Relationship of the accessory regulator gene (agr) with multiresistance in Staphylococcus aureus strains isolated from hospitals and dental offices

Inert surfaces favor the persistence of Staphylococcus aureus, as they are reservoirs and means of contamination in hospital and clinical environments. The pathogenicity of this bacterium is controlled by the accessory gene regulatory (agr) system. We examined virulence and toxin genes in isolated strains of S. aureus on inert surfaces and their relationship with the mecA gene, responsible for methicillin resistance (MRSA) in 59 S. aureus strains isolated from inert surfaces and stored in the molecular biology laboratory of the Catholic University of Cuenca, in which presence of toxin genes (lukS/lukF-PV, tst) and the mecA gene had been previously detected. Multiplex PCR was used to determine the agr types. Of the 59 S. aureus strains, 66.1% were positive for agrI, 8.5%, agrII, and 18.6%, agrIII; agrIV was not present in any of the strains. A significant relationship was found between agrI and MRSA. Molecular agr gene typing is important for monitoring the appearance, dissemination, and persistence of MRSA epidemic strains. In conclusion, the gene with the highest frequency was agrI followed by agrIII and agrII.