The present study investigates the prevalence and etiology of subclinical mastitis in Țurcana sheep flocks located in south-western Romania. Milchtest and California Mastitis Test (CMT), were used for the detection of subclinical mastitis. A number of 360 milk samples across three lactation phases were analyzed. Subclinical mastitis was identified in 146 (40.6%) of sheep milk samples. Only milk samples (n = 146) collected from sheep diagnosed with subclinical mastitis were considered for microbiological analyses. Thus, Staphylococcus aureus (129/146; 88.4%) was identified as the predominant pathogen followed by Streptococcus spp. (14/146; 9.6%) Enterococcus spp. (7/146; 4.8%), Pseudomonas aeruginosa (6/146; 4.1%) and Klebsiella pneumoniae (5/146; 3.4%). Antimicrobial susceptibility of isolated strains of Staphylococcus aureus, Streptococcus spp. and Enterococcus spp. was also tested. The results showed varying resistance patterns depending on the farm and microorganism. In heard A the highest resistance of Staphylococcus aureus was identified to polymyxin B (79.7%) followed by novobiocin (73.4%) and tetracycline (45.3%); Streptococcus spp. to streptomycin (100%), novobiocin (100%), tetracycline (100%) and Enterococcus spp. to tylosin (100%), streptomycin (75.0%) and tetracycline (75.0%). In herd B, Staphylococcus aureus showed high resistance rates to polymyxin B (86.3%), novobiocin (74.5%) and cloxacillin (39.2%); Streptococcus spp. strains to streptomycin (100%), novobiocin (100%), tetracycline (100%) and Enterococcus spp. to gentamicin (100%), streptomycin (66.7%) and erythromycin (66.7%). The obtained preliminary results indicate a potential risk that future treatments of sheep mastitis may not be effective, and demonstrated that raw unpasteurized milk can harbor antimicrobial resistance pathogens posing a threat to public health. However, further investigations involving molecular research on resistance genes are required to draw comprehensive conclusions.
Keywords: Antimicrobial resistance; Foodborne bacteria; Milk; Romania; Sheep; Țurcana breed.
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