Identification of distinct ciprofloxacin susceptibility in Acinetobacter spp. by detection of the gyrA gene mutation using real-time PCR.

Abstract Ciprofloxacin-resistant (CipR) Acinetobacter spp. was associated with a mutation in quinolone resistance-determining region (QRDR) of gyrA gene from Ser83 to Leu83. A total of 54 Acinetobacter baumannii , 11 A. genospecies 3, and 17 A. genospecies 13TU clinical isolates were determined for ciprofloxacin susceptibility and their QRDR sequenced. Most of A. baumannii were CipR and had a mutated QRDR of gyrA gene, and all A. genospecies 3 and 13TU isolates were ciprofloxacin-susceptible (CipS) and had a wild-type QRDR of gyrA gene. A real-time PCR assay was developed to rapidly differentiate the CipR and CipS Acinetobacter spp. This assay was based on probe hybridization followed by melting temperature ( T m ) analysis to discriminate the QRDR of gyrA gene. All CipR strains had a T m at 47 °C, and most of CipS strains had a higher T m at 51.5 °C. Four CipS A. genospecies 3 isolates with an A base at 264 nt of the gyrA gene had a T m at 49.5 °C. The assay can rapidly and accurately identify the mutated QRDR of gyrA gene in CipR Acinetobacter spp., and potentially increase the rate of the appropriate therapy for Acinetobacter infections.