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CmeABC functions as a multidrug efflux system in Campylobacter jejuni
Jun Lin1, Linda Overbye Michel, Qijing Zhang
1Food Animal Health Research Program, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio 44691, USA.
Antimicrobial Agents and Chemotherapy
|June 19, 2002
Summary
Campylobacter jejuni possesses a multidrug efflux pump, CmeABC, which confers resistance to antibiotics and other agents. This efflux pump is crucial for the bacterium's intrinsic resistance mechanisms.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Campylobacter jejuni is a significant cause of human gastroenteritis.
- Increasing antibiotic resistance in C. jejuni necessitates understanding its resistance mechanisms.
- Drug efflux pumps are critical for bacterial multidrug resistance, but their role in C. jejuni is not well-defined.
Purpose of the Study:
- To characterize the CmeABC efflux pump system in Campylobacter jejuni.
- To investigate the contribution of CmeABC to multidrug resistance in C. jejuni.
- To determine the distribution and expression of the cmeABC operon in C. jejuni isolates.
Main Methods:
- Genetic characterization of the cmeABC operon and construction of an isogenic mutant.
- Immunoblotting with specific antibodies to detect protein expression.
- Antimicrobial susceptibility testing, heavy metal resistance assays, and bile salt tolerance assays.
- Accumulation assays using ethidium bromide and ciprofloxacin.
- Efflux pump inhibition studies using carbonyl cyanide m-chlorophenylhydrazone.
- PCR analysis for gene distribution.
Main Results:
- The cmeABC operon encodes a tripartite multidrug efflux pump (CmeA, CmeB, CmeC).
- A cmeB mutant (9B6) exhibited significantly reduced resistance (2- to 4,000-fold) to various antimicrobial agents, heavy metals, and bile salts.
- Mutant 9B6 showed increased intracellular accumulation of ethidium bromide and ciprofloxacin compared to wild-type.
- Efflux pump inhibition restored ciprofloxacin accumulation in wild-type to levels seen in the mutant.
- The cmeABC operon is widely distributed and constitutively expressed in C. jejuni isolates.
Conclusions:
- CmeABC functions as a major tripartite multidrug efflux pump in C. jejuni.
- This efflux system contributes significantly to the intrinsic resistance of C. jejuni to a broad spectrum of antimicrobial compounds.
- Understanding the CmeABC efflux pump is vital for developing strategies to combat C. jejuni infections and antibiotic resistance.