Determination of the Presence of Salmonella spp., Antibiotic Resistance and Virulence Genes in Milk and Dairy Products

Abstract

Milk and dairy products are essential food sources in human nutrition but can serve as reservoirs for pathogenic bacteria, such as Salmonella spp., posing serious public health risks. The increasing emergence of antimicrobial resistance in foodborne pathogens further complicates food safety and infection control. This study aimed to determine the presence of Salmonella spp. in milk and dairy products, analyse the virulence genes of the isolates and evaluate their antibiotic resistance profiles. A total of 300 milk and dairy product samples (150 raw milk, 60 village cheese, 50 curd cheese and 40 butter) were collected from family businesses and local markets in Samsun, Turkey. Salmonella spp. was detected using ISO 6579 culture methods, and PCR was used to confirm the presence of the oriC gene. The virulence genes (invA, hilA, avrA and stn) were identified by PCR. Antibiotic resistance was assessed using the VITEK 2 AST-GN97 system. Salmonella spp. was detected in 12 of 300 samples (4%), with the highest prevalence in village cheese (8.3%). Among 36 isolates, all (100%) harboured invA and hilA, while avrA (63.8%) and stn (55.5%) were less frequent. All isolates were resistant to at least two antibiotics, with the highest resistance to ampicillin (100%). The presence of Salmonella spp. in milk and dairy products, along with high rates of antibiotic resistance, highlights the need for enhanced food safety regulations, improved hygiene standards and stricter antimicrobial stewardship. Implementing effective pasteurisation and hazard control measures is crucial to reducing contamination risks and protecting public health.