The ACT-1 plasmid-encoded AmpC β-lactamase is inducible: Detection in a complex β-lactamase background

The purpose of this study was to identify the genetic organization and inducibility of bla_ACT-1 in a clinical isolate of Klebsiella pneumoniae possessing at least five different β-lactamases. The genetic organization of the bla_ACT-1lampR region is identical to those of inducible chromosomal ampC genes. RNA analysis using primer extension demonstrated a five-fold increase in bla_ACT-1 transcript production on exposure to cefoxitin. These findings are significant because induction was detected in a complicated β-lactamase background. In addition, this report is the first to describe an inducible plasmid-encoded AmpC β-lactamase of Enterobacter cloacae origin.