title: Role of the mar locus in virulence of Salmonella enterica serovar Typhimurium DT104 in chickens.
abstract: The virulence of a Salmonella enterica serovar Typhimurium DT014 strain in which marA was insertionally inactivated was compared to its isogenic parent in vitro and in vivo. In vitro, the numbers of the marA mutant phagocytosed by porcine lung macrophages were significantly increased, while survival at 24 h inside macrophages and adherence to human gut cells were significantly reduced in comparison with the parent strain. In vivo, the marA inactivated strain, in competition with its parent strain, persisted for a shorter period in chickens, was present in the caeca at significantly lower levels and invaded the deeper organs to a significantly lesser extent. Therapeutic antibiotic treatment of one group of chickens with oxytetracycline favoured the persistence of both the parent strain and, to a lesser extent, the marA inactivated strain; but interestingly, increased tetracycline resistance of Salmonella isolates after treatment of birds with antibiotic was seen only for the parent strain. Further work is needed to elucidate how mar is involved in virulence and if its inactivation can minimise the ability of bacteria to become antibiotic-resistant in vivo.
authors.affiliation: Department of Bacteriological Diseases, Veterinary Laboratories Agency (Weybridge), New Haw, Addlestone, Surrey KT15 3NB.
authors.forename: L P
authors.initials: LP
authors.lastname: Randall
authors.affiliation: Department of Bacteriological Diseases, Veterinary Laboratories Agency (Weybridge), New Haw, Addlestone, Surrey KT15 3NB.
authors.forename: M J
authors.initials: MJ
authors.lastname: Woodward
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000235:genetics*; D002432:Cecum / Q000382:microbiology; D002460:Cell Line; D002645:Chickens / Q000382:microbiology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004195:Disease Models, Animal; D029968:Escherichia coli Proteins; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000382:microbiology; D008099:Liver / Q000382:microbiology; D016676:Macrophages, Alveolar / Q000276:immunology; D016254:Mutagenesis, Insertional; D010587:Phagocytosis; D011201:Poultry Diseases / Q000188:drug therapy / Q000382:microbiology*; D012459:Salicylates / Q000378:metabolism; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000382:microbiology; D013552:Swine; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; D012459:Salicylates