Abstract: Background Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathotype that often infects healthy individuals and causes sever infections like organ abscesses. The objective of our study was to examine the epidemiology of hvKp isolates derived from blood cultures (BCI) or showing carbapenem-resistance (CRI) in Germany and to characterise the strains phenotypically and molecularly. Methods BCI and CRI were collected from 11 centres across Germany over a period of 6-12 months. The isolates were phenotypically characterised by string test and by agar dilution with 4 ug/ml tellurite. Furthermore, all isolates were molecularly tested for aerobactin, salmochelin, yersiniabactin, colibactin, and the regulators of capsule production rmpA and rmpA2 with the eazyplex®-hv-K. pneumoniae assay. The genomes of all strains in which the rmpA or rmpA2 gene was detected or which were positive in the string test were sequenced. Results 576 BCI and 75 CRI were included in the study. A high Kleborate score of 3-5 was significantly more common in CRI (17.3%) compared to BCI (7.4%; p=0.008). The rmpA and/or rmpA2 gene was detected in 6.1% (BCI) and in 9.3 % (CRI). RmpA2 but not rmpA showed a trend to be more prevalent in CRI (p=0.067 and p=0.619, respectively). Interestingly, the string test and the rmpA/rmpA2-genes were both positive in 22 BCI, while in 33 isolates (48.5%) only the string test and in 13 isolates (19.1%) only the rmpA/rmpA2-genes were positive, suggesting additional regulators for capsule production. Tellurite resistance was more frequent in isolates with a Kleborate score of 3-5 but its specificity was not high enough to serve as a screening tool. The whole-genome sequenced BCI belonged to 50 different sequence types (ST). The most prevalent ST was 23 accounting for 10,2% of isolates. ST23, reported to be associated with hypervirulence, had a Kleborate score of 4-5 in 93.5% of our BCI. Conclusions Potentially hvKp are found in a considerable number of BCI and even more in CRI. It is important to implement surveillance measures to monitor the further spread of this pathotype.

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