Mutational analyses of regulatory genes, mexR, nalC, nalD and mexZ of mexAB-oprM and mexXY operons, in efflux pump hyperexpressing multidrug-resistant clinical isolates of Pseudomonas aeruginosa

Mutational analyses of regulatory genes, mexR, nalC, nalD and mexZ of mexAB-oprM and mexXY... The present study deals with membrane-bound efflux pumps, MexAB-OprM and MexXY and their respective regulatory genes mexR, nalC, nalD and mexZ in multidrug resistant (MDR) Pseudomonas aeruginosa. Following antibiotic sensitivity testing and detection of various beta-lactamases, hyperexpression of efflux pump genes, mexB and mexY in the isolates was investigated using semi-quantitative and real-time reverse transcription-PCR. Amplicons from regulatory genes were sequenced and subjected to mutational and phylogenetic analysis. Twenty-nine clinical isolates of P. aeruginosa were obtained from a total of 144 MDR gram-negative bacteria collected from Kerala State, South India. All strains were found to be resistant to ampicillin and nalidixic acid with 13.8, 44.8 and 31% testing positive for extended-spectrum beta-lactamases, metallo-beta-lactamases and AmpC producers respectively. Increased mexB and mexY transcription was detected respectively in 10.3 and 20.7% of the isolates in comparison with P. aeruginosa reference strain, PAO (MTCC). Co-expression of MexY was also observed in MexB overproducers. Various synonymous/and non-synonymous mutations in regulatory gene sequences of efflux pump operons were detected. In the strain designate Pa16, mexR was found to harbour four novel point mutations with one transversion and three transitions which included a substitution of an ochre codon with that for serine. The gene also displayed a novel mutation involving insertion of a cysteine at the 444th base position, followed by an opal codon. The genetic divergence and homogeneity of the concatenated (mexR, nalC and nalD) regulatory gene sequences of mexAB-oprM operon was apparent in the phylogram generated with similar sequences retrieved from public database. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png World Journal of Microbiology and Biotechnology Springer Journals

Mutational analyses of regulatory genes, mexR, nalC, nalD and mexZ of mexAB-oprM and mexXY operons, in efflux pump hyperexpressing multidrug-resistant clinical isolates of Pseudomonas aeruginosa

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Publisher
Springer Netherlands
Copyright
Copyright © 2018 by Springer Science+Business Media B.V., part of Springer Nature
Subject
Life Sciences; Microbiology; Biotechnology; Biochemistry, general; Environmental Engineering/Biotechnology; Applied Microbiology
ISSN
0959-3993
eISSN
1573-0972
D.O.I.
10.1007/s11274-018-2465-0
Publisher site
See Article on Publisher Site

Abstract

The present study deals with membrane-bound efflux pumps, MexAB-OprM and MexXY and their respective regulatory genes mexR, nalC, nalD and mexZ in multidrug resistant (MDR) Pseudomonas aeruginosa. Following antibiotic sensitivity testing and detection of various beta-lactamases, hyperexpression of efflux pump genes, mexB and mexY in the isolates was investigated using semi-quantitative and real-time reverse transcription-PCR. Amplicons from regulatory genes were sequenced and subjected to mutational and phylogenetic analysis. Twenty-nine clinical isolates of P. aeruginosa were obtained from a total of 144 MDR gram-negative bacteria collected from Kerala State, South India. All strains were found to be resistant to ampicillin and nalidixic acid with 13.8, 44.8 and 31% testing positive for extended-spectrum beta-lactamases, metallo-beta-lactamases and AmpC producers respectively. Increased mexB and mexY transcription was detected respectively in 10.3 and 20.7% of the isolates in comparison with P. aeruginosa reference strain, PAO (MTCC). Co-expression of MexY was also observed in MexB overproducers. Various synonymous/and non-synonymous mutations in regulatory gene sequences of efflux pump operons were detected. In the strain designate Pa16, mexR was found to harbour four novel point mutations with one transversion and three transitions which included a substitution of an ochre codon with that for serine. The gene also displayed a novel mutation involving insertion of a cysteine at the 444th base position, followed by an opal codon. The genetic divergence and homogeneity of the concatenated (mexR, nalC and nalD) regulatory gene sequences of mexAB-oprM operon was apparent in the phylogram generated with similar sequences retrieved from public database.

Journal

World Journal of Microbiology and BiotechnologySpringer Journals

Published: May 30, 2018

References

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