Outbreak with clonally related isolates of Corynebacterium ulcerans in a group of water rats

Zoonotic transmission of diphtheria toxin-producing Corynebacterium ulcerans

BACKGROUND

Diphtheria caused by toxin-producing Corynebacterium ulcerans is a re-emerging human disease that can cause local and systemic sequelae. In Australia, toxigenic diphtheria is a rare notifiable communicable disease, due to high-vaccination coverage. The public health management of cutaneous cases of toxigenic C. ulcerans varies between jurisdictions, as opposed to the more uniform public health response to toxigenic Corynebacterium diphtheriae presenting as respiratory or laryngeal diphtheria.

AIM

To report a case of zoonotically acquired C. ulcerans, review evidence on the zoonotic reservoir and reported transmission events, and examine public health guidelines for the management of human and animal contacts.

METHODS AND RESULTS

In this case report, we detail our case investigation, treatment and public health management, including contact tracing and an approach to animal testing. We successfully identified companion canines as probable sources for the human case, with WGS confirming the link. The zoonotic disease link of C. ulcerans to domestic and agricultural animals is established in the literature; however, the management of animal contacts in human cases is inconsistent with jurisdictional or national guidelines.

CONCLUSIONS

While a rare disease, a consistent approach to public health management is warranted to systematically elucidate the disease source and improve understanding of transmission.

Pastern dermatitis outbreak associated with toxigenic and non-toxigenic Corynebacterium diphtheriae and non-toxigenic Corynebacterium ulcerans at a horse stable in Finland, 2021

AIMS

Corynebacterium diphtheriae and Corynebacterium ulcerans, when producing toxin, are the cause of diphtheria, a potentially life-threatening illness in humans. Horses (Equus ferus caballus) are known to be susceptible to infection that may manifest clinically on rare occasions. In late 2021 and early 2022, specimens from five horses suffering from pastern dermatitis were cultured at the Laboratory of Clinical Microbiology at the Faculty of Veterinary Medicine, University of Helsinki, Finland. C. diphtheriae and/or C. ulcerans were recovered from all of these. This study aimed to (1) analyse the bacterial isolates and (2) describe the outbreak and identify possible sources of the infection and infection routes in the stable.

METHODS AND RESULTS

Susceptibility testing, PCR for the tox gene, and Elek test for toxin production in PCR-positive isolates were performed. Whole genome sequencing was also conducted to achieve high-resolution strain typing. An epidemiological survey was done by means of a semi-structured interview of horses' caretaker, and contact tracing was done among people at the stable. Two tox gene-positive, toxin-producing C. diphtheriae belonged to sequence type (ST) 822. Other C. diphtheriae (n = 2, ST828) and C. ulcerans (n = 2, ST325 and ST838) isolates did not carry the tox gene. The epidemiological investigation explored numerous possible routes of transmission, but the definite source of infection was not identified. All established human contacts tested negative for diphtheriae. All horses recovered after antimicrobial treatment.

CONCLUSIONS

Our study shows that C. diphtheriae and C. ulcerans may readily spread among horses at the same stable and complicate pastern dermatitis infections. These potentially zoonotic bacteria can cause outbreaks even in a country with a very low prevalence. Caretakers should be encouraged to wear gloves and practice good hand hygiene when treating infected skin lesions in horses.

Corynebacterium lipophilum sp. nov., a lipophilic bacterium isolated from clinical breast specimens and emended description of the species Corynebacterium pilbarense

Two isolates (MC-18T and MC-17D), representing the Gram-stain-positive, facultatively anaerobic, irregular rod-shaped, non-motile, and non-spore-forming actinobacteria, were isolated from clinical breast specimens in Guangzhou, China. The growth of the isolates is enhanced by supplementing 1% Tween-80 on Luria Bertani agar. Optimal growth of the isolates was observed at 37 °C, pH 7-8, and with 1% (w/v) NaCl on Columbia blood agar. Pairwise comparison of the 16S rRNA gene sequences revealed that isolates MC-18T and MC-17D shared the highest sequence similarities with Corynebacterium liangguodongii 2184T (96.9%), which were lower than the threshold value for species delineation (98.65%). Phylogenetic dendrograms based on the 16S rRNA gene, rpoB gene, and core genomes indicated that two isolates formed a distinct lineage within the genus Corynebacterium. The estimated dDDH, ANIb, ANIm, and AAI values between strain MC-18T and its closely related strains were below the threshold values generally considered for recognizing a new species. The genome DNA G + C contents of both the isolates MC-18T and MC-17D are 60.6%. The two isolates have virulence-related genes of the VF classes of adhesion and antiphagocytosis, and also contain the antimicrobial resistance genes ErmX, mtrA, rpoB2, and RbpA. The major fatty acids (> 10%) of isolates MC-18T and MC-17D were C16:0, C18:1 ω9c, C18:0 and summed feature 5 (anteiso-C18:0 and/or C18:2 ω6,9c). The main respiratory quinone of strain MC-18T was MK-8(H2), and the polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, three unidentified glycolipids, an unidentified aminolipid, and four unidentified phosphoglycolipids. The two isolates lack mycolic acids in the cell envelope. Based on the above findings, the two isolates are considered to represent a novel species of the genus Corynebacterium, for which the name Corynebacterium lipophilum sp. nov. is proposed, with isolate MC-18T (= NBRC 115144T = CCTCC AB 2020201T) as the type strain. An emended description of the Corynebacterium pilbarense is also provided.

