Toxigenic Corynebacterium ulcerans is an emerging zoonosis globally, causing both cutaneous and respiratory diphtheria-like illness. In Queensland, human infection with toxigenic C. ulcerans is rare, with only three cases reported before October 2015. This case series describes five subsequent cases of toxigenic C. ulcerans in Queensland with links to companion animals.
All data were collected as part of routine public health response, and strains were whole genome sequenced for further characterisation. Household contacts were screened, treated with appropriate antibiotics, and received a diphtheria toxoid-containing vaccine if more than five years had elapsed since their last dose.
No epidemiological or genomic links could be established between any of the five patients, including between the two cases notified from the same locality within eight days of each other. The C. ulcerans strains from Cases Two, Four and Five were closely related to the strains isolated from their respective pets by whole genome sequencing. Domestic dogs were identified as the most likely mode of transmission for Cases One and Three; however, this was unable to be laboratory confirmed, since Case One\'s dog was treated with antibiotics before it could be tested, and Case Three\'s dog was euthanised and cremated prior to case notification.
These are the first reported Australian cases of this emerging zoonosis with links to companion animals. These cases demonstrate the likely transmission route between companion animals and humans, with no evidence of human-to-human transmission. The existing requirement in the Queensland Health Public Health Management Guidelines, of restrictions on cases and some contacts while awaiting swab results, is currently under review.

The Eurasian beaver (Castor fiber) has been reintroduced successfully in Germany since the 1990s. Since wildlife is an important source of zoonotic infectious diseases, monitoring of invasive and reintroduced species is crucial with respect to the One Health approach. Three Eurasian beavers were found dead in the German federal states of Bavaria, North Rhine-Westphalia and Baden-Wuerttemberg in 2015, 2021 and 2022, respectively. During post-mortem examinations, Corynebacterium (C.) ulcerans could be isolated from the abscesses of two beavers and from the lungs of one of the animals. Identification of the bacterial isolates at the species level was carried out by spectroscopic analysis using MALDI-TOF MS, FT-IR and biochemical profiles and were verified by molecular analysis based on 16-23S internal transcribed spacer (ITS) region sequencing. Molecular characterization of the C. ulcerans isolates using whole-genome sequencing (WGS) revealed a genome size of about 2.5 Mbp and a GC content of 53.4%. Multilocus sequence typing (MLST) analysis classified all three isolates as the sequence type ST-332. A minimum spanning tree (MST) based on cgMLST allelic profiles, including 1211 core genes of the sequenced C. ulcerans isolates, showed that the beaver-derived isolates clearly group on the branch of C. ulcerans with the closest relationship to each other, in close similarity to an isolate from a dog. Antibiotic susceptibility testing revealed resistance to clindamycin and, in one strain, to erythromycin according to EUCAST, while all isolates were susceptible to the other antimicrobials tested.

The Corynebacterium diphtheriae species complex comprises seven bacterial species, including Corynebacterium ulcerans, a zoonotic pathogen from multiple animal species. In this work, we characterise phenotypically and genotypically isolates belonging to two C. ulcerans lineages. Results from phylogenetic analyses, in silico DNA-DNA hybridization (DDH) and MALDI-TOF spectra differentiate lineage 2 from C. ulcerans lineage 1, which, together with their distinct transmission dynamics (probable human-to-human vs animal-to-human), indicates that lineage 2 is a separate Corynebacterium species, which we propose to name Corynebacterium ramonii. This species is of particular medical interest considering that its human-to-human transmission is likely, and that some C. ramonii isolates carry the diphtheria toxin gene.

Corynebacterium ulcerans is a closely related bacterium to the diphtheria bacterium C. diphtheriae, and some C. ulcerans strains produce toxins that are similar to diphtheria toxin. C. ulcerans is widely distributed in the environment and is considered one of the most harmful pathogens to livestock and wildlife. Infection with C. ulcerans can cause respiratory or nonrespiratory symptoms in patients. Recently, the microorganism has been increasingly recognized as an emerging zoonotic agent of diphtheria-like illness in Japan. To clarify the overall clinical characteristics, treatment-related factors, and outcomes of C. ulcerans infection, we analyzed 34 cases of C. ulcerans that occurred in Japan during 2001-2020. During 2010-2020, the incidence rate of C. ulcerans infection increased markedly, and the overall mortality rate was 5.9%. It is recommended that adults be vaccinated with diphtheria toxoid vaccine to prevent the spread of this infection.

