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. 2025 Aug 21;30(33):2500539. doi: 10.2807/1560-7917.ES.2025.30.33.2500539

Figure 2.

Minimum spanning tree based on core genome multilocus sequence typing analysis of ST-574 C. diphtheriae isolates, 2022–2025 (n = 133), from Germany (n = 125), Poland (n = 1) and Switzerland (n = 7)

Samples are colour-coded based on combined geographic, sub-cluster and date of detection characteristics of respective cases, and these include 99 isolates of newly-arriving migrants and 27 isolates belonging to either of two sub-clusters identified in the current study: sub-cluster 1 is in blue and sub-cluster 2 is in purple (Germany) and pink (Poland).

This figure depicts a minimum spanning tree of 133 Corynebacterium diphtheriae ST-574 isolates collected between 2022 and 2025 in Germany, Switzerland, and Poland. There are 125 isolates notified in Germany, seven isolates notified in Switzerland and one isolate notified in Poland depicted. Each circle on the tree represents one or more isolates, with the circle size increasing with increasing number of isolates. Distances between circles indicate allelic differences based on core genome multilocus sequence typing. Closely related clusters of isolates notified in Germany representing migration-associated cases are visible, with two sub-clusters branching off. Sub-cluster 1 includes cases notified in Germany from 2023 to 2025 whereas sub-cluster 2 includes cases notified in Germany and in Poland in 2024 and 2025.