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Resistance of coagulase-negative staphylococci isolated from sheep to various antimicrobial agents
1Department of Farm Animal and Equine Medicine and Surgery, Boltons Park, Potters Bar.
Abstract:
Staphylococcal resistance to a variety of antimicrobial agents, defined as inhibition of bacteria growth in the presence of an antimicrobial agent, was approximately 75 per cent among coagulase-negative staphylococci isolated from milk and the teat skin of sheep. Resistance to broad spectrum antibiotics such as chloramphenicol and tetracycline as well as resistance to the combination of trimethoprim/sulphamethoxazole commonly used for the treatment of animals, was high in both groups of isolates. Four isolates of Staphylococcus epidermidis and three Staph xylosus isolated from the milk of dairy ewes were resistant to methicillin. Methicillin resistance is prevalent among human staphylococcal isolates and resistance to this antibiotic may reflect human handling of sheep.
Insights
Staphylococcal resistance to antimicrobials is high in sheep milk and teat skin bacteria. Methicillin resistance in some isolates may indicate transmission from human handlers.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Sheep Health
Background:
- Coagulase-negative staphylococci (CoNS) are significant pathogens in both human and animal health.
- Antimicrobial resistance in staphylococci poses a growing threat to effective treatment strategies.
- Sheep, particularly dairy ewes, can harbor staphylococcal populations that may be exposed to antimicrobials.
Purpose of the Study:
- To investigate the prevalence of antimicrobial resistance in staphylococci isolated from dairy sheep.
- To determine the level of resistance to commonly used antibiotics in these isolates.
- To identify potential links between sheep and human staphylococcal resistance patterns.
Main Methods:
- Isolation and identification of staphylococci from milk and teat skin samples of sheep.
- Antimicrobial susceptibility testing using a panel of relevant antibiotics.
- Phenotypic characterization of resistance, including methicillin resistance.
Main Results:
- Approximately 75% of coagulase-negative staphylococci exhibited antimicrobial resistance.
- High resistance rates were observed for chloramphenicol, tetracycline, and trimethoprim/sulphamethoxazole.
- Methicillin resistance was detected in four Staphylococcus epidermidis and three Staphylococcus xylosus isolates from milk.
Conclusions:
- Staphylococci from dairy sheep demonstrate substantial resistance to multiple antimicrobial agents.
- The presence of methicillin resistance in sheep isolates warrants further investigation into potential zoonotic implications.
- Findings suggest a possible role of human handling in the dissemination of resistant staphylococci among sheep.