Affiliation:
1. Department of Microbiology, University of Copenhagen, Copenhagen, Denmark
Abstract
ABSTRACT
We report here the first gene-encoded resistance mechanism to the swine growth enhancer olaquindox. The genetic elements involved in resistance to olaquindox were subcloned and sequenced from a conjugative plasmid isolated from
Escherichia coli
. The subcloned fragment contained two open reading frames,
oqxA
and
oqxB
, that are homologous to several resistance-nodulation-cell-division family efflux systems from different species. The putative protein sequences were aligned to both experimentally verified and putative efflux pumps. We show that
oqxA
and
oqxB
are expressed in
E. coli
. Plasmids containing the
oqxAB
genes yielded high (>128 μg/ml) resistance to olaquindox in
E. coli
, whereas strains containing the control plasmid showed low resistance to the drug (8 μg/ml). The
oqxAB
-encoded pump also conferred high (>64 μg/ml) resistance to chloramphenicol. We demonstrate that the subcloned fragment conferred H
+
-dependent ethidium efflux abilities to
E. coli
strain N43. In addition, we show that the efflux system is dependent on the host TolC outer membrane protein when expressed in
E. coli
.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology