Comparison of multidrug resistant Salmonella between intensively - and extensively-reared antimicrobial - free (ABF) swine herds

Thumbnail Image
Thakur, Siddhartha
Tadesse, D.
Morrow, W. E. Morgan
Gebreyes, Wondwossen
Major Professor
Committee Member
Journal Title
Journal ISSN
Volume Title
Research Projects
Organizational Units
Journal Issue
Is Version Of
International Conference on the Epidemiology and Control of Biological, Chemical and Physical Hazards in Pigs and Pork
Iowa State University Conferences and Symposia

The SafePork conference series began in 1996 to bring together international researchers, industry, and government agencies to discuss current Salmonella research and identify research needs pertaining to both pig and pork production. In subsequent years topics of research presented at these conferences expanded to include other chemical and biological hazards to pig and pork production.


This cross-sectional study was conducted to determine the prevalence and antimicrobial resistance of Salmonella species in swine reared in the intensive (indoor) and extensive (outdoor) ABF production systems at farm and slaughter in North Carolina, U.S.A. We sampled a total of 279 pigs at farm (Extensive 107; Intensive 172) and collected 274 carcass swabs (Extensive 124; Intensive 150) at slaughter. Salmonella species were tested for their susceptibility against 12 antimicrobial agents using the Kirby-Bauer disk diffusion method. Serogrouping was done using polyvalent and group specific antisera. A total of 400 salmonellae were isolated in this study with a significantly higher Salmonella prevalence from the Intensive (30%) than the extensive farms (0.9%) (P < 0.001 ). At slaughter, significantly higher Salmonella was isolated at the pre and post-evisceration stages from extensively (29 % pre-evisceration and 33.3 % post-evisceration) than the intensively (2 % pre-ev1sceration and 6 % post-evisceration) reared swine (P < 0.001 ). The isolates were clustered in six serogroups including B, C, E1, E4, G and R. Highest frequency of antimicrobial resistance was observed against tetracycline (78.5%) and streptomycin (31 .5%). A total of 13 antimicrobial resistance patterns were observed including the pentaresistant strains with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline resistance pattern observed only among isolates from the intensive farms (n=28) and all belonged to serogroup B. This study shows that multidrug resistant Salmonella are prevalent in ABF production systems despite the absence of antimicrobial selection pressure.

Mon Jan 01 00:00:00 UTC 2007