Treatment failures of a carbapenem-colistin regimen among patients with bacteremia due to sequence type 258 (ST258), KPC-2-producing Klebsiella pneumoniae were significantly more likely if both agents were inactive in vitro, as defined by a colistin MIC of >2 μg/ml and the presence of either a major ompK36 porin mutation (guanine and alanine insertions at amino acids 134 and 135 [ins aa 134-135 GD], IS5 promoter insertion [P = 0.007]) or a doripenem MIC of >8 μg/ml (P = 0.01).
The genomic analysis of three isolates (from blood culture, nasal and anal swabs) showed that the bacteremia was caused by a KPC-2 producing extensively drug-resistant K64-ST11 hypermucousviscous <i>K. pneumoniae</i> (hmKP) harboring several virulence and antimicrobial resistance genes.
Central venous catheter, mechanical ventilation, high Pitt bacteraemia score, hospitalization prior to culture, and prior antibiotic use (carbapenem, aminoglycoside and tigecycline) were identified as independent risk factors for carbapenem-non-susceptible K. pneumoniae BSI, which was mostly caused by KPC-2 in northern China.