Toxigenic genes of coagulase-negative staphylococci and staphylococcus aureus from milk and dairy

Abstract

The study investigates the prevalence of Staphylococcus aureus and coagulasenegative staphylococci in raw milk and dairy products and assesses their toxin -related pathogenic potential and methicillin resistance. A total of 1015, raw milk (260) and dairy samples (325 cheeses, 180 yogurts, 140 ice creams, 110 butter samples) were collected and analyzed. The prevalence of Staphylococcus aureus and coagulase-negative staphylococci were 3.2% and 5.3% with mean counts of 3.46 and 3.16 log CFU/mL-g, respectively. Three (sea, seb, see) of five (sea, seb, sec, sed, see) staphylococcal enterotoxin (SE) genes, two (tss, etb) of four (tss, pvl, eta, etb) virulence -associated genes, and the absence of methicillin resistance (mecA) gene were defined by polymerase chain reaction. SE sea (6.9%), seb (2.3%) and see (1.1%) genes were detected in Staphylococcus aureus from one milk and seven different cheese samples. The presence of multiple enterotoxin genes (sea and see) was detected in a Staphylococcus aureus isolate from one cheese. However, the milk -sourced one coagulase-negative staphylococci possessed both the tss and etb virulence genes. The finding in this study indicates that the frequency of coagulase-negative staphylococci was higher than Staphylococcus aureus and moreover, toxin genes associated with human infections were assigned in coagulase-negative staphylococci while enterotoxin genes were determined among Staphylococcus aureus. In terms of food safety perspective, coagulasenegative staphylococci are ignored and they are not considered in standard food surveillance analysis. But the presence of virulent coagulase-negative staphylococci in foods is a public health concern. The results obtained from this study are significant as it demonstrates that pathogenic coagulase-negative staphylococci are found in foods, and provides data from Turkey. Additional research is required concerning coagulase-negative staphylococci in the food matrix and clinical isolates.