Prevalence of Virulence Genes, Agr and Antimicrobial Resistance of Staphylococcus Aureus Isolated From Food and Dairy Products in Hamadan, Iran



Kazemian H² ; Tabar ZK¹ ; Hosseini SM¹
Source: Der Pharmacia Lettre Published:2016

Abstract

Staphylococcus aureus is one of the most important foodborne pathogen in food products. Exfoliative toxins (ETs) and toxic shock syndrome toxin-1(TSST-1) are important virulence factors that facilitate bacterial attack and reproduction in the body of host. Expression of exfoliative toxins controlled by accessory gene regulator (age) locus. Therefore, the identification of these genes in Staphylococcus aureus in food samples of very necessary and important. The aim of this study was prevalence of virulence genes (tsst1 and ETs) and agr of Staphylococcus aureus isolated from food products and association of these genes with antibiotic resistance. Between 2013 and 2014, 1050 food samples of various origin purchased and collected in Hamadan province in Iran. The S. aureus strains were isolated from raw milk and dairy products (n= 671) and raw meats (n=379). Samples were examined for the presence of S. aureus. Strains were characterized using standard microbiological procedures. Molecular identification of S. aureus strains confirmed by PCR. All isolates were screened for tsst1, agr, eta genes by PCR amplification. Out of 1050 samples, 98 (9.33%) samples were positive for S. aureus, including 36 (9.49%) of 379 raw meats and 62 (7.2%) of 671 raw milk and dairy products. The most frequent resistance was observed to erythromycin (30.6%), followed by tetracycline (29.6%), Gentamicin (27.6%), Clindamycin (26.5%), Ciprofloxacin(24.5%), Rifampin (24.5%), Sulfamethoxazole/ Trimethoprim (14.3%), and Cefoxitin (6.1%). The TSST-1 was identified in 30.61 percent of isolates, while the eta and etd were found in 63.26 and 75.51 percent of isolates, respectively. The distribution of agrA and agrC genes among the 98 food isolates were 63.26 and 14.28 percent, respectively. The detection of the high prevalence rate of virulence genes in this study indicates a potential risk for causing animal originated food poisoning that is a serious problem for public health. Infected animals and acquisition of infection during the processing stage are the main causes of contamination with S. aureus. Therefore, continuous surveillance is essential for monitoring of pathogens that are capable of causing food poisoning.