Prevalence of agr specificity groups among Staphylococcus aureus strains isolated from different clinical specimens patients with cardiovascular surgery associated infections

Staphylococcus aureus is an extremely versatile pathogen responsible for a large spectrum of human diseases, ranging from skin infections and food poisoning to life-threatening nosocomial infections. S. aureus pathogenicity is a complex process involving a diverse array of virulence factors that are coordinately expressed during different stages of infection by a network of virulence regulators. The accessory gene regulator (agr) is one of these virulence regulators, being a quorum-sensing system activated by a bacterial-density-sensing peptide (autoinducing peptide - AIP). Different S. aureus strains produce AIPs with distinct structures, and strains can be grouped on this basis since they will activate the agr response of strains within the same group and inhibit the agr response of strains from different groups by competitive inhibition. The aim of this study was to investigate the potential associations between each agr group and a certain type of clinical sample by studying 88 S. aureus strains isolated from different clinical specimens from patients admitted in the Emergency Institute for Cardiovascular Diseases, Bucharest. A multiplex PCR was used to determine the agr groups among analyzed strains. The obtained results showed that agr III was the most prevalent group among the tested strains. The agr I was associated with strains isolated from blood cultures, whereas agr III prevailed among strains isolated from respiratory tract secretions. Although the obtained results do not allow us to establish a direct relationship between the agr group and type of S. aureus infection, but we can speculate that the preferential association between certain agr alleles and virulence factors may favour a more efficient activation of the virulence potential.