Antimicrobial Resistance of Staphylococci at Animal Human Interface in Smallholders and Dairy Farms in Central Oromia, Ethiopia

Abstract

Purpose

Staphylococcus species come from a variety of sources and can contaminate milk during milking, cause mastitis and other diseases in animals and humans. The enterotoxins they produce cause food poisoning. Our objectives were to isolate, biochemically characterize, and determine antimicrobial susceptibility profiles of Staphylococcus species from dairy farms in central Oromia, Ethiopia.

Methods

A total of 339 samples (n = 135 [raw milk], n = 135 [udders’ swabs], n = 25 [milkers’ hands swabs], n = 44 [pooled milking utensils’ swabs]) were collected from smallholders and dairy farms. Bacteriological culture and biochemical tests were performed to isolate and identify Staphylococcus species, and the Kirby Bauer disk diffusion method was used for antimicrobial susceptibility testing.

Results

Across all sample types and dairy farms, 247 (72.9%) Staphylococcus isolates were obtained which comprised of 101 (74.8%) isolates from raw milk, 98 (72.6%) from udder swabs, 30 (68.2%) from pooled utensil swabs, and 18 (72%) from milkers’ hand swabs. Fifty coagulase-positive Staphylococcus isolates (20 S. aureus, 20 S. hyicus and 10 S. intermedius) subjected to antimicrobial susceptibility tests have shown various degrees of resistance. All S. aureus isolates were 100% resistant to ampicillin and penicillin. Out of 20 S. hyicus isolates, 90% were resistant to ampicillin and 85% to penicillin. S. intermedius isolates (n=10) were 70% resistant to nalidixic acid and penicillin whilst remaining 100% resistant to ampicillin. Five S. aureus, three S. intermedius and two S. hyicus isolates from raw milk, milk utensil swabs and milkers’ hand swabs were multidrug-resistant (resistance to at least three classes of antimicrobials).

Conclusion

This study revealed a high prevalence of staphylococci in the dairy cattle, milkers and milking utensils with multidrug-resistant coagulase-positive Staphylococcus species suggesting the significance of pasteurization. Further research is encouraged on the factors leading to antibiotic resistance in Staphylococcus species.

Keywords:

• antimicrobial susceptibility profile
• cattle
• dairy farms
• smallholders
• Staphylococcus species

Abbreviations

BHI, brain heart infusion; CNS, coagulase-negative Staphylococcus; CPS, coagulase-positive Staphylococcus; MSA, mannitol salt agar; PAB, purple agar base; SFD, staphylococcal foodborne disease.

Data Sharing Statement

The corresponding author and first author will provide datasets that support the results of this article upon reasonable request.

Ethics Approval and Consent to Participate

We confirm that the animals were handled with the best practice of veterinary care. We also confirm that verbal informed consent was acceptable and approved by the College of Veterinary Medicine and Agriculture, Addis Ababa University. The study’s aims and methods were explained to all participating farm owners. The information utilized in this study was acquired from the participants and coded to maintain confidentiality after getting a verbal agreement. Ethical clearance for the study was obtained from the College of Veterinary Medicine and Agriculture, Addis Ababa University (AAU, CVMA), minutes of the Animal Research Ethics and Review Committee (Min NO: VM/ERC/04/10/14, Review Date: 23/10/2014).

Acknowledgments

We would like to thank Addis Ababa University, Thematic Research Fund for its financial support. We would also like to thank the cattle owners, the veterinarians, and the staff of the Ambo University department of Veterinary Laboratory Technology for their help in this study. The study was the first author’s master’s thesis presented to Addis Ababa University, College of Veterinary Medicine, and Agriculture, and it can be found online in the Addis Ababa University Institutional thesis repository. It was part of the thematic research project funded by Addis Ababa University, College of Veterinary Medicine and Agriculture, and all co-authors contributed significantly to the research work. We would like to confirm that the thesis work or part of it has not been submitted nor published in any journal. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture (USDA). USDA is an equal opportunity provider and employer.

Disclosure

The authors declare that there are no conflicts of interest regarding the publication of this paper.

Additional information

Funding

This work was supported by Addis Ababa University, Thematic Research Fund. The fund supporter had no role in research design, data collection, and analysis.