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United States Department of Agriculture

Agricultural Research Service

Title: Epidemiological Survey of Antimicrobial-Resistant Salmonella in Market-Age Swine

Authors
item Harvey, Roger
item Farrington, L - TEXAS A&M UNIVERSITY
item Buckley, Sandra
item Stanker, Larry
item Inskip, P - TEXAS A&M UNIVERSITY

Submitted to: International Symposium on Epidemiology and Control of Salmonella in Pork
Publication Type: Proceedings
Publication Acceptance Date: August 20, 1999
Publication Date: N/A

Interpretive Summary: There is increasing concern about the emergence of antibiotic resistant bacteria and their threat to human health. It has been questioned whether the use of antibiotics in animal production has promoted antibiotic resistance. We studied the antibiotic resistance patterns of Salmonella bacteria isolated from swine in a commercial operation. This is important from a public health standpoint because it will allow us to correlate resistance patterns with antibiotic usage in animals and to see if there is any carryover of resistance into human medicine.

Technical Abstract: We conducted a survey of antibiotic resistance in Salmonella isolated from market-age swine at five different farms. Samples were taken from the lymph nodes and cecal contents at the time of slaughter. Of the 559 Salmonella isolates recovered, 420 were sent to the National Veterinary Services Laboratory for serotyping. Resistance patterns were determined by disk diffusion using thirteen antibiotics, and 320 isolates were analyzed. Resistance was observed to ampicillin, chloramphenicol, chlortetracycline, nitrofurantoin, penicillin G, streptomycin and sulfisoxazole. Multi-drug resistance (resistance to two or more antibiotics) was observed in 183 isolates (57.2%) with 34 of these isolates (18.6%) resistant to three antibiotics and 26 (8.1%) resistant to four antibiotics. The most common three drugs resistance pattern consisted of chlortetracycline, penicillin G and streptomycin (37.3%). A significant difference was observed between serotypes and between somatic serogroups in their antibiotic resistance patterns. Variation also was observed between farms and between seasons in which sampling occurred. As a step in understanding the connection between antibiotic use in agriculture and medicine and emergence of antibiotic resistant bacteria, programs that monitor the levels of antibiotic resistance must be continued. In animal production, where sub-therapeutic administration of antibiotics is extremely common, continued surveillance is especially important.

Last Modified: 9/2/2014