Staphylococcus aureus isolated from patients with recurrent furunculosis carrying Panton-Valentine leukocidin genes represent agr specificity group IV

Recurrent furunculosis (RF) caused by Staphylococcus aureus presents a difficult clinical problem and causes significant morbidity. The study aim was to characterise agr groups and detect toxin genes among S. aureus strains isolated from RF patients. Microbiological material was obtained from evacuated furuncules of 44 RF patients. Nasal swabs were obtained from both the RF patients and the controls (150 healthy volunteers with no history of RF). All strains were screened for the presence of lukS/lukF-PV, tst, sea, seb, sec, sed, eta, and etb genes. Moreover, agr specificity groups (I-IV) were identified. Antibiotic-susceptibility tests were performed by disk diffusion method and methicillin susceptibility was verified by mecA gene amplification. The investigated strains were resistant to penicillin, clindamycin, erythromycin, and tetracycline. All showed susceptibility to methicillin. Thirty-five of 44 strains tested were positive for leukocidin lukS/lukF-PV genes and 12/44 for enterotoxin seb gene. The coexistence of PVL genes and seb gene concerned 7/44 strains. The remaining toxin genes were not found. Forty-three strains belonged to agr specificity group IV including all strains with lukS/lukF-PV genes. Nasal carriage of S. aureus was observed in 27/44 (61.3%) RF patients and in 43/150 (28.6%) controls (p = 0.001). In all RF subjects, nasal strains did not differ from those isolated from furuncules in terms of lukS/lukF-PV gene status and agr specificity. To the best of our knowledge, it is the first study that shown such a predominance of agr group IV strains in RF patients.