Association of Resistance to Bile Salts and Virulence in Salmonella typhimurium Strains ∗

Abstract

Summary and Conclusions

A strain of Salmonella typhimurium, RIA, unable to grow-in the presence of high concentrations of bile salts was less virulent for mice than 3 mutants which were not inhibited under the same conditions. Two of these were isolated on inhibitory medium, the third independently from a mouse which died following infection with avirulent strain RIA. A sensitive reversion from one of the resistant mutants exhibited a virulence pattern similar to that of the sensitive parent strain. Resistant bacteria produced greater damage to internal organs and were able to persist for longer periods of time in host animals although the incidence of fatal infection was only somewhat higher than in mice infected with bile sensitive organisms. Limited studies comparing bile sensitive and resistant strains of Salmonella paratyphi B yielded similar but less striking results(7). These observations indicated that salmonellae able to withstand the effect of bile salts were also better able to establish chronic infection in mice leaving relatively large numbers of survivors as carriers of the organisms.