is now routinely found in Europe and North America. S. typhimurium DT104 typically possesses the penta-resistant phenotype ACSSuT, indicating resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. Because of the reported severity of disease caused by this organism, there has been increased speculation that S. typhimurium DT104 has enhanced virulence, or hypervirulence, in domestic animals and humans. In this study, we chose to examine the virulence of S. typhimirium DT104 isolates in the murine model system of systemic salmonellosis. In vitro, S. typhimurium DT104 virulence was measured using mouse macrophage survival assays, and tested for its ability to invade epithelial cells. The assessment of the ability of S. typhimurium DT104 to invade epithelial cells, survive in peritoneal macrophages, or cause lethal infection of genetically-resistant or -susceptible mice did not reveal evidence of enhanced nor reduced virulence when compared with ATCC S. typhimurium strain 14028s. Nor was there any evidence that the multi-drug resistant status of S. typhimurium DT104 had an attenuating effect on its virulence, consistent with recent observations suggesting that multi-drug resistant Salmonella strains maintain their competitive fitness. The increased prevalence of S. typhimurium DT104 is likely a result of competitive advantage conferred by the strain's resistance to multiple antimicrobial agents per se. Prophylactic use of antibiotics in food animal production may provide potent selection pressure for the emergence and persistence of multi-drug resistant strains like S. typhimurium DT104.