Plasmid-mediated and inducible cephalosporinase DHA-2 from Klebsiella pneumoniae.

A Klebsiella pneumoniae strain resistant to cefoxitin and oxyimino-cephalosporins was cultured from a child hospitalized in Paris, France, in 1992. This isolate harboured a beta-lactamase gene located on an approximately 200 kb non-self-transferable plasmid. The beta-lactamase identified, DHA-2, shared 99% amino acid identity with the AmpC enzyme of Morganella morganii. DHA-2 was a point-mutant derivative of DHA-1 identified previously in a Salmonella enteritidis isolate. DHA-2 expression was inducible due to an ampR regulatory gene. This is the first report of an inducible and plasmid-located cephalosporinase from K. pneumoniae.