Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2001
Publication Date: N/A
Interpretive Summary: The use of antibiotics in swine production is very common. This has raised concerns that the bacteria once killed by the antibiotics may be developing resistance to them. The purpose of the present study was to determine what antibiotics Salmonella may develop resistance to when the antibiotics carbadox and apramycin were fed to growing swine. Salmonella resistance to six different antibiotics was not increased when carbadox and apramycin were fed. This is important because antibiotics that may or may not be working must be identified.
Technical Abstract: The antibiotics apramycin and carbadox were fed to growing swine and the prevalence of colonization with Salmonella that are resistant to apramycin and related aminoglycoside antibiotics was examined. Three hundred and twelve Salmonella-positive pigs raised in an integrated swine operation and slaughtered at a central plant were used. All pigs received carbadox during the grower phase and some were treated with apramycin during the first 21 days of age. One hundred of the 312 pigs were randomly selected for examination of apramycin- and carbadox-resistant Salmonella in ileocolic lymph nodes and cecal contents at slaughter age. All 312 pigs were used to evaluate the association between apramycin exposure and colonization with Salmonella organisms resistant to amikacin, gentamicin, kanamycin, and streptomycin. Antimicrobial resistance was determined using disk diffusion and breakpoint concentrations. Apramycin treatment did not appear (P > .05) to increase the incidence of apramycin- (23.5 vs 13.6%) or streptomycin- (81.8 vs 76.3%) resistant Salmonella colonizations when compared to control animals. Feeding apramycin and carbadox resulted in the presence of carbadox-resistant Salmonella in only 2% of the pigs. The prevalence of amikacin, gentamicin, and kanamycin-resistant Salmonella in pigs fed apramycin were 0, 0, and 0.6%, respectively. In pigs exposed to apramycin, Salmonella colonization was most often found in serogroup C Salmonella isolates while pigs not exposed to apramycin were most often colonized by serogroup B isolates. In this study, sub-therapeutic use of carbadox and apramycin did not significantly increase the prevalence of antimicrobial-resistant Salmonella in market age swine.