Expression of the efflux pump genes cmeB, cmeF and the porin gene porA in multiple-antibiotic-resistant Campylobacter jejuni.
OBJECTIVE
In Escherichia coli, increased expression of efflux pumps and/or decreased expression of porins can confer multiple antibiotic resistance (MAR), causing resistance to at least three unrelated classes of antibiotics, detergents and dyes. It was hypothesized that in Campylobacter jejuni, the efflux systems CmeABC, CmeDEF and the major outer membrane porin protein, MOMP (encoded by porA) could confer MAR.


METHODS
The expression of cmeB, cmeF and porA in 32 MAR C. jejuni isolated from humans or poultry was determined by comparative (C)-reverse transcriptase (RT)-PCR and denaturing DHPLC. A further 13 ethidium bromide-resistant isolates and three control strains were also investigated. Accumulation of ciprofloxacin+/-carbonyl cyanide-m-chlorophenyl hydrazone (CCCP) was also determined for all strains.


RESULTS
Although resistance to ethidium bromide has been associated with MAR, expression of all three genes was similar in the ethidium bromide-resistant isolates. These data indicate that CmeB, CmeF and MOMP play no role in resistance to this agent in C. jejuni. Six MAR isolates over-expressed cmeB, 3/32 over-expressed cmeB and cmeF. No isolates over-expressed cmeF alone. Expression of porA was similar in all isolates. All nine isolates that over-expressed cmeB contained a mutation in cmeR, substituting glycine 86 with alanine. All cmeB over-expressing isolates also accumulated low concentrations of ciprofloxacin, which were restored to wild-type levels in the presence of CCCP.


CONCLUSIONS
These data indicate that over-expression of cmeB is associated with MAR in isolates of C. jejuni. However, as cmeB was over-expressed by only one-third (9/32) of MAR isolates, these data also indicate other mechanisms of MAR in C. jejuni.
Pumbwe
Lilian
L
Antimicrobial Agents Research Group, Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
Randall
Luke P
LP
Woodward
Martin J
MJ
Piddock
Laura J V
LJ
D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D016123:Campylobacter jejuni / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D002939:Ciprofloxacin / Q000378:metabolism / Q000494:pharmacology; D003470:Culture Media; D027081:DNA Gyrase / Q000235:genetics; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D018272:Porins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics
D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D003470:Culture Media; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; D026901:Membrane Transport Proteins; D018272:Porins; D015534:Trans-Activators; C095080:major outer membrane protein, Campylobacter jejuni; C070725:SoxS protein, E coli; D002939:Ciprofloxacin; D001618:beta-Lactamases; D027081:DNA Gyrase