Abstract
BackgroundStaphylococcus epidermidis is the most common pathogen in postoperative endophthalmitis and causes various infectious eye diseases. However, there is very little information on fluoroquinolone antibiotic resistance to S. epidermidis identified in conjunctival microbe and analysis of related genes. Here, the authors investigated the rate of resistance to fluoroquinolones of Staphylococcus epidermidis isolated 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 and gyrA, gyrB, parC, and parE gene mutations of QRDR were confirmed by DNA extraction from resistant strains of S. epidermidis with 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. epidermidis was the most common with 33.7% (102). Ten types of gene mutations were observed in the resistant S. epidermidis of 21 strains. One-point mutation was observed mainly in gyrA and parC, and a small number of mutations were observed in parE in the form of a double point mutations. When there were multiple point mutations in both gyrA and parC, the highest minimum inhibitory concentration was observed.ConclusionsThe quinolone resistance rate of S. epidermidis increased in comparison with previous studies, and resistant S. epidermidis showed mostly QRDR mutations, which were mainly found in gyrA and parC, and showed strong resistance when mutated in both genes.
Highlights
Staphylococcus epidermidis is the most common pathogen in postoperative endophthalmitis and causes various infectious eye diseases
In this study, we investigated the composition of the normal conjunctival flora and the rate of resistance to the three fluoroquinolones of S. epidermidis, considered to be the most common causative agent of postoperative endophthalmitis, and the gene mutation pattern of the quinolone-resistance determining region (QRDR) of resistant S. epidermidis
As compared with quinolone-resistant S. epidermidis identified in the skin, the results of this study showed a difference in the amino acid types of mutations, but the gyrA and parC
Summary
Staphylococcus epidermidis is the most common pathogen in postoperative endophthalmitis and causes various infectious eye diseases. Most of the isolates cultured from postoperative endophthalmitis come from conjunctival flora [4] With this in mind, it is important to investigate the antibiotic susceptibility of S. epidermidis. Fluoroquinolone, which is frequently used as a topical antibiotic agent in ophthalmology, primarily inhibits DNA gyrase (topoisomerase II) and topoisomerase lV, which are essential enzymes in bacteria [8,9,10]. This kind of antibiotics cover broad spectrum bacteria, including most aerobic gram-negative and gram-positive bacteria, and possess low toxicity and good ocular surface penetration characteristics [11, 12]. No studies on conjunctival normal flora have been reported for about 10 years, since 2009 [5,6,7]
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