Meiguan Yan1, Orhan Sahin, Jun Lin, Qijing Zhang. 1. Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
Abstract
OBJECTIVES: The objective of this study was to determine the contribution of the CmeABC efflux pump to the emergence of fluoroquinolone (FQ)-resistant mutants in Campylobacter jejuni under various levels of selection pressure. METHODS: The frequency of emergence of ciprofloxacin-resistant mutants was measured in wild-type C. jejuni NCTC 11168 and its isogenic cmeB mutant and cmeR mutant (overexpressing cmeABC) using plates containing various concentrations of ciprofloxacin. Representative ciprofloxacin-resistant mutants were selected for gyrA sequence analysis and MIC determination. Accumulation of ciprofloxacin in Campylobacter cells was measured using spectrofluorometry. RESULTS: Mutation of cmeB drastically reduced the frequency of emergence of FQ-resistant mutants at 10x and 32x the MIC of ciprofloxacin, while the cmeR mutant displayed an approximately 17-fold increase in the frequency of emergence of the mutants at 32x the MIC when compared with the wild-type strain. Various point mutations occurred in gyrA in the FQ-resistant mutants selected at 5x and 10x the MIC, while the Thr-86-->Ile mutation was predominant in the mutants selected at 32x the MIC. The Thr-86-->Ile change conferred a high-level resistance to FQs, but other mutations only conferred an intermediate-level FQ resistance. In contrast, all types of gyrA mutations in the CmeABC-overexpressed background conferred high-level resistance to ciprofloxacin. Overexpression of cmeABC significantly reduced the amount of ciprofloxacin accumulated within bacterial cells. CONCLUSIONS: CmeABC is not only important for maintaining high-level resistance to FQs but also contributes significantly to the emergence of FQ-resistant mutants. Inhibition of this efflux pump may prevent the emergence of clinically relevant FQ-resistant Campylobacter mutants.
OBJECTIVES: The objective of this study was to determine the contribution of the CmeABC efflux pump to the emergence of fluoroquinolone (FQ)-resistant mutants in Campylobacter jejuni under various levels of selection pressure. METHODS: The frequency of emergence of ciprofloxacin-resistant mutants was measured in wild-type C. jejuni NCTC 11168 and its isogenic cmeB mutant and cmeR mutant (overexpressing cmeABC) using plates containing various concentrations of ciprofloxacin. Representative ciprofloxacin-resistant mutants were selected for gyrA sequence analysis and MIC determination. Accumulation of ciprofloxacin in Campylobacter cells was measured using spectrofluorometry. RESULTS: Mutation of cmeB drastically reduced the frequency of emergence of FQ-resistant mutants at 10x and 32x the MIC of ciprofloxacin, while the cmeR mutant displayed an approximately 17-fold increase in the frequency of emergence of the mutants at 32x the MIC when compared with the wild-type strain. Various point mutations occurred in gyrA in the FQ-resistant mutants selected at 5x and 10x the MIC, while the Thr-86-->Ile mutation was predominant in the mutants selected at 32x the MIC. The Thr-86-->Ile change conferred a high-level resistance to FQs, but other mutations only conferred an intermediate-level FQ resistance. In contrast, all types of gyrA mutations in the CmeABC-overexpressed background conferred high-level resistance to ciprofloxacin. Overexpression of cmeABC significantly reduced the amount of ciprofloxacin accumulated within bacterial cells. CONCLUSIONS: CmeABC is not only important for maintaining high-level resistance to FQs but also contributes significantly to the emergence of FQ-resistant mutants. Inhibition of this efflux pump may prevent the emergence of clinically relevant FQ-resistant Campylobacter mutants.
Authors: Ky Van Hoang; Norman J Stern; Arnold M Saxton; Fuzhou Xu; Ximin Zeng; Jun Lin Journal: Appl Environ Microbiol Date: 2011-01-28 Impact factor: 4.792
Authors: Chih-Chia Su; Abhijith Radhakrishnan; Nitin Kumar; Feng Long; Jani Reddy Bolla; Hsiang-Ting Lei; Jared A Delmar; Sylvia V Do; Tsung-Han Chou; Kanagalaghatta R Rajashankar; Qijing Zhang; Edward W Yu Journal: Protein Sci Date: 2014-05-06 Impact factor: 6.725
Authors: Mathew D Routh; Yaramah Zalucki; Chih-Chia Su; Qijing Zhang; William M Shafer; Edward W Yu Journal: Adv Enzymol Relat Areas Mol Biol Date: 2011