Quorum-sensing system of Staphylococcus aureus isolates from diabetic foot ulcers

Foot ulceration is a major complication of diabetes. Several microorganisms can colonize these wounds, being Staphylococcus aureus frequently isolated. It produces numerous virulence factors controlled by Quorum-sensing system, encoded by agr (accessory gene regulator). Currently four distinct genetic agr groups have been established. Quorum-sensing system of a collection of 23 S. aureus DFU isolates was characterized. agr type was evaluated by PCR, and gene copy number by absolute quantification with qPCR. The occurrence of alterations in agr copy numbers in S. aureus from polymicrobial infections was evaluated. Presence of mecA and mecC genes, responsible for methicillin resistance, was studied. It was possible to detect agrI and agrII in 52.2% and 39.1% of the isolates, respectively. In two isolates it was not possible to identify any agr type, and types III and IV were not detected. Copy number obtained ranged from 7.1 to 94279 copies of total gDNA and from 72.9 to 1487.9 copies of total gDNA. Variation in agr copy number of S. aureus from polymicrobial infections was observed. mecA occurred in 35% of the isolates, yet none tested positive for mecC. In conclusion, results show that agr type varies among DFU isolates and that agrI has a higher variance between copy numbers, in comparison with agrII, which may be related with a higher production of virulence factors. However, more studies targeting the characterization and variations of S. aureus DFU isolates agr system are still required in order to assess their impact in wounds prognostic and establishment of therapeutic protocols.