Development of a rapid detection system for fluoroquinolone-resistant Corynebacterium macginleyi.

We previously reported an increase in high-level fluoroquinolone-resistant Corynebacterium macginleyi isolates from conjunctival swab specimens and investigated the relationship between fluoroquinolone resistance and mutations in the quinolone resistance-determining region (QRDR) of the gene encoding DNA gyrase subunit A (gyrA). The purpose of this study was to develop a rapid system for detecting fluoroquinolone-resistant C. macginleyi using TaqMan single nucleotide polymorphism (SNP) genotyping assays. The study included 49 strains of C. macginleyi, of which 45 strains were isolated from patients awaiting ophthalmic surgery and 4 strains were from patients with presumed keratoconjunctivitis. Real-time polymerase chain reaction (PCR) and SNP genotyping assays were performed by designing TaqMan probes targeting conserved regions in the gyrA gene of C. macginleyi and QRDR sequences associated with fluoroquinolone resistance. Real-time PCR and SNP genotyping assays were completed in approximately 3 h. Genotyping was successful in all 49 strains, and the QRDR nucleotide sequences of the C. macginleyi isolates were compared with the results of the SNP genotyping assays. The SNP genotyping assays effectively discriminated C. macginleyi from other bacterial species and allowed for the determination of fluoroquinolone resistance acquisition in C. macginleyi. TaqMan SNP genotyping assays may serve as a useful tool for the rapid detection of fluoroquinolone-resistant C. macginleyi in conjunctival swab specimens.