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Antimicrobial Agents and Chemotherapy, April 2005, p. 1289-1293, Vol. 49, No. 4
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.4.1289-1293.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Evidence for Multiple-Antibiotic Resistance in Campylobacter jejuni Not Mediated by CmeB or CmeF

Lilian Pumbwe,1 Luke P. Randall,2 Martin J. Woodward,2 and Laura J. V. Piddock1*

Antimicrobial Agents Research Group, Division of Immunity and Infection, University of Birmingham, Birmingham,1 Department of Food and Environmental Safety, Veterinary Laboratory Agency (Weybridge), Addlestone, Surrey, United Kingdom2

Received 23 April 2004/ Returned for modification 14 July 2004/ Accepted 27 November 2004

An efflux system, CmeABC, in Campylobacter jejuni was previously described, and a second efflux system, CmeDEF, has now been identified. The substrates of CmeDEF include ampicillin, ethidium bromide, acridine, sodium dodecyl sulfate (SDS), deoxycholate, triclosan, and cetrimide, but not ciprofloxacin or erythromycin. C. jejuni NCTC11168 and two efflux pump knockout strains, cmeB::Kanr and cmeF::Kanr, were exposed to 0.5 to 1 µg of ciprofloxacin/ml in agar plates. All mutants arising from NCTC11168 were resistant to ciprofloxacin but not to other agents and contained a mutation resulting in the replacement of threonine 86 with isoleucine in the quinolone resistance-determining region of GyrA. Mutants with two distinct phenotypes were selected from the efflux pump knockout strains. Mutants with the first phenotype were resistant to ciprofloxacin only and had the same substitution within GyrA as the NCTC11168-derived mutants. Irrespective of the parent strain, mutants with the second phenotype were resistant to ciprofloxacin, chloramphenicol, tetracycline, ethidium bromide, acridine orange, and SDS and had no mutation in gyrA. These mutants expressed levels of the efflux pump genes cmeB and cmeF and the major outer membrane protein gene porA similar to those expressed by the respective parent strains. No mutations were detected in cmeF or cmeB. Accumulation assays revealed that the mutants accumulated lower concentrations of drug. These data suggest the involvement of a non-CmeB or -CmeF efflux pump or reduced uptake conferring multiple-antibiotic resistance, which can be selected after exposure to a fluoroquinolone.


* Corresponding author. Mailing address: Antimicrobial Agents Research Group, Division of Infection and Immunity, University of Birmingham, Birmingham, B15 2TT, United Kingdom. Phone: (44) 121-414-6966. Fax: (44) 121-414-6815. E-mail: l.j.v.piddock{at}bham.ac.uk.


Antimicrobial Agents and Chemotherapy, April 2005, p. 1289-1293, Vol. 49, No. 4
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.4.1289-1293.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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