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We have provided an existing summary up to a certain point: The study investigates the molecular epidemiology of *Erysipelothrix rhusiopathiae* strains affecting poultry and mammals, focusing on the development of a multilocus sequence typing (MLST) scheme. Analyzing 165 isolates, it revealed high genetic diversity with 72 identified sequence types. Notably, 34.5% clustered into the predominant sequence type (STC9), which includes strains from both avian and mammalian origins, including humans. The congruence of strain clustering from pulsed-field gel electrophoresis (PFGE) with MLST was minimal. Five SpaA protein variants were identified based on strain phylogeny, and the majority of strains (89.7%) harbored a domain with nine C-terminal tandem repeats, while the number of repeats varied between 7 to 13 among isolates. Extensive virulence gene profiling showed that over 90% of isolates carried 16 putative virulence genes, indicating a weakly clonal nature of the species and its limited host specificity. A detailed analysis confirmed no association between SpaA types and host type, suggesting shared reservoirs and pathogenic pathways among diverse hosts. The presence of strains from both poultry and pigs in the same PFGE clusters indicates potential transmission routes between species. Additionally, certain spaA gene variants were distributed independently of host origin, and no specific linkage was established between serotypes and sequence types or PFGE patterns. With evidence of zoonotic potential, these findings underscore the necessity for comprehensive epidemiological studies to better understand the pathogenic mechanisms and virulence factors of *E. rhusiopathiae* strains.
We have the opportunity to refine the existing summary (only if needed) with some more context below.
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The same authors showed that the commercial vaccine Koganei 65–0.15, which lacks this amino acid substitution, was still protective against an experimental infection of pigs with a Met-203 variant.

Thus, it was concluded that the respective protein region might not be that essential for protection against _E.

rhusiopathiae_ infections \[[17]\].

Our analysis was based on a comparison with the Fujisawa serotype 1a strain to allow for a comparison with already published data, that also used this strain as reference \[[17]\].

As we did not have access to one of the vaccine strains (inactivated whole cell bacteria) currently used in the field in Germany for protection of swine against Erysipelas, a comparison of our strain collection with these strains still has to be done.

Moreover, targeted virulence assays including the most prominent sequence types and different _spaA_ variants might provide important insight into the impact of a strain’s genetic background and its potential to cause disease.

In summary, with the development of the MLST scheme a highly reproducible epidemiological tool to study _E.

rhusiopathiae_ strains has been established that allows for long-term global studies to assess the evolutionary history and genetic relatedness of isolates belonging to this bacterial pathogen.

Clinical isolates were found to be highly clonal on the one hand (ST complex 9) but also scattered around the entire population of the selected collection.

Applying this MLST technique clearly unravelled a common evolutionary origin of isolates obtained both from avian and mammalian hosts indicating an interspecies transmission and/or common reservoir and a zoonotic potential.

Combined data of MLST, PFGE and SpaA typing provided a good basis for assessing the clonal diversity and molecular make-up of _E.

rhusiopathiae_.

This might be very advantageous in several aspects, including the (i) selection of epidemiological relevant vaccine candidates (ii) estimation of the pathogenic relevance of single putative virulence genes and isolates in future in vitro and in vivo experiments, and (iii) the assessment of the zoonotic risk of the pathogen.

Acknowledgements
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We would like to give our special thanks to all colleagues from laboratories and national institutions in Germany that provided us with _E.

rhusiopathiae_ strain (AniCon Labor GmbH, Höltinghausen; Chemisches und Veterinäruntersuchungsamt Stuttgart, Dr. Felgenträger und Co. - Öko.-chem.

und Pharma GmbH, Dessau-Roßlau; Friedrich-Loeffler-Institut, Greifswald; Landesbetrieb Hessisches Landeslabor, Giessen; Landeslabor Brandenburg, Frankfurt/Oder; Landesuntersuchungsanstalt für das Gesundheits- und Veterinärwesen Sachsen, Dresden; Landesamt für Verbraucherschutz Sachsen-Anhalt, Halle/Saale; RIPAC-LABOR GmbH, Potsdam; Veterinärinstitut Oldenburg, Oldenburg; Ludwig-Maximilian Universität München, München; Stiftung Tierärztliche Hochschule, Hannover).

This work and MK was funded by the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) – FKZ 2813400307- and supported by the Federal Office for Agriculture and Food (BLE) in the framework of the innovation program.

### Additional files

[Additional file 1:](33K, docx)

**Allele profiles, multilocus sequence types (STs) and Spa types of 165** **_E.

rhusiopathiae_** **isolates determined in this study.

** This table provides all relevant data of the 165 _E.

rhusiopathiae_ isolates typed by multilocus sequence typing in the present study.

The data listed include allele types, sequence types (ST), ST complexes (if any), grouping of SpaA protein sequences based on N-terminal sequences and number of C-terminal repeats of the isolates.

In addition, the year of isolation as well as host origin and country of isolation are provided for each of the isolate.

[Additional file 2:](127K, pdf)**Dendrogram for 165 field isolates from birds and mammals and the type strain of** **_Erysipelothrix rhusiopathiae_** **ATCC 19414** **T** **, based on pulsed-field gel electrophoresis macrorestriction patterns generated by digestion with SmaI restriction endonuclease.

** This table provides PFGE banding patterns of 165 _E.

rhusiopathiae_ isolates with their sequence types (STs), ST complexes (if applicable), and epidemiological background (year, country, and host of isolation).

Abbreviations: A = Austria, CH = Switzerland, DK = Denmark, EST = Republic of Estonia, G = Germany, NA = unknown, S = Sweden, USA = United States of America.

Footnotes
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**Competing interests**

The authors declare that they have no competing interests.

**Authors’ contributions**

TJ, HCP, MV and CE designed the study and experimental approaches.

TJ and MK carried out the molecular genetic studies.

TJ and CE analyzed the data, performed sequence analyses and biostatistics and drafted the manuscript.

TS was involved in sequence analysis and biomathematics.

HCP and MV revised the manuscript critically for important intellectual content.

All authors read and approved the final manuscript.

Contributor Information
-----------------------

Traute Janßen, Email: [ed.robal-capir@nessnajt](mailto:dev@null).

Matthias Voss, Email: [ed.ztl@ssoV](mailto:dev@null).

Michael Kühl, Email: [ed.nilreb-uf@lheuK.leahciM](mailto:dev@null).

Torsten Semmler, Email: [ed.ikr@TrelmmeS](mailto:dev@null).

Hans-Christian Philipp, Email: [moc.miehlegni-regnirheob@ppilihp.naitsirhc-snaH](mailto:dev@null).

Christa Ewers, Email: [ed.nesseig-inu.demtev@srewe.atsirhc](mailto:dev@null).

References
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12\.

European Commission (1999) Council Directive 1999/74/EC of 19 July 1999 laying down minimum standards for the protection of laying hens.

Off J L 203:53–57






















































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Articles from Veterinary Research are provided here courtesy of **BMC**

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