SALMONELLA-TYPHIMURIUM ACRB-LIKE GENE - IDENTIFICATION AND ROLE IN RESISTANCE TO BILIARY SALTS AND DETERGENTS AND IN MURINE INFECTION

Salmonella serotype typhimurium transpositional mutants altered in res istance to biliary salts and detergents were isolated previously. We h ave characterized further the LX1054 mutant strain, the most sensitive of them. The chromosomal DNA segment flanking transposon insertion wa s cloned and sequenced. The highest level of identity was found for th e acrB (formerly acrE) gene of Escherichia coli, a gene encoding a dru g efflux pump of the Acr family. LX1054 exhibited a reduced capacity t o colonize the intestinal tract. After passages in mice, the mutant st rain lost the sensitive phenotype. In vitro, a resumption of growth ap peared after 17 h of culture in medium with cholate or other tested bi ological or chemical detergents. Then, the acquired resistant phenotyp e seemed stable. The data suggested a role of S. typhimurium acrB-like gene in resistance to biliary salts and detergents and in mice intest inal colonization. However, the local and transient sensitivity observ ed in vivo, and the in vitro adaptations suggest that several detergen t-resistance mechanisms operate in S. typhimurium.