RESUMO
BACKGROUND: The inhibitory activities of vitamins K2 against clinical isolates of quinolone-resistant and methicillin-resistant Staphylococcus aureus (QR-MRSA) are unclear. The main aim is to better understand of inhibitory activities of vitamins K2, multi-locus sequence typing (MLST), SCCmec, and spa typing in clinical isolates of QR-MRSA on those mutation and gene expressions. MATERIALS AND METHODS: After collecting S. aureus clinical isolates and detecting QR-MRSA, the genes encoding norA, grlA, grlB, gyrA, and gyrB were sequenced. After treating isolates by vitamin K2, isolates were prepared to measure norA, grlA, grlB, gyrA, and gyrB gene expression. The quantitative-real-time PCR was used to measure the expression of efflux pump genes. RESULTS: QR-MRSA, MDR, and XDR strains were reported in 59.4%, 73.9%, and 37.6% of isolates, respectability. SCCmecIV (36.5%) and SCCmecV (26.8%) had the highest frequency. Thirty-nine spa types were identified, t021, t044, and t267 types most prevalent in QR-MRSA isolates. ST22 and ST30 dominated the invasive, drug-resistant isolates and QR-MRSA. In 24 h incubated isolates, the most noticeable change of gene expression with vitamin K2 was that the norA, gyrA, and grlB genes were highly repressed. However, the down-regulation of grlA at 24 h after being treated by vitamin K2 was more than another gene. Further, a significant decrease was observed in QR-MRSA-treated isolates compared to un-treated isolates. In other words, norA, grlA, grlB, gyrA, and gyrB genes were less suppressed by QR-MRSA (p ≤ 0.01, p ≤ 0.05). CONCLUSION: Vitamin K2 has significant inhibitory effects on the genes responsible for resistance to fluoroquinolone antibiotics. However, a subminimum inhibitory concentration (sub-MIC) level of vitamin K2 was delayed but did not completely inhibit norA, grlA, grlB, gyrA, and gyrB genes in MRSA strains.