Corynebacterium ulcerans Infections in Eurasian Beavers (Castor fiber)

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.

A scoping review of rodent-borne pathogen presence, exposure, and transmission at zoological institutions

BACKGROUND

Rodents are one of the major taxa most likely to carry zoonotic diseases, harboring more than 85 unique zoonotic pathogens. While the significance of rodents' capacity to carry and transmit disease has been characterized in urban settings, the zoo environment is particularly unique given the overlap of collection, free-living, and feeder rodents as well as non-rodent collection animals, staff, and visitors.

ELIGIBILITY CRITERIA

This scoping review examines reports of rodent-borne pathogen detection or transmission in zoo settings extracted from the literature. Papers were included in the final analysis if there was evidence of presence or exposure to a pathogen in a rodent at a zoological institution.

SOURCES OF EVIDENCE

Publications were included from PubMed, CAB Abstracts and Biological Abstracts searched in August 2019.

CHARTING METHODS

Data extracted from publications on pathogen presence/exposure included publication identifiers, study identifiers, infectious agent identifiers, rodent identifiers, and non-rodent collection animal identifiers. Extraction from papers with evidence of disease transmission included number of rodents involved in transmission, non-rodent collection animal species and numbers, and job title of humans involved, diagnostic tests performed, and clinical outcomes.

RESULTS

Aggregate literature examined included 207 publications presenting evidence of pathogen presence and/or exposure in rodents across 43 countries in over 140 zoological institutions. A total of 143 infectious agent genera were identified, comprising 14 viral genera, 31 bacterial genera, 83 parasitic genera, and 15 fungal genera. Of these infectious agents, over 75 % were potentially zoonotic. The most common disease-causing agent genera identified were Leptospira, Toxoplasma, Salmonella, and Yersinia. Additional screening for evidence of pathogen transmission across species yielded 30 publications, indicating an area for future investigation to better inform surveillance and management priorities in order to reduce exposure, infection, and transmission.

CONCLUSIONS

Analyzing the breadth of rodent species and pathogens identified at zoos highlights the unique opportunity zoos have to be at the forefront of the early detection and identification of novel hosts and geographic ranges of rodent-borne pathogens with high impact on both endangered species and people. The overlap of these populations at zoos exemplifies the importance of considering One Health when prioritizing surveillance and risk mitigation of rodent reservoirs at zoos.

Corynebacterium rouxii, a recently described member of the C. diphtheriae group isolated from three dogs with ulcerative skin lesions

Corynebacterium (C.) diphtheriae is one of the two etiological pathogens for human diphtheria with significant morbidity and mortality. Recently, members of its biovar Belfanti have been described as two novel species, C. belfantii and C. rouxii. The most important virulence factor and also the premise to cause diphtheria is the isolate’s capacity to encode and express the diphtheria toxin (DT). In contrast to C. ulcerans, which represents a potentially zoonotic pathogen, C. diphtheriae (incl. the novel deduced species) has almost exclusively been found to comprise a human pathogen. We here report three rare cases of C. rouxii isolation from dogs suffering from disseminated poly-bacterial exsudative to purulent dermatitis and a traumatic labial defect, respectively. The isolates were identified as C. diphtheriae based on commercial biochemistry and matrix-assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI-TOF MS) analysis. However, recently described specific spectral peaks were highly similar to spectra of C. rouxii, which was confirmed by whole genome sequencing. Further investigations of the dog isolates for the presence of DT by tox gene qPCR revealed negative results. The findings from this study point out that skin infections in companion animals can be colonized by uncommon and so believed human specific pathogens, thereby resembling the clinical signs of cutaneous diphtheria.

Epidemiological analysis of Arcanobacterium phocae isolated from cases of mink dermatitis of a single farm

The present study was designed to identify nine Arcanobacterium phocae strains isolated from cases of mink dermatitis of a single farm in Finland and characterize the strains for epidemiological relationships. All nine strains and previously described A. phocae used for comparative purposes were identified and further characterized phenotypically, by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), by Fourier Transform Infrared Spectroscopy (FT-IR) and genotypically by detection of phocaelysin encoding gene phl with a previously developed loop-mediated isothermal amplification (LAMP) assay and by sequencing 16S rRNA gene and gene phl, the elongation factor tu encoding gene tuf and the β subunit of bacterial RNA polymerase encoding gene rpoB. Genetic relatedness among isolates was determined using whole-genome single nucleotide polymorphism (wgSNP) analysis. The wgSNP results, partly the MALDI-TOF MS and FT-IR analyses and sequencing of the genes, revealed that the nine A. phocae strains recovered from a single farm showed close sequence similarities among each other and differed from previously investigated A. phocae strains isolated from other farms and animals in Finland and from the A. phocae type strain. This indicated a close epidemiological relationship of the A. phocae strains isolated from a single farm and that the nine A. phocae strains of the present study might have developed from a common ancestor.

