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

Abstract

Background Staphylococcus 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). Methods 377 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. Results The 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. Conclusions The 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.

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“…cn/ VFs/) was used for virulence gene annotation, with coverage≥95% and identity≥95% (Gupta et al 2019). Additionally, quinolone resistance determining regions (QRDR) were analyzed by SnapGene Viewer V. 1.5.2 software (Kang et al 2020). Graphpad prism V. 8.0.2 was used for heat map mapping of antimicrobial resistance genes and virulence genes.…”

Antimicrobial resistance in E. Coli of animal origin and discovery of a novel ICE mobile element in Northeast China

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Elucidating Resistance Mechanisms inStaphylococcus epidermidis: A High-Performing MALDI-TOF MS-Based Proteomic Approach for Predictive Modeling

“…The current dataset is limited to 20,000 Da, meaning that instead of detecting the true protein involved in resistance, the models likely detect a different protein or peptide encoded within the same plasmid involved in the same antibiotic resistance mechanism (Lau et al, 2014). For example, previous studies have demonstrated that the primary mutation responsible for ciprofloxacin resistance are mutations in the gyrA and parC genes, which have masses of 100,144 Da and 91,145 Da, respectively (Kang et al, 2020). Such proteins are outside of the detection range and are therefore not considered when building the model, demonstrating that although model performance may not be optimized to detect the main resistance biomarker directly, highly accurate results can still be achieved by detecting other smaller but related proteins.…”