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Research Summary - 1

Prevalence and antimicrobial susceptibility of bovine respiratory disease pathogen isolates submitted to the Wisconsin Veterinary Diagnostic Laboratory: 2008-2017

Date/Time: 9/12/2019    14:00
Author: Chelsea  Holschbach
Clinic: UW-Madison SVM
City, State, ZIP: Madison, WI  53706

Prevalence and antimicrobial susceptibility of bovine respiratory disease pathogen isolates submitted to the Wisconsin Veterinary Diagnostic Laboratory: 2008-2017

C.L. Holschbach, DVM 1 ; K.P. Poulsen, DVM, PhD, DACVIM 2 ; N.A. Aulik, PhD 2 ; T.L. Ollivett, DVM, PhD, DACVIM 1 ;
1Department of Medical Sciences, University of Wisconsin School of Veterinary Medicine, Madison, WI, 53706
2Wisconsin Veterinary Diagnostic Laboratory, Madison, WI 53706


Respiratory disease negatively impacts growth, reproductive performance, milk production, and longevity of adult cattle. Most calves diagnosed with clinical respiratory disease on dairy farms are treated with antibiotics. Treatment failure is not uncommon and although management factors likely contribute to these treatment failures, the role of antimicrobial resistance cannot be ruled out. Therefore, the objective of this study was to describe pathogen prevalence and antimicrobial resistance patterns for pathogens associated with respiratory disease isolated from samples submitted to the Wisconsin Veterinary Diagnostic Laboratory between 2008-2017.

Materials and Methods:

Data were retrospectively collected on all bovine respiratory isolates of Pasteurella multocida, Mannheimia hemolytica, Bibersteinia trehalosi, and Histophilus somni identified at the Wisconsin Veterinary Diagnostic Laboratory 2008 - 2017, using the Laboratory Information Management System. Antimicrobial susceptibility testing data were queried from antimicrobial resistance databases at the WVDL Madison and Barron locations.

During that ten-year period, MIC data was routinely collected on the following antibiotics: ampicillin, ceftiofur, chlortetracycline, clindamycin, danofloxacin, enrofloxacin, florfenicol, gentamicin, neomycin, oxytetracycline, penicillin, sulfadimethoxine, spectinomycin, tiamulin, tilmicosin, trimethoprim-sulfa (TMS), tulathromycin, and tylosin. MIC data was also obtained on gamithromycin and tildipirosin during the latter five years (2013 – 2017). Inclusion of the antibiotics in this study reflects laboratory standards and should not be perceived as an endorsement of their use in cattle. The prevalence of P. multocida, M. hemolytica, and B, trehalosi isolates will be described. For P. multocida isolates, the overall risk of resistance, and resistance patterns during 2008 – 2012 will be compared to 2013 – 2017. Commercially available software was used to build contingency tables and calculate relative risk (95% CI). Where cell values < 5, fishers exact test was used to compare proportions. Significance was set at α ≤ 0.05.


Prevalence of P. multocida, M. hemolytica, and B. trehalosi was 68%, 26%, and 7%, respectively from 3109 isolates. A total of 2106 P. multocida isolates with susceptibility result were further evaluated. For P. multocida, 10% (IQR 5, 26) of isolates were classified as resistant and at least one resistant isolate was detected for 22 of the 24 antibiotics routinely tested for susceptibility over the past 10 years. Five percent or less of the isolates were resistant to ceftiofur (< 1%), enrofloxacin (2%), chlortetracycline (2%), ampicillin (2%), danofloxacin (4%), florfenicol (5%), penicillin (5%), gentamicin (5%), TMS (5%). Resistance ranged from 8 – 36% for tulathromycin (8%), tiamulin (12%), gamithromycin (13%), tildipirosin (19%), spectinomycin (21%), tilmicosin (23%), oxytetracycline (36%), and sulfa (52%). Resistance was most common against clindamycin (98%), tylosin (88%), neomycin (55%), and sulfadimethoxine (52%).

When comparing  time periods, there were relatively fewer recent isolates resistant to ampicillin (RR: 0.22, 95% CI: 0.11, 0.44), ceftiofur (P = 0.05), florfenicol (RR: 0.61, 95% CI: 0.41, 0.88), gentamicin (RR: 0.45, 95% CI: 0.30, 0.66), sulfadimethoxine (RR: 0.81, 95% CI: 0.74, 0.87), tiamulin (RR: 0.25, 95% CI: 0.15, 0.41), and TMS (RR: 0.33, 95% CI: 0.22, 0.49). With the exception of danofloxacin (RR: 2.45, 95% CI: 1.50, 4.06), resistance to the other antibiotics was unchanged.


In conclusion, P. multocida is commonly isolated from bovine respiratory samples. For many of the drugs labeled for use in dairy cattle, resistance is relatively low and has either improved or at least remained constant. Veterinarians and producers should be aware of the pathogen challenges and work towards early detection, proper administration, and monitoring lung lesions to ensure that their treatment protocols improve lung health.

Comments/Suggestions/Problems should be directed to Steve Johnson

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