Submitted to: International Symposium on Epidemiology and Control of Salmonella in Pork
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/1999
Publication Date: N/A
Citation: Bahnson, P.B., Cray, P.J. 1999. Association of antimicrobial resistance patterns and reported usage of antimicrobials in commercial growing pigs production. International Symposium on Epidemiology and Control of Salmonella in Pork. 240-241. Interpretive Summary:
Technical Abstract: The relationship between microbial use and the development of resistance to antimicrobials has been demonstrated through both external models and has been observed clinically. However, the strength of this relationship in practical production systems has not been clearly quantified. We designed this study to examine the strength of the relationship between use of antimicrobials and the occurrence of antimicrobial resistence among Salmonella spp. collected from the same groups of growing pigs. Materials and Methods: As a part of a large study on risk factors associated with Salmonella shedding (1) and antimicrobial resistance (3) we collected fecal samples on 50 farms from slaughter age pigs over a two year period. All samples were individually cultured for Salmonella spp. using conventional techniques. Data were summarized to describe antimicrobial use and the prevalence of resistance. The association between reported antimicrobial use and detected antimicrobial resistance was tested by ANOVA, weighted for the number of Salmonella isolates per herd. Results: A total of 2174 samples were collected, from which 352 Salmonellae were isolated. One or more Samonella were detected among 36 of the 50 herds (62%). Antimicrobial resistance varied widely, and are reported in full for the larger dataset (2). Among the three antimicrobial use/resistance pairs tested, a statistically significant relationship (p<0.05) was found only for use of tetracyclines. Herds reporting therapeutic use of tetracyclines in the final growing phase had higher proportion of resistant Salmonella isolates (68.3%) than did herds that did not report use of tetracyclines (48.3%) (p=0.049). Although a casual link cannot be proven by this analysis, one likely explantation is that therapeutic use of tetracyclines selected for a increased proportion of tetracycline resistant organisms.