title: Salmonella prevalence and antimicrobial susceptibility from the National Animal Health Monitoring System Swine 2000 and 2006 studies.
abstract: Concern about Salmonella contamination of food is compounded by fear that antimicrobials traditionally used to combat the infection will become useless due to rising antibiotic resistance. Livestock, in particular swine, often are blamed for illnesses caused by Salmonella  and for increasing antibiotic resistance due to use of antibiotics in pigs. As part of the National Animal Health Monitoring System Swine 2000 and 2006 studies, swine fecal samples were cultured for Salmonella. These samples were collected from 123 operations in 17 states in 2000 and  from 135 operations in 17 states in 2006. At each operation, 50 and 60 fecal samples were collected from late finisher pig pens in 2000 and 2006, respectively. Salmonella isolates were characterized to determine serogroup and serotype and were tested for susceptibility to a panel of  17 and 15 antimicrobial drugs in 2000 and 2006, respectively. A total of 5,470 and 7,788 samples were cultured for Salmonella in 2000 and 2006, respectively. Overall, 6.2% of the samples and 34.2% of the farms were positive for Salmonella in 2000. In 2006, 7.2% of the samples  and 52.6% of the farms were positive. Salmonella Derby, Salmonella Typhimurium var. 5- (formerly Salmonella Typhimurium var. Copenhagen), and Salmonella Agona were the three serotypes most often recovered in both study years. The most common antimicrobial  resistance pattern for Salmonella Derby in the two study years was resistance to streptomycin, sulfisoxazole, and tetracycline. Most isolates were resistant to tetracycline, sulfisoxazole, and streptomycin in both study years. The proportion of Salmonella isolates that were susceptible  to all antimicrobials (pansusceptible) was 38.1% in 2000 and 20.4% in 2006. The proportion of Salmonella isolates that were resistant to three or more antimicrobials (multidrug resistant) was similar in 2000 and in 2006 (52.8 and 57.7%, respectively).
authors.affiliation: Animal and Plant Health Inspection Service, Veterinary Services, Centers for Epidemiology and Animal Health, U.S. Department of Agriculture, 2150 Centre Avenue, Building B, Fort Collins, Colorado 80526-8117, USA. charles.a.haley@aphis.usda.gov
authors.forename: C A
authors.initials: CA
authors.lastname: Haley
authors.forename: D A
authors.initials: DA
authors.lastname: Dargatz
authors.forename: E J
authors.initials: EJ
authors.lastname: Bush
authors.forename: M M
authors.initials: MM
authors.lastname: Erdman
authors.forename: P J
authors.initials: PJ
authors.lastname: Fedorka-Cray
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005506:Food Contamination / Q000032:analysis*; D006801:Humans; D015995:Prevalence; D012475:Salmonella / Q000187:drug effects / Q000302:isolation & purification; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000209:etiology; D012481:Salmonella Infections, Animal / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D018571:Sentinel Surveillance / Q000662:veterinary; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission