Open AccessCloning and sequencing of the β‐lactamase gene and surrounding DNA sequences of Citrobacter braakii , Citrobacter murliniae , Citrobacter werkmanii , Escherichia fergusonii and Enterobacter cancerogenus
Author(s) -
Naas Thierry,
Aubert Daniel,
Fortineau Nicolas,
Nordmann Patrice
Publication year - 2002
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2002.tb11374.x
Subject(s) - citrobacter freundii , citrobacter , biology , enterobacter cloacae , escherichia coli , microbiology and biotechnology , plasmid , enterobacter , genetics , gene , enterobacteriaceae
To further identify the origins of plasmid‐mediated cephalosporinases that are currently spreading worldwide, the chromosomal β‐lactamase genes of Citrobacter braakii , Citrobacter murliniae , Citrobacter werkmanii reference strains and of Escherichia fergusonii and Enterobacter cancerogenus clinical isolates were cloned and expressed into Escherichia coli and sequenced. These β‐lactamases had all a single pI value >8 and conferred a typical AmpC‐type resistance pattern in E. coli recombinant strains. The cloned inserts obtained from genomic DNAs of each strain encoded Ambler class C β‐lactamases. The AmpC‐type enzymes of C. murliniae , C. braakii and C. werkmanii shared 99%, 96% and 95% amino acid sequence identity, respectively, with chromosomal AmpC β‐lactamases from Citrobacter freundii . The AmpC‐type enzyme of E. cancerogenus shared 85% amino acid sequence identity with the chromosomal AmpC β‐lactamase of Enterobacter cloacae OUDhyp and the AmpC‐type enzyme of E. fergusonii shared 96% amino acid sequence identity with that of E. coli K12. The ampC genes, except for E. fergusonii , were associated with genes homologous to regulatory ampR genes of other chromosomal class C β‐lactamases that explain inducibility of β‐lactamase expression in these strains. This work provides further evidence of the molecular heterogeneity of class C β‐lactamases.