BUT-1: a new member in the chromosomal inducible class C beta-lactamases family from a clinical isolate of Buttiauxella sp.

An atypical Enterobacteriaceae strain with a beta-lactam susceptibility pattern of inducible cephalosporinase was isolated in Tenon Hospital (Paris, France) from a patient's skull wound infection. Identifications by the API-50CHE biochemical system and 16S rRNA gene sequencing concluded that it was a member of the Buttiauxella genus. The bla gene was cloned and sequenced. The deduced translated product was a 383-amino acid protein (BUT-1) with 75-78% identity with the chromosomal AmpC beta-lactamases of Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae and Escherichia coli. The isoelectric point of 9.0 and the kinetic constants of BUT-1 were comparable with results described for other Ambler class C enzymes. bla(BUT-1) and the associated ampR transcriptional regulator gene were divergently transcribed from a common intercistronic region, a genetic organization already described for other inducible class C beta-lactamases. The deduced amino acid sequence of AmpR shared 85% and 81% identity with AmpR from E. cloacae and C. freundii respectively.