Anja Berger (Oberschleißheim / DE), Alexandra Dangel (Oberschleißheim / DE), Katja Bengs (Oberschleißheim / DE), Vyacheslav Melnikov (Oberschleißheim / DE), Ina Tammer (Berlin / DE), Vera Forsbach-Birk (Ravensburg / DE), Ulrike Schuhmacher (Ravensburg / DE), Michael Hogardt (Frankfurt a. M. / DE), Jonas Haller (Frankfurt a. M. / DE), Udo Goetsch (Frankfurt a. M. / DE), Imke Friedrichs (Frankfurt a. M. / DE), Annika Hansel (Hildesheim / DE), Andreas Sing (Oberschleißheim / DE)
Background
Occurrence of nontoxigenic Corynebacterium (C.) diphtheriae wound and bloodstream infections in underprivileged and homeless people is a rising problem in Germany. In the last few years the National Consiliary Laboratory of Diphtheria observed an upsurge of infections due to toxigenic strains among homeless people, alcohol and/or drug abusers in Germany. We aimed to study microbiological data, epidemiological data and molecular epidemiology of diphtheria cases in this setting in order to find potential sources of infections.
Materials & Methods
Strain identification was performed by biochemical differentiation and MALDI-TOF analysis (MALDI Biotyper; Bruker Daltonics, Germany). Susceptibility testing was performed according to EUCAST guidelines. Toxigenicity was verified by real-time PCR, the optimized modified Elek-test and a recently published Lateral Flow Immunoassay. Whole generation sequencing (WGS) was carried out on Illumina systems and data analysis by core genome Multi Locus Sequence Typing (cgMLST).
Results
Twelve patients with wound infections were included, harbouring 11 tox+ C. diphtheriae isolates and 1 tox+ C. ulcerans strain, respectively. In addition, a tox+ C. diphtheriae strain was isolated from a positive blood culture in a septic patient. WGS by the NCLoD suggested 7 affected patients had acquired a toxigenic C. diphtheriae strain belonging to the ongoing European 2022 diphtheria refugee outbreak without having a correspondent migration history. The most probable source of infection in the tox+ C. ulcerans case was the stray dog belonging to the homeless person.
Conclusions
We observed 13 diphtheria cases in the setting of homeless and drug abusing people in Germany in the last three years. Among these cases we identified members of one distinct C. diphtheriae cluster belonging of the ongoing European refugee outbreak. Therefore, we recommend increased awareness among clinicians, microbiologists, and institutions working with homeless people and intensified sample collection from wounds and laboratory diagnostics.