Shifts in the swine nasal microbiota of swine in response to different dosing regimens of oxytetracycline administration

Authors: MOU, KATHY - Oak Ridge Institute For Science And Education (ORISE); Allen, Heather; Alt, David; Trachsel, Julian; HAU, SAMANTHA - Oak Ridge Institute For Science And Education (ORISE); COETZEE, JOHANN - Kansas State University; HOLMAN, DEVIN - Lacombe Research Centre; Kellner, Steven; Loving, Crystal; Brockmeier, Susan

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2019
Publication Date: 10/2/2019
Citation: Mou, K.T., Allen, H.K., Alt, D.P., Trachsel, J.M., Hau, S.J., Coetzee, J.F., Holman, D.B., Kellner, S.G., Loving, C.L., Brockmeier, S. 2019. Shifts in the swine nasal microbiota of swine in response to different dosing regimens of oxytetracycline administration. Veterinary Microbiology. 237(1084020). https://doi.org/10.1016/j.vetmic.2019.108386.
DOI: https://doi.org/10.1016/j.vetmic.2019.108386

Interpretive Summary: Antibiotic stewardship is of the utmost importance to improve animal health outcomes and prevent selection of antimicrobial resistance. Several studies have shown how antibiotic treatment can alter the gut microbial community (microbiota) of pigs. There is increasing evidence of the important role the respiratory microbiota plays in shaping immune and respiratory health. However, there is little knowledge on the effects of antibiotics on the swine respiratory microbiota. Oxytetracycline is a broad-spectrum antibiotic that is labeled for treatment of bacterial respiratory disease in swine. This study characterized the impact of oxytetracycline administration, given either by injection or in feed, on the diversity of the nasal and tonsil microbiotas of post-weaned pigs. Results from this study revealed the nasal microbiota diversity decreased in response to both routes of oxytetracycline administration, but the tonsil microbiota was stable regardless of the route of administration. In addition, giving the antibiotic in the feed had a greater and longer lasting impact on the nasal microbiota than the injectable route, with changes in abundances of respiratory bacteria including increased abundances of some pathogenic bacteria and decreased abundances of known respiratory commensals. These results highlight the need to further assess how these changes can ultimately affect the animal’s respiratory health and risk to disease.

Technical Abstract: The impacts of antibiotic treatment and route of administration on the swine respiratory microbiota are poorly defined. To begin to address this, this study characterized the impact of oxytetracycline administration, given either parenterally or in feed, on the diversity of the nasal and tonsil microbiotas of post-weaned pigs over a two-week period. One group received a single intramuscular injection of oxytetracycline (IM), the second was treated with feed medicated with oxytetracycline (IF), and the final group received no antibiotic treatment (NON). Nasal samples were collected on days 0 (before start of treatment), 4, 7, 11, and 14. Tonsil tissue samples were collected from a subset of pigs selected for necropsy on days 4, 7, and 14. The results showed that the tonsil microbiota was stable regardless of antibiotic treatment. In contrast, the nasal bacterial diversity decreased for both oxytetracycline groups compared to NON. The IF group also exhibited decreased diversity on more days than the IM group. The nasal bacterial community structures of the antibiotic treatment groups were significantly different from the NON group that persisted from day 4 until day 7 for the IM group, and up until day 11 for the IF group. This included relative increased abundances of Actinobacillus and Streptococcus, and relative decreased abundances of multiple commensal genera. The microbiota of the IF group was also more disturbed than the microbiota of the IM group, relative to NON. This study revealed that short-term exposure to broad-spectrum antibiotics like oxytetracycline can disturb the upper respiratory microbiota, and the route of antibiotic administration has differential effects on the microbiota.