Accessory gene regulator (agr) typing of Staphylococcus aureus isolated from human infections.

Staphylococcus aureus is a major hospital and community acquired pathogen. A total of one hundred strains were investigated. They were collected from January 2004 to July 2006 in the laboratory of microbiology at Charles Nicolle University hospital of Tunis. The isolates were identified by conventional methods. Methicillin resistance was confirmed by amplification of mecA gene by PCR. The agr groups were identified by multiplex PCR. The agr groups were distributed as follows: 19 strains belonged to group I, 16 to group II and 65 to group III. Among methicillin resistant S. aureus (MRSA), 9 (16.4%) belonged to group 1, 8 (14.5%) to group II and 38 (69.1%) to group IlI. For methicillin susceptible S. aureus (MSSA), only 10 strains (22.2%) belonged to group I, 8 (17.8%) to group II and 27 (60%) to group III. A preferential link was observed between agr group I and invasive infections (P=0.003) especially bacteremia (P=10(-4). Besides, agr groups II and III were closely related with non invasive infections (P=0.003). No association was found between other types of infections and agr groups. Likewise, no correlation was observed between agr groups, age or sex of patients and type of infections.