Tox-positive Corynebacterium ulcerans in hedgehogs, Germany. Emerg Microbes Infect 2019;8:211-217. [PMID: 30866774 PMCID: PMC6455118 DOI: 10.1080/22221751.2018.1562312]

Toxigenic Corynebacterium ulcerans may cause both respiratory and cutaneous diphtheria in humans. As a zoonotic emerging pathogen it has been isolated from a wide variety of animals living in captivity, such as livestock, pet, zoo and research animals and additionally in a large number of different wild animals. Here we report the isolation of tox-positive C. ulcerans in four hedgehogs with cutaneous diphtheria and pneumonia, respectively.

Multilocus Sequencing of Corynebacterium pseudotuberculosis Biotype Ovis Strains

Thirteen Corynebacterium pseudotuberculosis biotype ovis strains isolated from clinical cases of caseous lymphadenitis in Hungary were characterised using multilocus sequencing and their phylogenetic comparison was carried out on the basis of four housekeeping genes (groEL1, infB, dnaK, and leuA). The in silico analysis of the 16 frequently studied housekeeping genes showed that C. pseudotuberculosis strains could be readily distinguished from C. diphtheriae and C. ulcerans strains; however, sequences of the same genes in the two biotypes of the C. pseudotuberculosis were highly similar; the heterogeneity values were low. Genes dnaK, infB, groEL1, and leuA showed marked genetic variation within C. pseudotuberculosis, and strains of the two biotypes of C. pseudotuberculosis could be differentiated. Analysis of the individual genes showed a fairly conservative nature of C. pseudotuberculosis biotype ovis strains. The greatest genetic differentiation was seen in the dnaK and infB genes and concatenations of these two genes were very useful in the genetic separation of the studied strains.

Corynebacterium ulcerans, an emerging human pathogen

While formerly known infections of Corynebacterium ulcerans are rare and mainly associated with contact to infected cattle, C. ulcerans has become an emerging pathogen today. In Western Europe, cases of respiratory diphtheria caused by C. ulcerans have been reported more often than infections by Corynebacterium diphtheria, while systemic infections are also increasingly reported. Little is known about factors that contribute to host colonization and virulence of this zoonotic pathogen. Research in this field has received new impetus by the publication of several C. ulcerans genome sequences in the past years. This review gives a comprehensive overview of the basic knowledge of C. ulcerans, as well as the recent advances made in the analysis of putative virulence factors.

Chemometric analysis of attenuated total reflectance infrared spectra of Proteus mirabilis strains with defined structures of LPS

Proteus spp. strains are some of the most important pathogens associated with complicated urinary tract infections and bacteremia affecting patients with immunodeficiency and long-term urinary catheterization. For epidemiological purposes, various molecular typing methods have been developed for this pathogen. However, these methods are labor intensive and time consuming. We evaluated a new method of differentiation between strains. A collection of Proteus spp. strains was analyzed by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy in the mid-infrared region. ATR FT-IR spectroscopy used in conjunction with a diamond ATR accessory directly produced the biochemical profile of the surface chemistry of bacteria. We conclude that a combination of ATR FT-IR spectroscopy and mathematical modeling provides a fast and reliable alternative for discrimination between Proteus isolates, contributing to epidemiological research.

The killing of macrophages by Corynebacterium ulcerans

Corynebacterium ulcerans is an emerging pathogen transmitted by a zoonotic pathway with a very broad host spectrum to humans. Despite rising numbers of infections and potentially fatal outcomes, data on the molecular basis of pathogenicity are scarce. In this study, the interaction of 2 C. ulcerans isolates - one from an asymptomatic dog, one from a fatal case of human infection - with human macrophages was investigated. C. ulcerans strains were able to survive in macrophages for at least 20 hours. Uptake led to delay of phagolysosome maturation and detrimental effects on the macrophages as deduced from cytotoxicity measurements and FACS analyses. The data presented here indicate a high infectious potential of this emerging pathogen.

Colonization of human epithelial cell lines by Corynebacterium ulcerans from human and animal sources

Corynebacterium ulcerans is an emerging pathogen transmitted by a zoonotic pathway to humans. Despite rising numbers of infections and potentially fatal outcomes, data on the colonization of the human host are lacking up to now. In this study, adhesion of two C. ulcerans isolates to human epithelial cells, invasion of host cells and the function of two putative virulence factors with respect to these processes were investigated. C. ulcerans strains BR-AD22 and 809 were able to adhere to Detroit562 and HeLa cells, and invade these epithelial cell lines with a rate comparable to other pathogens as shown by scanning electron microscopy, fluorescence microscopy and replication assays. Infection led to detrimental effects on the cells as deduced from measurements of transepithelial resistance. Mutant strains of putative virulence factors phospholipase D and DIP0733 homologue CULC22_00609 generated in this study showed no influence on colonization under the experimental conditions tested. The data presented here indicate a high infectious potential of this emerging pathogen.