Frequency of Antimicrobial-Resistant Genes in Salmonella enteritidis Isolated from Traditional and Industrial Iranian White Cheeses

Abstract

Iranian white cheese is one of the most important kinds of cheese produced in large scale with high consumption in the country. This dairy product transmits bacterial pathogens like Salmonella spp. Antibiotic resistant Salmonella are widespread in the world. This study was performed to evaluate the frequency of antimicrobial-resistant Salmonella enteritidis and related genes isolated from traditional and industrial Iranian white cheeses. A total of 200 traditional and industrial Iranian white cheeses were collected within Chaharmahal Va Bakhtiari province (southwest Iran). After culturing on specific media using standard bacterial tests the Salmonella sp. was isolated. For specific detection of S. enteritidis from other Salmonella strains sefA gene was studied. Finally, the antibiotic susceptibility patterns were investigated. Results showed that 17 % of cheese samples were contaminated by Salmonella and 5.5 % of specimens by S. enteritidis. The frequencies of resistance genes including tetA, tetB, tetC, cat3, and floR in isolated S. enteritidis were 36.4, 54.5, 81.8, 54.5, and 36.4 %, respectively. All isolated S. enteritidis were susceptible to ciprofloxacin, cefotaxime, and ceftazidime (100 %). In addition, most of them were resistance to chloramphenicol (64 %) and susceptible to gentamicin (98 %). The Salmonella contamination was more frequent in traditional Iranian white cheeses (11.5 %) as compared to industrial (5.5 %) samples (p < 0.05). As compared to industrial samples, high level of resistant genes in Salmonella enteritidis isolated from traditional Iranian white cheeses were observed (p < 0.05). Therefore, traditional Iranian white cheeses are important source of Salmonella contamination in the country hence examination of dairy products for the presence of this pathogen is important.