Genetic linkage of the penicillinase gene, amp, and blrAB, encoding the regulator of beta-lactamase expression in Aeromonas spp

J Antimicrob Chemother. 2003 Jun;51(6):1351-8. doi: 10.1093/jac/dkg247. Epub 2003 May 13.

Abstract

Aeromonas hydrophila T429125, a human clinical isolate, possesses three coordinately inducible beta-lactamases encoded by ampH (class D beta-lactamase), cepH (class C beta-lactamase) and imiH (class B beta-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 beta-lactamase overexpression in A. hydrophila T429125, but in other beta-lactamase-overexpressing mutants blrAB remains intact. Relative to the parent strain, A. hydrophila T429125, beta-lactamase- overexpressing mutants show a clear hierarchy of increased beta-lactamase expression: ImiH > CepH > AmpH. The same hierarchy is seen following beta-lactam challenge of A. hydrophila T429125, and correlates with the number of blr-tag sequences (TTCAC) found upstream of each beta-lactamase gene: ampH (one), cepH (two) and imiH (three).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aeromonas / enzymology
  • Aeromonas / genetics*
  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Carrier Proteins / genetics
  • Gene Expression Regulation, Bacterial / genetics*
  • Genetic Linkage / genetics*
  • Humans
  • Molecular Sequence Data
  • Penicillinase / genetics*
  • beta-Lactamases / genetics*

Substances

  • Bacterial Proteins
  • BlrA protein, Aeromonas jandaei
  • Carrier Proteins
  • Penicillinase
  • beta-Lactamases
  • oxacillinase