Screening of qnrA, qnrB and qnrS genes in quinolonesresistant Escherichia coli

Abstract

Uropathogenic E. coli (UPEC) has emerged as a pathogen with extraordinary abilities to brawl the power of drugs used against them. They are responsible for more than 80% of Urinary tract infections. Overall this problem has been associated with significant morbidity costs and huge economic losses. The main objective of the study is to estimate prevalence and fluoroquinolone resistance against UPEC and screening of plasmid mediated quinolone resistance (PMQR) genes. In the present study 250 samples were collected from patients diagnosed for having UTI from an Islamabad based diagnostic centre. All together 145 out of 250 were identified as UPEC by morpho-cultural, biochemical and molecular techniques. Disk-diffusion susceptibility testing revealed that 85 (58.62%) out of 145 isolates were resistant to more than one, tested antibiotic of fluoroquinolones’ family. In UPEC highest rate of resistance was observed against Levofloxacin (80%), followed by Ofloxacin (71.7%), Ciprofloxacin (61.37%), Sparfloxacin (60.6%) and Norfloxacin (57.2%). These 85 fluoroquinolone resistant isolates were then scrutinized for the presence of PMQR genes (qnrA, qnrB, qnrS) by using gene specific primers. Our results revealed that only 2 (2.35%) samples were found to carry qnrB gene, 3 (3.53%) were found carrying qnrS and while qnrA was detected in none of the samples. Selected 58 samples (including qnr positive) were further processed for the quantitative determination of resistance using minimum inhibitory concentration (MIC) followed by minimum bactericidal concentration (MBC). Ciprofloxacin and Levofloxacin drugs were used for determining their MIC and MBC. A much higher resistance trend was observed in samples processed for MIC and MBC, overall 62.07% (36 out of 58) were found to have MIC values ≥128 µg/ml against Ciprofloxacin. However in Levofloxacin resistant isolates, 13 (22.41%) isolates had MIC values ≥128µg/ml. Similarly considering MBC trend of Ciprofloxacin 41 (70.69%) samples out of 58 showed MBC ≥128 µg/ml and in case of Levofloxacin was like 24 (41.38%) isolates out of 58 showed MBC ≥128 µg/ml. Overall much higher resistance trend was observed against fluoroquinolones, along with the plausible presence of PMQR genes. Both quantitative and qualitative determination of resistance clearly depicts failure of the widely recommended drugs against UTI in our region