Mutational and Phylogenetic Analysis of <i>nfxB</i> Gene in Multidrug-Resistant Clinical Isolates of <i>Pseudomonas aeruginosa</i> Hyperexpressing MexCD-OprJ Efflux Pump

Abstract

The present study focused on MexCD-OprJ efflux pump and its regulatory gene nfxB in multidrug resistant (MDR) clinical isolates of Pseudomonas aeruginosa collected from Kerala, South India. Semi-quantitative reverse transcription-PCR technique was employed to detect hyperexpression of the efflux pump gene, mexD. Amplicons from nfxB gene of isolates hyperexpressing the efflux pump were sequenced for mutational and phylogenetic analysis. Among 29 isolates of MDR P. aeruginosa, increased mexD transcription was detected in 10.3% of the isolates when compared with P. aeruginosa reference strain, PAO (MTCC-3541). Various synonymous and non-synonymous mutations in nfxB regulatory gene sequences were detected. Notably, mutations detected in the strains designate Pa6 and Pa7 have been found to be novel and are hitherto unreported in GenBank data base. The genetic divergence and homogeneity of the nfxB regulatory gene sequences of mexCD-oprJ operon were clearly apparent in the phylogram generated employing similar sequences retrieved from the public database.

Identification of Efflux Pump Mutations in Pseudomonas aeruginosa from Clinical Samples

“…The MexAB-OprM is the first efflux pump detected in P. aeruginosa , regulated by the mexR gene, and is able to expel a wide range of antibiotics such as β-lactams, fluoroquinolones, tetracycline, macrolides, β-lactamase inhibitors, chloramphenicol, and sulfonamides. The efflux pump MexCD-OprJ, regulated by the nfxB gene is similar to the MexAB-OprM efflux pump [ 11 ]. Other efflux pumps such as MexEF-OprN and MexXY-OprM show resistance to a narrower spectrum of antibiotics [ 12 ].…”