Molecular screening of quinolone resistance mutations in clinical Acinetobacter baumannii isolates using a mismatch amplification mutation assay PCR

Acinetobacter baumannii is a critical opportunistic pathogen known for its extensive antibiotic resistance. This study was conducted to characterise quinolone-resistant A. baumannii for key genetic markers. From a screening of 450 samples, a total of 32 isolates confirmed as A. baumannii by PCR targeting the bfmR gene. Seven of these isolates were found to be phenotypically resistant to quinolones and were selected for further molecular analysis. A three-primer mismatch amplification mutation assay (MAMA) PCR was employed to detect resistance-conferring mutations in the gyrA (S81L) and parC (S84L) genes. All seven isolates showed phenotypic resistance to ciprofloxacin, gatifloxacin and enrofloxacin. The MAMA-PCR results, validated by Sanger sequencing, indicated that six of the seven isolates harboured mutations in gyrA and five of these also possessed a mutation in parC, correlating with the observed phenotypic resistance. The MAMA-PCR provides a rapid and efficient method for screening genetic markers of resistance, which can be valuable for epidemiological surveillance.