Detection of Enterotoxin Genes and Methicillin-Resistance in Staphylococcus aureus Isolated from Water Buffalo Milk and Dairy Products

Abstract

The aim of this study was to analyze the presence of genes encoding staphylococcal enterotoxins and methicillin resistance in Staphylococcus aureus isolates obtained from water buffalo milk and dairy products. A total of 200 samples (100 raw milk, 50 clotted cream, and 50 cheese samples) was collected from different dairy farms and smallholders in Samsun, Turkey. All samples were analyzed using the standard procedure EN ISO 6888-1 and isolates were confirmed for the presence of the target 16S rRNA specific for Staphylococcus genus specific and nuc gene specific for S. aureus species by PCR. S. aureus was identified in 30 of 100 milk (30%), 9 of 50 clotted cream (18%), and 17 of 50 cheese (34%) samples. A total of 99 isolates was confirmed as S. aureus. Genotypic methicillin resistance was evaluated using PCR for the mecA gene. Out of 99 isolates, nine (9%) were found to be methicillin resistant (mecA gene positive). Twelve out of 99 (12%) S. aureus isolates were found positive for one or more genes encoding the enterotoxins. The gene coding for enterotoxin, sea, was the most frequent (five isolates,41.6%), followed by sec (two isolates, 16.6%), sed (1 isolates, 8.3%) and see (1 isolate, 8.3%). While three isolates (25%) contained both sec and sed, none of the samples was positive for seb. In conclusion, the presence of se gene-positive and methicillin-resistant S. aureus in buffalo milk and products revealed that consumption of these products is a potential risk of foodborne infection in this region. Practical ApplicationEnterotoxigenicand methicillin-resistant S.aureus(MRSA) in milk and dairy products is animportant public health problem. Especially in traditional dairy products, Staphylococcal enterotoxins may cause food poisoning due to consumption of raw or unpasteurized milk products.