Carbapenem- and/or colistin-resistant Klebsiella pneumoniae in Greece: molecular follow-up survey 2022

The continued circulation of this clade in 2022, was confirmed by the detection of K. pneumoniae ST39 isolates in 13 out of the 15 participating hospitals, even though the total number of isolates were found to be lower in 2022 (n=23) than in the same hospitals in 2019 (n=32). In addition, all the 15 participating hospitals had collected at least one isolate of this clade in 2019 and/or 2022, thereby highlighting that carbapenemase-producing K. pneumoniae ST39 can now be considered endemic in hospitals in Greece.

These findings are not only relevant due to the antimicrobial resistance profile of these isolates, but also as a marker of the rapid spread of a new, emerging antimicrobial resistance threat that has established itself in a hospital system; in this case, Greece. This situation is of further concern as a rapid spread may also occur for other antimicrobial-resistant pathogens (which are not a part of this study) with similar modes of transmission. Furthermore, the current dataset provides evidence that a similar event may have already occurred with K. pneumoniae ST323 carrying bla KPC-2 which was not found in previous surveys in Greece – except for one carbapenem-susceptible isolate found in the European survey of carbapenemase-producing Enterobacteriaceae (EuSCAPE) coordinated by ECDC in 2013 – but was detected in six hospitals in 2022.

Based on the established genomic similarity cut-off, 44 within-hospital transmission events were detected in the 15 participating hospitals in the 2022 follow-up study. This is a high number considering that only up to 14 isolates per
hospital were collected, which further indicates the ongoing transmission of carbapenemase-producing K. pneumoniae in the participating Greek hospitals. These transmission events mainly involved well-known international high-risk K. pneumoniae clones such as ST258/512 and ST11, as well as (based on current knowledge) the more Greece-specific high-risk K. pneumoniae clones, ST39 and ST323. The high number of within-hospital transmission events is likely one of the major causes of the rapid spread of newly emerging K. pneumoniae STs among the participating hospitals. However, the repeated transmission of high-risk K. pneumoniae clones to patients could be prevented with appropriate infection prevention and control measures if sufficient resources are made available.

To conclude, the high number of within-hospital transmission events is the most important finding of this study and needs to be urgently addressed as it constitutes a serious issue of patient safety in Greek hospitals. In addition, routine national molecular surveillance is essential to track emerging antimicrobial resistance threats, as well as to assess the effectiveness of the control efforts in use.