Rapid fluoroquinolone resistance detection in Pseudomonas aeruginosa using mismatch amplification mutation assay-based real-time PCR

Background. Antimicrobial resistance (AMR) is an ever-increasing global health concern. One crucial facet in tackling the AMR epidemic is earlier and more accurate AMR diagnosis, particularly in the dangerous and highly multi-drug-resistant ESKAPE pathogen, Pseudomonas aeruginosa.Objectives. We aimed to develop two SYBR Green-based mismatch amplification mutation assays (SYBR-MAMAs) targeting GyrA T83I (gyrA248) and GyrA D87N, D87Y and D87H (gyrA259). Together, these variants cause the majority of fluoroquinolone (FQ) AMR in P. aeruginosa.Methods. Following assay validation, the gyrA248 and gyrA259 SYBR-MAMAs were tested on 84 Australian clinical P. aeruginosa isolates, 46 of which demonstrated intermediate/full ciprofloxacin resistance according to antimicrobial susceptibility testing.Results. Our two SYBR-MAMAs correctly predicted an AMR phenotype in the majority (83%) of isolates with intermediate/full FQ resistance. All FQ-sensitive strains were predicted to have a sensitive phenotype. Whole-genome sequencing confirmed 100 % concordance with SYBR-MAMA genotypes.Conclusions. Our GyrA SYBR-MAMAs provide a rapid and cost-effective method for same-day identification of FQ AMR in P. aeruginosa. An additional SYBR-MAMA targeting the GyrB S466Y/S466F variants would increase FQ AMR prediction to 91 %. Clinical implementation of our assays will permit more timely treatment alterations in cases where decreased FQ susceptibility is identified, leading to improved patient outcomes and antimicrobial stewardship.