Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains

This study evaluated the microbiological quality, presence of virulence genes, and antimicrobial resistance of <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> in sheep and goat milk and traditional Romanian dairy products (Telemea and Burduf cheeses). Raw milk contained high levels of coagulase-positive staphylococci (CPS; 5.2 log CFU/mL) and <i>E. coli</i> (4.3 log CFU/mL), with several samples exceeding legal limits. Sour cream exhibited moderate CPS (1.2-1.9 log CFU/g) and <i>E. coli</i> (0.4-3.12 log CFU/g) counts, with occasional non-compliance. Cheeses had low CPS (0.52-0.84 log CFU/g) and <i>E. coli</i> (0.37-0.89 log CFU/g) levels, all within permissible limits. Molecular analysis detected the <i>nuc</i> gene in 21 sheep milk samples, of which 85.7% also carried the <i>sea</i> gene and 14.3% carried <i>seb</i>. Additionally, two goat milk samples tested positive for both <i>nuc</i> and <i>sea</i>. Three Telemea cheese samples were also <i>sea</i>-positive. Among raw milk samples, 10 <i>E. coli</i> isolates carried <i>stx1</i>, and two additionally harbored <i>hly</i>, while dairy products were negative for <i>E. coli</i> virulence genes. Antimicrobial susceptibility testing showed high resistance of <i>S. aureus</i> to penicillin (90.5%) and ampicillin (85.7%), with multidrug resistance among <i>sea</i>- and <i>seb</i>-positive isolates. STEC isolates showed resistance to ampicillin (70%), tetracycline (50%), and trimethoprim-sulfamethoxazole (40%), but remained susceptible to amoxicillin-clavulanic acid.