An ICU Outbreak Due to Two Populations of Carbapenem-Resistant Klebsiella pneumoniae Isolates Belonging to ST11 and ST39 Types, Harbouring Double Carbapenemase Genes

Carbapenem-resistant <i>Klebsiella pneumoniae</i> isolates harbouring double carbapenemases, from patients in a surgical and transplantation ICU, were investigated to better understand the dispersion of the pathogen. Twenty-three carbapenem-resistant <i>K. pneumoniae</i> isolates harbouring at least two different carbapenemases (by immunochromatography screening), were consecutively collected during a seven-month period from patients in a surgical and transplantation ICU. Identification and susceptibility testing were performed using the MALDI-TOF Vitek MS and the Vitek2 system (BioMerieux), respectively. Whole genome sequencing (WGS) was performed in an Illumina NextSeq2000 platform and MLST and resistome analysis of assembled genomes were performed by ResFinder, through the Center for Genomic Epidemiology platform. All isolates were resistant to ertapenem, imipenem, meropenem, and most to meropenem-varbobactam. Seventeen isolates belonged to the ST11 type and were positive for the OXA-48/NDM combination (by immunochromatography and NGS). Four isolates belonged to the ST39 type and were positive for the KPC/NDM combination (by immunochromatography and NGS). Finally, two isolates belonged to the ST258 type. One of them was positive for the OXA-48/KPC/NDM combination (by immunochromatography), but only <i>bla</i>_KPC was detected by WGS, and the second was positive for the OXA-48/KPC combination (by immunochromatography) and confirmed by WGS. This is the first report of an outbreak in Greece due to two simultaneous carbapenem-resistant populations harbouring double carbapenemases: a larger one comprising ST11 isolates harbouring the combination <i>bla</i>_NDM-1/<i>bla</i>_OXA-48, coupled by a smaller one comprising ST39 isolates harbouring the combination <i>bla</i>_KPC-2/<i>bla</i>_NDM-1. The implications of this particular situation regarding public health as well as intra-nosocomial infection prevention and control should be further monitored and studied.