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. 2024 Sep 3;65(11):38.
doi: 10.1167/iovs.65.11.38.

Relationship Between Fluoroquinolone Resistance and Mutations in the Quinolone Resistance-Determining Region in Corynebacterium macginleyi

Nobuhiro Kato  1 , Masatoshi Haruta  1 , Rikki Arai  1 , Kazunori Sato  1 , Kei Furushima  1 , Kanako Yokomizo  1 , Miki Okuno  2 , Takeshi Yamamoto  2 , Yoshitoshi Ogura  2 , Shigeo Yoshida  1
Affiliations

Relationship Between Fluoroquinolone Resistance and Mutations in the Quinolone Resistance-Determining Region in Corynebacterium macginleyi

Nobuhiro Kato et al. Invest Ophthalmol Vis Sci. .

Abstract

Purpose: The purpose of this study was to investigate the bacterial composition in the conjunctiva and to determine the relationship between fluoroquinolone resistance and mutations in the quinolone resistance-determining region (QRDR) in Corynebacterium macginleyi (C. macginleyi).

Methods: Bacteria isolated from conjunctival swabs of patients awaiting ophthalmic surgery or patients with presumed keratoconjunctivitis were included in this study. For C. macginleyi isolates from 49 samples, the minimum inhibitory concentrations (MICs) of second- to fourth-generation fluoroquinolones were determined by broth microdilution. Additionally, we determined the sequence of the QRDR in the gyrA gene of C. macginleyi-positive isolates by direct sequencing and investigated the relationship between the QRDR mutation and the MICs of fluoroquinolones for C. macginleyi.

Results: Among 423 eyes of 296 preoperative patients who underwent conjunctival culture testing, 105 eyes of 89 patients were culture-positive, and among 148 eyes of 147 patients with keratoconjunctivitis, 55 eyes of 54 patients were culture-positive. C. macginleyi accounted for the largest proportion of cultured organisms (34.8%). C. macginleyi-positive isolates were found in 45 eyes of 37 preoperative patients and in 4 eyes of 4 patients with keratoconjunctivitis. Direct sequencing revealed that 91.8% of C. macginleyi-positive isolates had amino acid mutations in the QRDR and 95.5% of mutations were found at Ser-87 and Asp-91. Isolates harboring double mutations at Ser-87 and Asp-91 were resistant to second- to fourth-generation fluoroquinolones. One isolate with double mutations at Ser-87 and Ala-88 but no mutation in Asp-91 showed intermediate susceptibility to moxifloxacin, a fourth-generation fluoroquinolone.

Conclusions: C. macginleyi isolated from conjunctiva harboring QRDR amino acid mutations were resistant to second- to fourth-generation fluoroquinolones.

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Conflict of interest statement

Disclosure: N. Kato, None; M. Haruta, None; R. Arai, None; K. Sato, None; K. Furushima, None; K. Yokomizo, None; M. Okuno, None; T. Yamamoto, None; Y. Ogura, None; S. Yoshida, None

Figures

Figure 1.
Figure 1.
Comparison of the full-length amino acid sequence of Corynebacterium macginleyi type strain (CP068291.1) with the amino acid sequence of the quinolone resistance-determining region of each isolate. Comparison of amino acid sequence of CP068291.1 and AB359263.1 with those of each isolate. Alignment was performed using Molecular Evolutionary Genetics Analysis software version 11.
Figure 2.
Figure 2.
Representative image of the broth microdilution method for Corynebacterium macginleyi. LC790634 (Ser87 and Asp91) has no amino acid mutation in the QRDR and is sensitive to fluoroquinolones. LC790652 (Ser87Leu and Asp91Gly) has an amino acid mutation in the QRDR and is resistant to fluoroquinolones. Positive control (50 µL of bacterial solution added), and negative control (no bacterial solution added). The final inoculum volume for each well was adjusted to approximately 2.5 × 104 colony forming units/well. The number on each plate indicates the minimum inhibitory concentration for the corresponding drug. Abbreviations: GFLX, gatifloxacin; LFLX, lomefloxacin; LVFX, levofloxacin; MFLX, moxifloxacin; NFLX, norfloxacin; OFLX, ofloxacin; TFLX, tosufloxacin.
See this image and copyright information in PMC

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