Abstract:
BACKGROUND : Respiratory tract infections (RTIs) associated with Pasteurella multocida,
Bordetella bronchiseptica, Streptococci, Staphylococci, and Pseudomonas species
have been reported in dogs. The objective of this study was to investigate the occurrence
and predictors of bacterial RTIs and antimicrobial resistance among samples from dogs
with lower RTIs at a referral veterinary teaching hospital in South Africa.
METHODS : Records of 157 dogs with lower RTIs presented to the veterinary
teaching hospital between 2007 and 2013 were included in the study. Crude and
factor-specific proportions of RTIs and antimicrobial resistance by breed, season, year,
sex, age category, and specimen type were computed. Chi-square or Fisher’s exact
tests were used to compare proportions of RTIs and antimicrobial resistant isolates
across categorical variables. Associations between breed, season, year, sex, age,
specimen, and odds of RTIs or multidrug resistance were assessed using Generalized
Estimating Equations.
RESULTS : There was only one sample per clinical case and bacterial RTIs were
observed in 53.5% of the samples tested. Pasteurella species (23.5%) were more
common than other species. Almost all (99.5%) isolates were resistant to at least one
antimicrobial, while 64.7% were multidrug resistant (MDR). Additionally, 17.0% and
3.3% showed evidence of extensive drug resistance (XDR) and pan-drug resistance
(PDR), respectively. The majority of MDR isolates were resistant to penicillin-G (90.9%),
lincomycin (100%), tylosine (75.8%), lincospectin (73.7%), ampicillin (72.5%), and
kanamycin (68.4%). None of the investigated predictors had significant association with
RTIs or antimicrobial resistance.
CONCLUSION : Pasturella species were the most common causes of RTIs. The high
levels of MDR and the presence of both XDR and PDR isolates raise the question of
the effectiveness of the current antimicrobial therapy used in patients with RTIs in referral
hospitals. Given the high level of resistance observed in this study, it is advisable that the
choice of antimicrobials for treatment of RTIs be based on antibiograms. This will ensure
use of the most efficacious antimicrobials and will minimize treatment failures among
cases presented with RTIs.
