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Antimicrobial Agents and Chemotherapy, 02 1996, 307-313, Vol 40, No. 2
JL Burns, CD Wadsworth, JJ Barry and CP Goodall
Antibiotic-resistant Burkholderia (Pseudomonas) cepacia is an important
etiologic agent of nosocomial and cystic fibrosis infections. The primary
resistance mechanism which has been reported is decreased outer membrane
permeability. We previously reported the cloning and characterization of a
chloramphenicol resistance determinant from an isolate of B. cepacia from a
patient with cystic fibrosis that resulted in decreased drug accumulation.
In the present studies we subcloned and sequenced the resistance
determinant and identified gene products related to decreased drug
accumulation. Additional drug resistances encoded by the determinant
include resistances to trimethoprim and ciprofloxacin. Sequence analysis of
a 3.4-kb subcloned fragment identified one complete and one partial open
reading frame which are homologous with two of three components of a
potential antibiotic efflux operon from Pseudomonas aeruginosa
(mexA-mexB-oprM). On the basis of sequence data, outer membrane protein
analysis, protein expression systems, and a lipoprotein labelling assay,
the complete open reading frame encodes an outer membrane lipoprotein which
is homologous with OprM. The partial open reading frame shows homology at
the protein level with the C terminus of the protein product of mexB. DNA
hybridization studies demonstrated homology of an internal mexA probe with
a larger subcloned fragment from B. cepacia. The finding of multiple
antibiotic resistance in B. cepacia as a result of an antibiotic efflux
pump is surprising because it has long been believed that resistance in
this organism is caused by impermeability to antibiotics.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Nucleotide sequence analysis of a gene from Burkholderia (Pseudomonas) cepacia encoding an outer membrane lipoprotein involved in multiple antibiotic resistance
Division of Infectious Disease, Children's Hospital and Medical Center, Seattle, Washington, USA. jburns@u.washington.edu
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