Submitted to: Rushmore Conference on Mechanisms in Pathogenesis of Enteric Diseases
Publication Type: Proceedings
Publication Acceptance Date: 1/11/1999
Publication Date: N/A
Citation: Interpretive Summary: Salmonella are bacteria that can cause sickness or death in humans or animals. There is concern that antibiotic resistance in these organisms could limit effective treatments in humans and animals; therefore, the current levels of antibiotic resistance in organisms such as Salmonella need to be determined. We tested approximately 400 Salmonella organisms using 13 different antibiotics. A high percentage of these organisms were found to be resistant to the more commonly used antibiotics. By determining the extent of antibiotic resistance in these organisms, the connection between the use of antibiotics in food-producing animals and the development of antibiotic resistant Salmonella can be explored. This information is important not only for the food-safety specialist, but for the producer as well. This could lead to a change in many of the production practices, such as the routine addition of antibiotics to feed and water for improved feed efficiency, that are currently used in the swine industry.
Technical Abstract: We conducted an epidemiological survey of antibiotic resistance in Salmonella recovered from market-age swine at 5 different Texas farms. These farms, which were visited between October 1997 and June 1998, were completely integrated, farrow-to-finish operations. Samples were taken from the lymph nodes and cecal contents at the time of slaughter. The Salmonella samples that were recovered were sent to the National Veterinary Services Laboratory for serotyping. Antibiotic resistance was determined using the Dispens-O-Disc Susceptibility Test System using 13 different antimicrobial agents that have been utilized in either veterinary medicine, human medicine, or both. Preliminary analysis of the first 183 samples out of approximately 400 Salmonella samples recovered indicated that 183 (100%) of the Salmonella samples were resistant to penicillin G, and 122 (66.7%) were resistant to chlortetracycline. Six (3.3%) were resistant to 4 antibiotics (chlortetracycline, penicillin G, streptomycin, and sulfisoxazole), and 25 (13.7%) were resistant to 3 antibiotics (chlortetracycline, penicillin G, and either streptomycin, sulfisoxazole, or ampicillin). Variation was seen between serotypes, with 4 out of 5 S. agona samples (80.0%) and 2 out of 8 S. derby samples (25.0%) resistant to 4 antibiotics. Variation in antibiotic resistance also was seen between farms. There is an increasing concern about the prevalent usage of antibiotics in medicine and agriculture and the relationship this may have on emerging microbial resistance patterns; therefore, continued surveillance on antibiotic resistance in animal production is warranted.