Role of topoisomerase mutations, plasmid mediated resistance (qnr) and acrAB efflux pump in fluoroquinolone resistant clinical isolates of avian Escherichia coli


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Abstract

Introduction

We investigated the role of topoisomerase mutations, increased level of the multidrug efflux pump AcrAB, and the plasmid-borne genes (qnr) in the fluoroquinolone (FQ) resistant avian Escherichia coli simultaneously.

Material and method

Here, we used four FQs (ciprofloxacin, enrofloxacin, ofloxacin and pefloxacin) and eight clinical isolates of E. coli containing six fluoroquinolone-resistant and two fluoroquinolone- susceptible. PCR and direct sequencing methods were used to detect the role of regulator/ repressor gene (acrR).

Objective

The objective of this study was to determine the relationship of these resistance mechanisms for fluoroquinolone resistance.

Result

The results showed that (i) all four fluoroquinolone- resistant isolates have topoisomerase mutation and plasmid borne genes qnrS and aac(6')-Ib; (ii) three FQ (enrofloxacin, ofloxacin and pefloxacin) resistant isolates harboring qnrS genes; (iii) two FQ (ciprofloxacin and pefloxacin) resistant isolates had topoisomerase mutation and plasmid borne gene qnrS; (iv) all fluoroquinolone susceptible were not harboring qnrS gene and topoisomerase mutation (v) All isolates were negative for qnrA and qnrB.

Conclusion

We found that FQs resistance combination was correlated with synergistically contribution of these resistance mechanisms. Plasmid mediated resistance by qnrS was correlated to pefloxacin resistance but did not correlate to ofloxacin, enrofloxacin and ciprofloxacin. This mechanism might be account for the pefloxacin resistance in avian E. coli.

About the authors

M. Yaqoob

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

L. P. Wang

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
China, Nanjing

J. Memon

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

J. Kashif

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

S. Umar

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

Z. Naseer

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

M. F. Iqbal

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

M. Fiaz

Department of Veterinary Medicine

Email: lucp@njau.edu.cn
Pakistan, Rawalpindi

C. P. Lu

Department of Veterinary Medicine

Author for correspondence.
Email: lucp@njau.edu.cn
China, Nanjing

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