Survey on the contamination rate and determination of antibiotic resistance of Staphylococcus aureus, Escherichia coli and Salmonella strains isolated from traditional cheeses distributed in Mahabad, Iran

Traditional cheese has desirable organoleptic characteristics for Iranian consumers. Escherichia coli, Staphylococcus aureus and Salmonella are some of the most important microbial agents in food poisoning and gastrointestinal infections, which can contaminate this product and endanger the health of consumers. The aim of this study was to survey the contamination rate and determination of antibiotic resistance of Staphylococcus aureus, Escherichia coli and Salmonella strains isolated from traditional cheeses distributed in Mahabad, Iran. In a cross-sectional study, 100 samples of traditional cheese from the production and distribution centers in Mahabad city were randomly selected in 2016 to determine the bacterial contamination in accordance to national standard guidelines for the presence of Staphylococcus aureus, E.coli and Salmonella spp. Anti-biograms test was conducted using a standard disc diffusion method through the measurement of the inhibitory zone diameter on the Muller Hinton agar. Among the 100 samples, 54, 45 and 0 samples were positive for Escherichia coli, Staphylococcus aureus and Salmonella, respectively. All E.coli (100%) were found to be resistant to Amoxicillin, while Staphylococcus aureus isolates (100%) were resistant to Amoxicillin-Clavulanic acid and Amoxicillin. However, 66.6% isolates of E.coli were susceptible to Ceftriaxone and 97.7% isolates of Staphylococcus aureus were susceptible to Trimethoprim – Sulfamethoxazole. The microbial quality of traditional cheeses distributed in Mahabad city was not evaluated as appropriate and the values did not meet the national standards. Thus, further monitoring and control are needed.