Student Case Presentation
Antimicrobial resistance of Pasteurellacea in the upper respiratory tract of feedlot goats
| Date/Time: |
9/12/2024 13
|
| Presenter: |
Adam Steffensmeier |
| Veterinary School: |
IA |
Abstract:
Introduction:
Respiratory disease is the leading cause of poor performance and increased mortality for goats, and Mannheimia haemolytica and Pasteurella multocida are the most prevalent bacteria isolated. The increasing popularity of goats and frequent requirement for extralabel drug use due to a lack of labeled treatment options suggests the need for research on proper antimicrobial usage, including surveillance for antimicrobial resistance in respiratory pathogens of goats.
Materials and Methods:
Weaned intact and castrated males were sourced from multiple states and shipped to a central Iowa feedlot as part of a research trial. Deep nasopharyngeal samples were collected on arrival and again several weeks after group treatment for control of respiratory disease with tulathromycin. The nasopharyngeal swabs were streaked for isolation and M. hemolytica and P. multocida isolates were confirmed via MALDI-TOF. Antimicrobial susceptibility of isolates was tested via the BOPO7 Sensititre plate; the minimum inhibitory concentration (MIC) was recorded and bovine clinical breakpoints (CLSI) were utilized to assess for resistance.
Results:
From 18 of 52 goats sampled on arrival, MALDI-TOF confirmed the presence of 12 isolates of M. haemolytica and 9 isolates of P. multocida (3 goats provided 2 isolates of M. haemolytica). All isolates were pan-susceptible to all antimicrobials using bovine clinical breakpoints except a single M. haemolytica resistant to penicillin. From 9 goats resampled two weeks after treatment, 5 still harbored M. haemolytica, and 2 P. multocida. While the P. multocida remained pan-susceptible, all M. haemolytica isolates exhibited the same resistance pattern to macrolides (gamithromycin and tulathromycin, but not tildipirosin), tetracyclines, and beta-lactams (ampicillin, penicillin).
Conclusion:
Based on bovine clinical breakpoints, resistance to several antibiotics was noted following antibiotic exposure in this population of feedlot goats, suggestive of horizontal spread of a resistant clone. Further investigation of the impact of antimicrobial resistance in goat respiratory pathogens is warranted.
