Sven Halbedel (Wernigerode / DE), Sabrina Wamp (Wernigerode / DE), Raskit Lachmann (Berlin / DE), Alexandra Holzer (Berlin / DE), Ariane Pietzka (Graz / AT), Werner Ruppitsch (Wien / AT), Hendrik Wilking (Berlin / DE), Antje Flieger (Wernigerode / DE)
Introduction: Invasive listeriosis is a notifiable foodborne disease caused by the bacterium Listeria monocytogenes and characterized by high fatality rates. Systematic collection of pathogen isolates from listeriosis cases, whole genome sequencing (WGS) and phylogenetic analyses allow recognition and termination of outbreaks after source identification as well as risk profiling of abundant lineages. For surveillance of listeriosis in Germany, clinical L. monocytogenes isolates are collected and their genomes sequenced at the Consultant Laboratory for Listeria located at the RKI (1).
Methods: 1802 clinical L. monocytogenes isolates from Germany collected in 2018-2021 were subjected to WGS for subtyping, cluster recognition and virulome/resistome analyses. Clinical information on the different disease manifestations was used for the calculation of the risk for developing materno-fetal and brain infections for the most abundant phylogenetic sublineages.
Results: The collected isolates covered 62% of all notified cases and belonged to 188 infection clusters, partially reflecting large outbreaks (2-4). 42% of the clusters were protracted, 60% generated cases cross-regionally, including 11 multinational clusters. Strain risk profiling for development of materno-fetal and brain infections allowed discrimination of hypervirulent (ST1) and hypovirulent phylogenetic sublineages (ST8, ST14, ST29 and ST155), confirmed by in vitro infection experiments. In hypovirulent sublineages, naturally occurring loss of function mutations were found in several virulence and house-keeping genes.
Summary: Our work provides a comprehensive insight into the population structure of clinical L. monocytogenes isolates in Germany and the genetic and clinical characteristics of the most abundant sublineages. The assignment of hyper- and hypovirulent lineages might lead to the discovery of relevant virulence factors outside of reference strains.
1 – Halbedel et al. J Clin Microbiol. 2018; 56(6):e00119-18
2 – Halbedel et al. Emerg Infect Dis. 2020; 26(7):1456-1464
3 – Lachmann et al. Clin Microbiol Infect. 2021; 27(7):1035.e1-1035.e5
4 – Halbedel et al. Microbiol Spectr. 2023; 10:e0352022