Surveying Contamination Rate of Local Lactic cheese with Escherichia coli, Staphylococcus aureus and Listeria monocytogenes in Gorgan in 2017

Lactic cheese is traditionally produced from raw milk in some provinces of Iran. Therefore, presence of pathogenic bacteria in these cheeses can be dangerous to human health. The aim of this study was to evaluate the contamination rate of local lactic cheeses produced in Gorgan with Escherichia coli, Staphylococcus aureus and Listeria monocytogenes.

Cheese samples were randomly collected from 5 supply centers of this product in Gorgan. The samples were transferred to sterile containers with dry ice to the Microbiology Laboratory of Gorgan Islamic Azad University. After enrichment in specific media, they were cultured in selective media according to standard methods.

In this study, 40 samples of lactating cheeses of bovine and sheep and 5 samples of pasteurized bovine cheeses were evaluated for possible contamination. According to the results, out of 20 cow cheese samples, only 2 (10%) and out of 20 sheep cheese samples, 6 ones (30%) were infected with Escherichia coli. Coagulase positive Staphylococcus aureus was observed in 3 samples of cow cheese (15%) and 5 sheep cheese samples (25%). Listeria monocytogenes was not detected in any of the cheese samples. Industrial pasteurized samples were also not contaminated with any of the bacteria studied.

The results showed that sheep cheeses were more contaminated to Escherichia coli and Staphylococcus aureus compared to cow cheeses. Considering the presence of Escherichia coli and Staphylococcus aureus in some local lactic cheeses supplied in Gorgan, it is necessary to consider hygienic actions more seriously and the use of pasteurized milk is recommended for production of mentioned cheeses.