The relation between accessory gene regulator (agr) types of S.aureus and some phenotypic criteria

Staphylococcus aureus is a gram-positive bacterium that has remained a persistent pathogen, causing infections such as endocarditis and toxic shock syndrome in humans. The accessory gene regulator (agr) system of Staphylococcus aureus is responsible for controlling the expression of many genes that code virulence factors and hemolysis.This study was carried out to determine the S.aureus agr group based on their source of isolation and any relation between agr specificity groups, pigmentation and hemolysis. DNA of 194 S. aureus isolates were extracted by lysozym-phenol chloroform method, included 85clinical samples, 58 samples which isolated from nose of health care workers and 51 cases obtained from food product in Gorgan, North of Iran. PCR-based assays were used to evaluate agr locus nucleotide polymorphism for the identification of agr specificity group. Pigmentation on nutrient agar medium and hemolysis on sheep Blood agar medium were assessed. The majority of isolates belonged to agr group I (43/3%), followed by agr group III (28/87%), agr group II (22/68%), and agr group IV (5/15%). The isolates belonged to agr group IV have greater ability to produce hemolysin (% 60) whereas isolates belonged to agr group III have greater ability to produce pigment (% 60.5). agr group I was predominant among health care worker and food product specimens in Gorgan, North of Iran but in strains isolated from patient, agr group III was predominant. Investigation of the possible role of agr group III in Staphylococcus aureus infection in the next studies is recommended.