Clinical, epidemiologic, and microbiologic analyses revealed emergence of 26 cases of Corynebacterium diphtheriae species complex infections on Réunion Island, France, during 2015-2020. Isolates were genetically diverse, indicating circulation and local transmission of several diphtheria sublineages. Clinicians should remain aware of the risk for diphtheria and improve diagnostic methods and patient management.

Diphtheria toxin-producing Corynebacterium ulcerans is a zoonotic pathogen that causes human diphtheria-like symptoms. After performing whole-genome analysis of the five isolates from sheltered cats in Osaka, Japan, we compared them with genome sequences of 25 strains of C. ulcerans from a public database. The five isolates from cats harbored 14 genes encoding possible virulence factors in diphtheria-toxin-producing C. ulcerans. These isolates also had diphtheria toxin gene-encoding prophage in their chromosome, although differences were found in other prophages possession. Whole-genome single-nucleotide polymorphism analysis showed that cats\' isolates belonged to ST337 branch, as were strains from Japanese human patients, with 41 or more single-nucleotide polymorphisms variations. High-resolution single-nucleotide polymorphism analysis of C. ulcerans was sufficient to distinguish cats\' isolates clearly as not different by conventional genotyping methods.

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We report the first case of airway obstruction due to toxin-producing Corynebacterium ulcerans, successfully managed with venovenous extracorporeal membrane oxygenation (V-V ECMO). A woman aged 73 years who was living with companion animals was intubated for pneumonia of unknown origin and treated with an empirical antimicrobial agent. Corynebacterium species were detected in the sputum and treated as commensal bacteria. Subsequently, the patient suddenly could not ventilate because of central airway obstruction caused by pseudomembrane formation. Therefore, V-V ECMO was initiated. Additional mass spectrometry identified the Corynebacterium species as C. ulcerans. After treatment with antitoxin, the patient was successfully weaned from V-V ECMO. Hence, in patients in contact with companion animals who present with respiratory failure and pseudomembrane formation, C. ulcerans pneumonia should be suspected and treated with antitoxin. C. ulcerans pneumonia may result in an inability to ventilate due to pseudomembrane formation. Therefore, treatment strategies including V-V ECMO should be considered in such cases.

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Hedgehog diphtheric disease (HDD), an ulcerative skin disease with a high fatality rate, is an emerging threat to European hedgehogs (Erinaceus europaeus). We explored the potential role of a panel of zoonotic pathogens in the presumed multifactorial nature of HDD in 188 hedgehogs from 3 wildlife rescue centres in Belgium. As expected, and with a prevalence of 67% in 57 hedgehogs with skin lesions, characteristic of HDD, the occurrence of Corynebacterium ulcerans was strongly associated with the disease. Remarkably, with a prevalence of 42% in affected animals, infections with Borrelia burgdorferi sensu lato were 3.92 times more likely to be detected in HDD (95% confidence interval: 1.650-9.880; p = .0024). Overall, 40 hedgehogs tested positive for the B. burgdorferi sensu lato complex, including Borrelia afzelii (n = 30), Borrelia bavariensis (n = 7) and Borrelia spielmanii (n = 7). Other widely occurring pathogens included Salmonella (prevalence of 19%, with three pulsed-field gel electrophoresis profiles) and Leptospira sp. (prevalence of 11%, including Leptospira interrogans and Leptospira borgpetersenii), but these were not associated with the occurrence of HDD. These findings show that hedgehogs in Belgium represent a significant reservoir of multiple zoonotic bacteria, of which toxigenic C. ulcerans and B. burgdorferi sensu lato are associated with widespread hedgehog skin pathology and mortality.