JAC Advance Access published online on May 13, 2003
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkg247
© 2003 by The British Society for Antimicrobial Chemotherapy
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Original article
1 Bristol Centre for Antimicrobial Research and Evaluation,
Department of Pathology and Microbiology,
University of Bristol, School of Medical Sciences, University Walk,
Bristol BS8 1TD, UK
* Corresponding author. E-mail: Matthewb.Avison{at}bris.ac.uk.
Received 18 November 2002
; revised 15 January 2003
; accepted 12 March 2003
Aeromonas hydrophila T429125, a human
clinical isolate, possesses three coordinately inducible
Keywords: Aeromonas, Genetic linkage of the penicillinase gene, amp,
and blrAB, encoding the regulator of
-lactamase
expression in Aeromonas spp
-lactamases
encoded by ampH (class D -lactamase), cepH (class C -lactamase)
and imiH (class B -lactamase).
We report that upstream of ampH there are two genes, blrA and blrB, encoding a
putative two-component regulatory system. PCR studies revealed the
same blrAB-amp gene arrangement in all Aeromonas spp. isolates tested; namely, Aeromonas
veronii bv. sobria, Aeromonas jandaei, Aeromonas mediae, Aeromonas salmonicida and Aeromonas trota. A dominant mutation in the predicted
BlrB kinase domain results in -lactamase
overexpression in A. hydrophila T429125, but in
other -lactamase-overexpressing mutants blrAB remains intact. Relative to the parent strain, A. hydrophila T429125, -lactamase- overexpressing
mutants show a clear hierarchy of increased -lactamase
expression: ImiH > CepH > AmpH. The same hierarchy
is seen following -lactam challenge
of A. hydrophila T429125, and correlates with the
number of blr-tag sequences (TTCAC) found upstream of each -lactamase
gene: ampH (one), cepH (two) and imiH (three).-lactamase,
induction, two-component system, Blr, gene regulation
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