Salmonella in Broiler Flocks in the Republic of Ireland

In order to obtain an estimation of the prevalence of Salmonella spp. in flocks of broilers in the Republic of Ireland, a study was conducted in 2006 in a total of 362 broiler flocks associated with four integrated companies. Salmonella spp. was isolated from 27.3% of flocks, and eight Salmonella serovars were identified, none of which were Salmonella Enteritidis or Salmonella Typhimurium. The most prevalent serovar was Salmonella Mbandaka, followed by Salmonella Kentucky, which respectively accounted for 61.6% and 27.0% of positive samples. Notable differences were observed among the flocks associated with different integrated companies, both in the Salmonella spp. prevalence and in the serovar distribution. Results from routine official Salmonella testing in broiler production in 2006 showed similar serovar distribution within each integrated company from the associated hatchery and factory samples. In our study, differences in the prevalence of Salmonella at farm level did not correlate with differences in the percentages of positive chicken carcasses officially tested, which were low, for all the four companies investigated. Given the high prevalence of Salmonella Mbandaka, all human isolates obtained in the Republic of Ireland from 2003 to 2006 were compared to a subset of poultry isolates by pulsed-field gel electrophoresis, but an epidemiological link between the animal and the human strains could not be established. Finally the antimicrobial resistance analysis indicated a low proportion of resistant strains among the broiler flock isolates.