Hypervirulent Klebsiella pneumoniae causing bloodstream infections in Hungary

Hypervirulent Klebsiella pneumoniae (hvKP) can cause severe infections even in healthy individuals. Currently, no data are available on the frequency of hvKP-induced bloodstream infections (BSI) in Hungary. Our investigation revealed that of the 157 K. pneumoniae isolated from BSI in 2020-2022 at a university hospital in Hungary, three (2%) carried the hypervirulence-associated rmpA and iutAiucABCD genes. The complete genomes of these three hvKP isolates were sequenced. They were unrelated and belonged to ST5, ST86, and ST6771, a single-locus variant of ST893, i.e., to internationally known hvKP clones. In the K. pneumoniae ST86 and ST6771 isolates, the rmpA/A2, aerobactin, and salmochelin siderophore genes were located on virulence plasmids highly similar to those of K. pneumoniae ST23 and ST86 isolated in Asia, while the K. pneumoniae ST5 isolate harboured rmpA, iroBCDN, and yersiniabactin locus on a chromosomally integrated ICEKp1 element. Comparison of the core genome MLST of the three Hungarian hvKP isolates to genomes belonging to the same ST/CC deposited in the Bigsdb database of the Pasteur Institute revealed that, although no direct epidemiological link could be established, KP48326 K. pneumoniae ST86, isolated in Pécs, clustered with a Greek isolate (ID-48733). The emergence of K. pneumoniae belonging to known hypervirulent clones in Hungary, albeit sporadic, is alarming and underscores the importance of continued whole-genome-based epidemiological surveillance.IMPORTANCEThis study represents the first investigation of the prevalence of hypervirulent K. pneumoniae (hvKP) in bloodstream infections in Hungary, conducted at the University Hospital of Pécs. Our findings emphasize the need to accurately identify hvKP strains, integrating both phenotypic and genotypic screening. Whole genome sequencing revealed genetic diversity among the Hungarian hvKP isolates, confirming the emergence of globally disseminating hvKP clones-ST86, CC893, and ST5-in Hungary. The localization of hypervirulence-related genes on mobile genetic elements, e.g., on virulence plasmids or on ICEKp1 similar to those found in hvKP isolates from different continents, underscores the significant role of horizontal gene transfer in the spread of hvKP. Overall, the study enhances our understanding of hvKP epidemiology and underscores the importance of continued molecular surveillance and control measures to mitigate the threat of hvKP infections in Hungary.