salicylates and Salmonella-Infections--Animal

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.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Cecum; Cell Line; Chickens; Disease Models, Animal; DNA-Binding Proteins; Escherichia coli Proteins; Humans; Intestinal Mucosa; Liver; Macrophages, Alveolar; Mutagenesis, Insertional; Phagocytosis; Poultry Diseases; Salicylates; Salmonella Infections, Animal; Salmonella typhimurium; Specific Pathogen-Free Organisms; Spleen; Swine; Virulence

Two similar trials were conducted to evaluate the effects of dietary inclusion of fructooligosaccharide (FOS) on live performance and carcass characteristics of broilers and on incidence and level of salmonellae on prechill broiler carcasses. The FOS was fed at two levels (0 and .375%) in a complete factorial arrangement with two levels (0 and 55 mg/kg) of bacitracin methylene disalicylate (BMD) in nutritionally complete diets. Broilers were grown to 49 days of age, and samples were processed to determine dressing percentage, abdominal fat content, and most probable number salmonellae on prechill carcasses. The addition of FOS to nutritionally complete broiler diets at .375% had little consistent effect on growth rate, feed utilization, mortality, carcass dressing percentage, abdominal fat content, or incidence or severity of salmonellae contamination of processed broiler carcasses. There appeared to be an antagonism between FOS and BMD on both live performance and salmonellae contamination of processed broiler carcasses.

Topics: Animal Feed; Animals; Bacitracin; Chickens; Coccidiostats; Colony Count, Microbial; Dietary Carbohydrates; Evaluation Studies as Topic; Female; Male; Oligosaccharides; Poultry Diseases; Salicylates; Salmonella Infections, Animal; Salmonella typhimurium