sodium-dodecyl-sulfate and Salmonella-Infections--Animal

Salmonella enterica subsp. enterica serovar Enteritidis is a leading causative agent of gastroenteritis in humans. This pathogen also colonizes the intestinal tracts of poultry and can spread systemically in chickens. Transfer to humans usually occurs through undercooked or improperly handled poultry meat or eggs. The bacterial twin-arginine transport (Tat) pathway is responsible for the translocation of folded proteins across the cytoplasmic membrane. In order to study the role of the Tat system in the infection and colonization of chickens by Salmonella Enteritidis, we constructed chromosomal deletion mutants of the tatB and tatC genes, which are essential components of the Tat translocon. We observed that the tat mutations affected bacterial cell morphology, motility, and sensitivity to albomycin, sodium dodecyl sulfate (SDS), and EDTA. In addition, the mutant strains showed reduced invasion of polarized Caco-2 cells. The wild-type phenotype was restored in all our Salmonella Enteritidis tat mutants by introducing episomal copies of the tatABC genes. When tested in chickens by use of a Salmonella Enteritidis Delta tatB strain, the Tat system inactivation did not substantially affect cecal colonization, but it delayed systemic infection. Taken together, our data demonstrated that the Tat system plays a role in Salmonella Enteritidis pathogenesis.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Caco-2 Cells; Chickens; Edetic Acid; Epithelial Cells; Ferrichrome; Gene Deletion; Genetic Complementation Test; Humans; Locomotion; Poultry Diseases; Salmonella enteritidis; Salmonella Infections, Animal; Sodium Dodecyl Sulfate; Virulence; Virulence Factors

SmpA is a small outer-membrane lipoprotein that is a component of the essential YaeT outer-membrane protein assembly complex. In Salmonella enterica serovar Typhimurium (S. Typhimurium), expression of the smpA gene was shown to be directed by two promoters, smpAp1 and smpAp2. The more distal promoter, smpAp1, is dependent upon the extracytoplasmic stress response sigma factor sigma(E). An smpA null mutant was constructed in S. Typhimurium SL1344 and was shown to be more sensitive than its wild-type parent to growth at high temperature and in the presence of sodium cholate, SDS plus EDTA, and the hydrophobic antibiotic rifampicin. The lack of SmpA in S. Typhimurium elicits a sigma(E)-dependent stress response. These findings are indicative of altered outer-membrane integrity in the smpA mutant, probably due to a defect in outer-membrane protein biogenesis. SmpA was not important for entry or survival within murine macrophages; however, the S. Typhimurium smpA mutant was attenuated in mice by both the oral and parenteral routes of infection, and SmpA appeared to be most important for the growth of S. Typhimurium at systemic sites.

Topics: Animals; Anti-Bacterial Agents; Bacterial Outer Membrane Proteins; Bacterial Proteins; Base Sequence; Edetic Acid; Gene Deletion; Gene Order; Hot Temperature; Lethal Dose 50; Liver; Lymph Nodes; Macrophages; Mice; Mice, Inbred BALB C; Microbial Viability; Molecular Sequence Data; Peyer's Patches; Promoter Regions, Genetic; Rifampin; Salmonella Infections, Animal; Salmonella typhimurium; Sigma Factor; Sodium Dodecyl Sulfate; Spleen; Transcription Factors; Transcription, Genetic; Virulence; Virulence Factors

Salmonella serotype typhimurium transpositional mutants altered in resistance to biliary salts and detergents were isolated previously. We have characterized further the LX1054 mutant strain, the most sensitive of them. The chromosomal DNA segment flanking transposon insertion was cloned and sequenced. The highest level of identity was found for the acrB (formerly acrE) gene of Escherichia coli, a gene encoding a drug efflux pump of the Acr family. LX1054 exhibited a reduced capacity to colonize the intestinal tract. After passages in mice, the mutant strain lost the sensitive phenotype. In vitro, a resumption of growth appeared after 17 h of culture in medium with cholate or other tested biological or chemical detergents. Then, the acquired resistant phenotype seemed stable. The data suggested a role of S. typhimurium acrB-like gene in resistance to biliary salts and detergents and in mice intestinal colonization. However, the local and transient sensitivity observed in vivo, and the in vitro adaptations suggest that several detergent-resistance mechanisms operate in S. typhimurium.

Topics: Amino Acid Sequence; Animals; Bacterial Proteins; Base Sequence; Carrier Proteins; Cholic Acids; Cloning, Molecular; Drug Resistance, Microbial; Escherichia coli Proteins; Female; Genes, Bacterial; Intestines; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microbial Sensitivity Tests; Molecular Sequence Data; Multidrug Resistance-Associated Proteins; Mutation; Salmonella Infections, Animal; Salmonella typhimurium; Sequence Analysis, DNA; Sodium Dodecyl Sulfate