mecA and mecC Positive Strains of Staphylococcus aureus Detected and Isolated from Raw Milk of Ecuador

<b>Background</b>: Milk is a highly nutritious food, but its composition makes it an ideal medium for microbial growth, particularly for bacteria like <i>Staphylococcus aureus</i> (<i>S. aureus</i>). In Ecuador, raw milk consumption is culturally rooted, and contamination risks are heightened, especially in informal markets. <i>Staphylococcus aureus</i>, a Gram-positive, coagulase-positive bacterium, commonly colonizes mucous membranes and can cause a range of infections due to its production of thermostable toxins. Its impact extends to bovine mastitis, severely affecting dairy production. Of particular concern is the emergence of methicillin-resistant <i>S. aureus</i> (MRSA) strains, associated with the acquisition of the <i>mecA</i> gene located on the "staphylococcal chromosomal cassette mec" (SCCmec) element and identification of a <i>mecA</i> homologue, <i>mecC</i>, further complicates detection and monitoring efforts. <b>Objectives</b>: This study evaluated the prevalence of <i>S. aureus</i> and MRSA strains in raw milk from Ecuadorian provinces Pichincha and Manabí. <b>Methods</b>: A total of 633 samples were collected and analyzed via real-time PCR (qPCR) and bacterial isolation methods, complemented by endpoint PCR assays for <i>mecA</i> and <i>mecC</i> genes detection. <b>Results</b>: A high prevalence of <i>S. aureus</i> (84%) was observed, with significant differences between regions. MRSA was detected in 23% of all samples, with <i>mecA</i> being more prevalent than <i>mecC</i> among isolates. Sequencing of <i>16S rDNA</i> confirmed the identity of isolates, while phylogenetic analysis of <i>mecA</i> and <i>mecC</i> genes validated their presence. The findings suggest that suboptimal hygiene practices and varied biosecurity protocols, especially among small and medium dairy producers, may contribute to the persistence of resistant strains. <b>Conclusions</b>: This study highlights the presence of <i>S. aureus</i> and MRSA in raw milk, underscoring the need for strengthened surveillance, improved hygiene practices, the use of molecular diagnostic tools, and proper heat treatments to reduce the public health risks associated with contaminated milk and its derivatives.