A study of Staphylococcus aureus nasal carriage, antibacterial resistance and virulence factor encoding genes in a tertiary care hospital, Kayseri, Turkey

Abstract

Aim: This study was to determine the virulence encoding genes, and the antibiotic resistance patterns of the Staphylococcus aureus isolates, which were isolated from the nasal samples of chest clinic patients.
Materials and Methods: The nasal samples of the in‑patients (431) and out‑patients (1857) in Kayseri Training and Research Hospital’s Chest Clinic, Kayseri, Turkey, were cultured on CHROMagar (Biolife, Italiana) S. aureus, and subcultured on sheep blood agar for the isolation of S. aureus. Disc diffusion method was used for antimicrobial susceptibility testing. The occurrence of the staphylococcal virulence encoding genes (enterotoksins [sea, seb, sec, see, seg, seh, sei, sej], fibronectin‑binding proteins A, B [fnbA, fnbB], toxic shock syndrome toxin‑1 [tst]) were detected by polymerase chain reaction.
Results: Forty‑five of the 55 (81.8%) S. aureus isolates from inpatients, and 319 (90.6%) isolates from tested 352 out‑patient’s isolates were suspected to all the antibiotics tested. methicillin‑resistant S. aureus (MRSA) was detected in 1.2% of S. aureus isolates. Rifampin, trimethoprim‑sulfamethoxazole, clindamycin, erythromycin, gentamicin resistance rates were 1.2%, 1.7%, 2.0%, 8.8%, and 1.2%, respectively. The isolates were susceptible to teicoplanin and vancomycin. The genes most frequently found were tst (92.7%), seg (85.8%), sea (83.6%), fnbA (70.9%). There was no statistical significance detected between MRSA and mecA‑negative S. aureus isolates in encoding genes distribution (P > 0.05).
Conclusion: Our results show that virulence factor encoding genes were prevalent in patients with S. aureus carriage, whereas antibiotic resistance was low. These virulence determinants may increase the risk for subsequent invasive infections in carriers.

Key words: Carriage, Staphylococcus aureus, virulence factors