Fluoroquinolone resistance of Staphylococcus epidermidis isolated from healthy conjunctiva and analysis of their mutations in quinolone-resistance determining region

Abstract

AbstractBackgroundStaphylococcus epidermidisis the most common pathogen in postoperative endophthalmitis and causes various infectious eye diseases. However, there is very little information on fluoroquinolone antibiotic resistance toS. epidermidisidentified in conjunctival microbe and analysis of related genes. Here, the authors investigated the rate of resistance to fluoroquinolones ofStaphylococcus epidermidisisolated from normal conjunctival microbes and mutations in the quinolone-resistance determining region (QRDR).Methods377 eye samples from 187 patients who underwent intravitreal injection and cataract surgery were included. Specimens were taken from the bilateral lower conjunctival sacs using a cotton swab and cultured. The cultures were identified using MALDI-TOP MS andgyrA, gyrB, parC, andparEgene mutations of QRDR were confirmed by DNA extraction from resistant strains ofS. epidermidiswith a micro-dilution method using ciprofloxacin, levofloxacin, and moxifloxacin.ResultsThe culture positive rate was 61.8% (231) for 374 eye samples. Of the 303 total strains cultured,S. epidermidiswas the most common with 33.7% (102). Ten types of gene mutations were observed in the resistantS. epidermidisof 21 strains. One-point mutation was observed mainly ingyrAandparC, and a small number of mutations were observed inparEin the form of a double point mutations. When there were multiple point mutations in bothgyrAandparC, the highest minimum inhibitory concentration was observed.ConclusionsThe quinolone resistance rate ofS. epidermidisincreased in comparison with previous studies, and resistantS. epidermidisshowed mostly QRDR mutations, which were mainly found ingyrAandparC, and showed strong resistance when mutated in both genes.