This cross-sectional study described antimicrobial resistance (AMR) in healthy pigs in 20 Alberta and Saskatchewan herds. All herds used antimicrobials; the daily probability of antimicrobial exposure was 0.8 for nursery pigs and 0.3 for grow-finish pigs. Salmonella spp. (n = 468) were isolated from nursery, grow-finish pigs and sows while <i>Escherichia coli</i> (n = 1439) and <i>Campylobacter</i> spp. (n = 405) were isolated from grow-finish pigs. <p>Fifty-nine percent of the Salmonella were pansusceptible. Isolates from sows were more likely to be pansusceptible than those from other production phases, while Salmonella from nursery pigs were more likely to be multiresistant. All Salmonella and E. coli were susceptible to ceftriaxone and ciprofloxacin, drugs critically important to human medicine, while one E. coli was resistant to ceftiofur. Resistance was most common to tetracycline and sulfamethoxazole (Salmonella, 35% and 27%; E. coli, 68% and 46%). Although often considered an indicator organism, <i>E. coli</i> AMR was a poor sentinel for Salmonella AMR at the herd-level. <p>Antimicrobial resistance genes, described in 151 <i>E. coli</i>, were associated in two sets: aadA1 / sul1 / tetA and blaTEM / strA strB / sul2 / tetB. Associations between genes consistently matched associations between phenotypes suggesting phenotype data may be useful for predicting co-selection. Demonstrating dose-response relationships between various antimicrobial exposures and resistance phenotypes in E. coli reiterated the importance of co-selection. Significant predictors included exposures in other production phases and to unrelated drugs. Four <i>E. coli </i> resistance-phenotypes were associated with macrolide exposure; the most commonly used antimicrobial class in study herds. Additionally, 70% of the Campylobacter were resistant to a macrolide and this resistance was associated with macrolide exposure in nursery pigs. Study herds did not use quinolones. Despite this, 15% of Campylobacter were resistant to a quinolone. Both Campylobacter and <i>E. coli</i> AMR clustered within herds, indicating on-farm interventions could mitigate AMR in pigs.<p>This study described AMR in enteric bacteria from healthy pigs. Identifying dose-response relationships between antimicrobial resistances and exposures to unrelated drugs, and exposures of pigs in different production phases, emphasize the importance of judicious antimicrobial use in pig production.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-09182007-095646 |
| Date | 21 September 2007 |
| Creators | Rosengren, Leigh |
| Contributors | Reid-Smith, Richard, McEwen, Scott, Harding, John, Dowling, Patricia M., Waldner, Cheryl |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-09182007-095646/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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