Genetic Polymorphism of agr Locus and Antibiotic Resistance of Staphylococcus aureus at two hospitals in Pakistan

OBJECTIVE The accessory gene regulator (agr) locus in Staphylococcus aureus (S. aureus) is a global regulator of quorum sensing and controls the production of virulence factors. This study was carried out to investigate the agr specific groups both in methicillin resistant and sensitive Staphylococcus aureus (MRSA and MSSA) and their relation with antibiotic resistance. METHODS A total of 90 clinical S. aureus isolates were studied from two tertiary care hospitals. The isolates were identified by standard biochemical tests. Methicillin resistance was confirmed by oxacillin and cefoxitin resistance. Multiplex PCR was used to determine the agr groups. RESULTS MRSA prevalence was found to be 53.3%.The agr groups' distribution in MRSA was as follows: 22 (45.8%) belonged to group I, 14 (29.1%) belonged to group III and 2 (4.1%) belonged to group II. agrIV was not detected in MRSA. For 17 isolates, the agr group was not detected.agr III isolates showed higher antibiotic resistance than agrI isolates except in case of oxacillin and linezolid. CONCLUSIONS Strict infection control policy and antibiotic guidelines should be adopted to control the problem of MRSA. Higher prevalence of agr I and agr III shows that they are dominant agr groups of our area.