Salmonella serotypes from 1997-2003 NARMS swine diagnostic, on-farm, and slaughter samples

Abstract

The veterinary component of the National Antimicorbial Resistance Monitoring System (NARMS) identified 8527 Salmonella isolates from swine samples in the years 1997-2003. Fiftyone Salmonella serotypes were identified from 3147 diagnostic, 2138 on-farm, and 3246 slaughter samples. The most frequently identified serotypes were Derby, Typhimurium var. Copehnagen, Typhimurium, Heidelberg, Infantis, Anatum, Johannesburg, and Agona. The top three serotypes from each sample type were as follows: Diagnostic; Cholera-suis (28.6%), Typhimurium var. Copenhagen (18.0%), Derby (9.5%); On-farm; Derby (18.5%), Agona (16.7%), Typhimurium var. Copenhagen (7.7%); Slaughter; Derby (25.4%), Typhimurium var. Copenhagen (10.6%), Johannesburg (6.7%). Six serotypes (Derby, Typhimurium var Copenhagen, Typhimurium, Heidelberg, Anatum, Agona) were found among top serotypes from each sample type. S. Cholerasuis was found primarily in diagnostic samples, and S. Johannesburg and Schwarzengrund were found primarily in slaughter samples. Only two of the top five slaughter isolates, Typhimurium and Infantis, were also seen on the 2002 CDC top 10 list of human isolates. Introduction The National Antimicrobial Resistance Monitoring System (NARMS) was established in 1996 by the Food and Drug Administration (FDA), the United States Department of Agriculture (USDA), and the Centers for Disease Control and Prevention (CDC) to monitor changes in antimicrobial susceptibilities of zoonotic pathogens from humans and animal diagnostic specimens, from healthy farm animals, and from raw product collected from federally inspected slaughter and processing plants. Non-typhoid Salmonella were selected as the sentinel organism and have been continuously tested for since 1997. This paper focuses on the serotype distribution of Salmonella which have been identified from all veterinary swine samples collected by the NARMS program from 1997-2003. Materials and Methods On-farm samples collected by USDA, APHIS or in special projects by USDA, ARS scientits and shipped to USDA, ARS in Athens, GA for cultural analysis in 1997, 1999, and 2000. Slaughter samples were collected and cultured by, USDA, FSIS, and diagnostic samples were collected and cultured by state veterinary laboratories around the U.S or the USDA, APHIS, National Veterinary Services Laboratory (NVSL). Slaughter and diagnostic were collected in all years and isolates shipped to USDA, ARS in Athens, GA. All Salmonella isolates were serotyped at the NVSL in Ames, IA. Results A broad representation of the Salmonella population is the U.S. swine industry is seen in the 8527 Salmonella from diagnostic, on-farm, and slaughter swine samples from the years 1997-2003. Isolates from 3147 diagnostic, 2138 on-farm, and 3246 slaughter samples yielded a total of 51 different serotypes. The eight most frequently identified serotypes of Salmonella were Derby, Typhimurium var. Copehnagen, Typhimurium, Heidelberg, Infantis, Anatum, Johannesburg, and Agona. The top three Salmonella serotypes from each sample type were as follows: Diagnostic; Cholera-suis (28.6%), Typhimurium var. Copenhagen (18.0%), Derby (9.5%); On-farm; Derby (18.5%), Agona (16.7%), Typhimurium var. Copenhagen (7.7%); Slaughter; Derby (25.4%), Typhimurium var. Copenhagen (10.6%), Johannesburg (6.7%). Six serotypes (Derby, Typhimurium var Copenhagen, Typhimurium, Heidelberg, Anatum, Agona) were found in the top ten serotypes from each sample type. Salmonella Cholera-suis was the most frequent (28.6%) serotype from diagnostic samples, and interestingly was not seen in on-farm samples and in only 2.1% of slaughter samples. S. Derby was by far the most frequent Salmonella seen for all sample types. In 1997 and 2003 there were about equal numbers of S. Derby seen in slaughter and diagnostic samples, but in 1998-