Abstract: Antimicrobial resistance limits traditional treatment options and increases costs. It is therefore important to estimate the magnitude of the problem so as to provide empirical data to guide control efforts. The aim of this study was to investigate the burden and patterns of antimicrobial resistance (AMR) among equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) from 1993 to 2009. Retrospective data of 1711 equine Staphylococcus samples submitted to the UKVDL during the time period 1993 to 2009 were included in the study. Antimicrobial susceptibility testing, that included 16 drugs, were performed using cultures followed by the Kirby-Bauer disk diffusion susceptibility test. The proportion of resistant isolates by animal breed, species of organism, sample source, and time period were computed. Chi-square and Cochran-Armitage trend tests were used to identify significant associations and temporal trends, respectively. Logistic regression models were used to investigate predictors of AMR and multidrug resistance (MDR). Results: A total of 66.3% of the isolates were resistant to at least one antimicrobial, most of which were Staphylococcus aureus (77.1%), while 25.0% were MDR. The highest level of resistance was to penicillins (52.9%). Among drug classes, isolates had the highest rate of AMR to at least one type of β-lactams (49.2%), followed by aminoglycosides (30.2%). Significant (p < 0.05) associations were observed between odds of AMR and horse breed, species of organism and year. Similarly, significant (p < 0.05) associations were identified between odds of MDR and breed and age. While some isolates had resistance to up to 12 antimicrobials, AMR profiles featuring single antimicrobials such as penicillin were more common than those with multiple antimicrobials. Conclusions: Demographic factors were significant predictors of AMR and MDR. The fact that some isolates had resistance to up to 12 of the 16 antimicrobials assessed is quite concerning. To address the high levels of AMR and MDR observed in this study, future studies will need to focus on antimicrobial prescription practices and education of both practitioners and animal owners on judicious use of antimicrobials to slow down the development of resistance.
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The study examines the prevalence and patterns of antimicrobial resistance (AMR) in equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory between 1993 and 2009. The findings indicate a high level of antimicrobial resistance, notably to penicillin, with demographic factors being significant in predicting the resistance rates.
Methodology
The study used data from 1711 equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) from 1993 to 2009.
Antimicrobial susceptibility tests were performed on 16 drugs using the Kirby-Bauer disk diffusion susceptibility test.
The researchers computed the proportion of resistant isolates by factors like animal breed, Staphylococcus species, the source of the sample, and time period.
Statistical tools like Chi-square and Cochran-Armitage trend tests were employed to identify significant associations and temporal trends.
Logistic regression models were used to investigate predictors of antimicrobial resistance (AMR) and multidrug resistance (MDR).
Results
A significant majority, 66.3% of the samples, were resistant to at least one antimicrobial, most of which belonged to Staphylococcus aureus.
About a quarter (25.0%) of the isolates were multidrug-resistant.
The highest level of resistance was observed for penicillin (52.9%). Among drug classes, the isolates showed the highest rate of resistance to β-lactams (49.2%) and aminoglycosides (30.2%).
Factors like horse breed, Staphylococcus species, and year correlated significantly with the odds of AMR and MDR.
While some isolates showed resistance to 12 out of the 16 antimicrobials, resistance profiles featuring single antimicrobials, such as penicillin, were more common.
Conclusions
The study concludes that demographic factors are significant predictors of AMR and MDR.
The researchers bring attention to the concerning fact that some isolates displayed resistance to as many as 12 out of 16 antimicrobials tested.
The study suggests that future research should focus on prescription practices and education of practitioners and animal owners about judicious use of antimicrobials to slow down the development of resistance.
Cite This Article
APA
Adams R, Smith J, Locke S, Phillips E, Erol E, Carter C, Odoi A.
(2018).
An epidemiologic study of antimicrobial resistance of Staphylococcus species isolated from equine samples submitted to a diagnostic laboratory.
BMC Vet Res, 14(1), 42.
https://doi.org/10.1186/s12917-018-1367-6
Department of Biomedical and Diagnostic Sciences, University of Tennessee, College of Veterinary Medicine, 2407 River Dr., Knoxville, TN, 37996, USA.
Smith, Jackie
University of Kentucky, Veterinary Diagnostic Laboratory, 1490 Bull Lea Rd., Lexington, KY, 40511, USA.
Locke, Stephen
University of Kentucky, Veterinary Diagnostic Laboratory, 1490 Bull Lea Rd., Lexington, KY, 40511, USA.
Phillips, Erica
University of Kentucky, Veterinary Diagnostic Laboratory, 1490 Bull Lea Rd., Lexington, KY, 40511, USA.
Erol, Erdal
University of Kentucky, Veterinary Diagnostic Laboratory, 1490 Bull Lea Rd., Lexington, KY, 40511, USA.
Carter, Craig
University of Kentucky, Veterinary Diagnostic Laboratory, 1490 Bull Lea Rd., Lexington, KY, 40511, USA.
Odoi, Agricola
Department of Biomedical and Diagnostic Sciences, University of Tennessee, College of Veterinary Medicine, 2407 River Dr., Knoxville, TN, 37996, USA. aodoi@utk.edu.
MeSH Terms
Age Factors
Animals
Anti-Bacterial Agents
Drug Resistance, Bacterial
Drug Resistance, Multiple, Bacterial
Female
Horse Diseases / epidemiology
Horse Diseases / microbiology
Horses
Kentucky / epidemiology
Male
Microbial Sensitivity Tests
Retrospective Studies
Staphylococcal Infections / epidemiology
Staphylococcal Infections / microbiology
Staphylococcal Infections / veterinary
Staphylococcus / classification
Staphylococcus / drug effects
Staphylococcus / isolation & purification
Grant Funding
N/A / University of Tennessee Center of Excellence in Livestock Diseases and Human Health (COE) Research Award
Conflict of Interest Statement
ETHICS APPROVAL: This study was approved by the University of Tennessee Institutional Animal Care & Use Committee (IACUC). The study used retrospective laboratory records and did not involve animals. All data were handled in compliance with relevant guidelines. No field studies or experiments were conducted as part of this study and hence no informed consent was required. CONSENT FOR PUBLICATION: Not Applicable. COMPETING INTERESTS: The authors declare that they have no competing interests. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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