Temporal evolution of polymyxin B-resistant Klebsiella pneumoniae clones recovered from blood cultures in a teaching hospital during a 7-year period

•An increase (30.6%) of PMB resistance rates was observed among K. pneumoniae isolates recovered from blood cultures.•The PMB-R-KPN isolates were classified as XDR (83.3%), MDR (13.9%), or PDR (2.8%).•The blaKPC-2 gene was detected in 28 of 36 (77.8%) PMB-R-KPN isolates. Most PMB-R-KPN belonged to the ST258 (55.6%), followed by ST437 (27.8%).•A C7/ST258/XDR clone also carrying blaCTX-M-14 and rmtB-1 was introduced in 2014.•Twelve of 36 (33.3%) PMB-R-KPN isolates showed disruption of mgrB.