Abstract
Simple SummaryThis work investigated the presence of staphylococci resistant to antibiotics in the raw milk produced in sheep farms, which is intended for human consumption, in an extensive study performed throughout Greece. In 31% of flocks, staphylococci resistant to at least one antibiotic were recovered; in 12% of flocks, staphylococci resistant to at least three different antibiotic classes were found. Factors potentially associated with recovery of resistant isolates were the lack of experience by farmers (<5 years), the period immediately post lambing, and the intensive management system applied in the flocks.The objectives of this work were to study prevalence and characteristics of resistance to antibiotics of staphylococcal isolates from the bulk-tank milk of sheep flocks across Greece, to assess possible associations of the presence of antibiotic resistance with the quality of milk in these flocks and to evaluate flock-related factors potentially associated with antibiotic resistance among these isolates. A cross-sectional study was performed in 325 sheep flocks in Greece. Bulk-tank milk samples were collected for bacteriological examination; staphylococcal isolates were evaluated for resistance to 20 antibiotics. Oxacillin-resistant staphylococcal isolates, isolates resistant to any antibiotic, and multi-resistant isolates were recovered from 8.0%, 30.5%, and 12.0% of flocks, respectively. Of 232 isolates, 11.6% were resistant to oxacillin, 46.1% were resistant to at least one antibiotic, and 16.4% were multi-resistant. Resistance was seen more frequently among coagulase-negative (50.6%) than among Staphylococcus aureus (31.5%) isolates. Resistance was more frequent against penicillin and ampicillin (34.1% of isolates), clindamycin (17.7%), and fosfomycin (14.2%). An association was found between biofilm formation by staphylococci and resistance to fosfomycin. For recovery of oxacillin-resistant isolates, the lack of experience by farmers emerged as a significant factor; respective factors for the isolation of staphylococci resistant to any antibiotic or multi-resistant isolates were the early stage of the lactation period (0th–1st month) and the intensive management system applied in the flocks, respectively.
Highlights
Sheep farming for milk production is an important sector of the Greek agricultural industry
Staphylococci were recovered from bulk-tank milk samples from 206 flocks (63.4%, 95% confidence intervals (CI): 58.0–68.4%) (Staphylococcus aureus and coagulase-negative staphylococci were isolated from samples from 54 (16.6%) and 164 (50.5%) flocks, respectively)
The presence of resistant staphylococcal isolates in the milk produced for human consumption on sheep farms raises issues within the ‘one health’ concept
Summary
Sheep farming for milk production is an important sector of the Greek agricultural industry. The country has a significant annual sheep milk production, which amounted to. 639,165,000 L in 2019 [1] This quantity accounts for around 20% of European and 7% of world sheep milk production [2]. Sheep milk is used for cheese production. Various cheese types are produced from sheep milk, and an important proportion (e.g., ‘feta’ cheese) is exported, highlighting the international significance of sheep milk production in Greece. The quality of raw milk is important, as it contributes to the quality of cheese produced, which has a significance for public health. Among the various factors that account for milk quality of raw milk are antibiotic-resistant bacteria
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