This study determined the types of AmpC enzymes produced by Klebsiella pneumoniae isolates resistant to third-generation cephalosporins and the clonality of these isolates. The presence of AmpC enzymes was identified by cephalosporin–cloxacillin synergy tests. Genes encoding AmpC enzymes were characterised by PCR and sequencing. Pulsed-field gel electrophoresis (PFGE) was used to type the isolates. Fifteen K. pneumoniae isolates were positive for blaAmpC, 13 were positive for blaACC-1 and two were positive for blaDHA-1. Production of the DHA-1 enzyme was inducible. The ampR gene was identified upstream of the blaDHA-1 gene. PFGE demonstrated the polyclonal origin of the isolates carrying blaACC-1.