Molecular identification, virulence, and antibiotic-resistant genes characteristics of Staphylococcus spp., isolated from milk samples.

Background: Food safety and food-borne infections are major subjects of global interest. Dairy products are considered as important source for these infections.

Aim: The present study was conducted to identify the occurrence and to genotype isolates of Staphylococcus spp. recovered from milk samples in Al-Diwaniyah City, Iraq.

Methods: The current study included the collection of 50 milk samples purchased from local stores in the current city. These samples were subjected to bacterial cultivation and biochemical tests. Later, the growth was used to extract the genomic DNA that was exposed to PCR and partial gene sequencing both targeted the 16S rRNA gene at a specific genetic piece.

Results: The PCR results demonstrated the amplification of the genetic fragment of five genetic clusters for each of Staphylococcus aureus (SAD11, SAD12, SAD13, SAD14, and SAD15), Staphylococcus epidermidis (SED1, SED2, SED3, SED4, and SED5), and Staphylococcus intermedius (SID1, SID2, SID3, SID4, and SID5). The PCR products were sent out to sequencing and reported that the current isolates were similar in their genetic content with global isolates at 95.34% to 97.59%, 96.21% to 97.57%, and 96.09% to 97.88%, respectively, of identity.

Conclusion: The present findings show high genetic variations among isolates of S. aureus, S. epidermidis, and S. intermedius recovered from milk samples, and these genotypes are found in different infection settings related to humans and animals, which may pose high risks to humans and animals.