title: Effect of farm type on within-herd Salmonella prevalence, serovar distribution, and antimicrobial resistance.
abstract: Salmonella represents a major challenge to the pig industry, as pork presents a risk for human salmonellosis. In this study, we have examined the effect of farm type on the prevalence of fattening pigs shedding Salmonella on 12 farms at risk for harboring Salmonella.  On six open (grow-to-finish) and six closed (farrow-to-finish) farms, the prevalence of pigs shedding Salmonella was determined on two occasions approximately 2 months apart. The serovar, phage type, and antimicrobial resistance of the obtained Salmonella isolates were determined.  On all farms, pigs shedding Salmonella were detected on at least one of the two sampling days. The mean within-herd prevalence was 7.8%. Closed farms were two times less likely to have pigs shedding Salmonella than open farms. On open farms, the odds of finding Salmonella  shedding in pigs were 1.9 times higher when sampling was performed at slaughter age than when samples were taken halfway through the fattening period. Salmonella enterica serovar Typhimurium was the most predominant serotype, with a prevalence of 62 to 63% on both farm types. Of all  the Salmonella Typhimurium isolates, 65% had the tetraresistant profile ASSuT (ampicillin, streptomycin, sulfonamide, and tetracycline) with or without additional resistance to trimethoprim-sulfonamide. Phage type DT120 seemed to be especially associated with this antimicrobial-resistant  profile. The prevalence of Salmonella Typhimurium isolates showing resistance to ampicillin, streptomycin, tetracycline, sulfonamide, trimethoprim-sulfonamide, and lincomycin hydrochloride and spectinomycin sulfate tetrahydrate was significantly higher on open farms than on closed farms.
authors.affiliation: Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium. Geertrui.rasschaert@ilvo.vlaanderen.be
authors.forename: G
authors.initials: G
authors.lastname: Rasschaert
authors.forename: J
authors.initials: J
authors.lastname: Michiels
authors.forename: D
authors.initials: D
authors.lastname: Arijs
authors.forename: C
authors.initials: C
authors.lastname: Wildemauwe
authors.forename: S
authors.initials: S
authors.lastname: De Smet
authors.forename: M
authors.initials: M
authors.lastname: Heyndrickx
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D057138:Bacterial Shedding; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D006799:Housing, Animal; D006801:Humans; D015995:Prevalence; D012475:Salmonella / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification*; D012478:Salmonella Food Poisoning / Q000188:drug therapy / Q000453:epidemiology* / Q000209:etiology / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents