Respiratory illness caused by Corynebacterium diphtheriae and C. ulcerans, and use of diphtheria anti-toxin in the United States, 1996-2018

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.

Corynebacterium ramonii sp. nov., a novel toxigenic member of the Corynebacterium diphtheriae species complex

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.

A case study of environmental pollution by pathogenic bacteria and metal(oid)s at Soran Landfill Site, Erbil, Iraqi Kurdistan Region

Environmental pollution is a serious issue all around the world, especially when it is caused by metal(oid)s and pathogenic microorganisms. This study reports here for the first time on the contamination of soil and water with metal(oid)s and pathogenic bacteria directly resulting from the Soran Landfill Site. Soran landfill is a level 2 solid waste disposal site that lacks leachate collection infrastructure. The site is potentially an environmental and public hazard caused by metal(oid)s content and significantly dangerous pathogenic microorganisms through leachate release into the soil and nearby river. This study reports on the levels of the metal(oid)s content of As, Cd, Co, Cr, Cu, Mn, Mo, Pb, Zn, and Ni obtained by inductively coupled plasma mass spectrometer in soil, leachate stream mud, and leachate samples. Five pollution indices are used to assess potential environmental risks. According to the indices, Cd and Pb contamination is significant, whereas As, Cu, Mn, Mo, and Zn pollution is moderate. A total of 32 isolates of bacteria were defined from soil, leachate stream mud, and liquid leachate samples: 18, 9, and 5, respectively. Moreover, 16 s rRNA analysis suggested that the isolates belong to three enteric bacterial phyla of Proteobacteria, Actinobacteria, and Firmicutes. The closest GenBank matches of 16S rDNA sequences indicated the presence of the genera: Pseudomonas, Bacillus, Lysinibacillus, Exiguobacterium, Trichococcus, Providencia, Enterococcus, Macrococcus, Serratia, Salinicoccus, Proteus, Rhodococcus, Brevibacterium, Shigella, Micrococcus, Morganella, Corynebacterium, Escherichia, and Acinetobacter. The identity percentage was mostly between 95%-100%. The results of this study show the levels of microbiological and geochemical contamination of soils, surface and potentially ground water with harmful microorganisms and toxic metal(oid)s originating specifically from Soran landfill leachate which subsequently incorporated into the surrounding environment, creating thus a considerable health and environmental risk.

Toxigenic Corynebacterium diphtheriae Infection in Cat, Texas, USA

We report a toxigenic strain of Corynebacterium diphtheriae isolated from an oozing dermal wound in a pet cat in Texas, USA. We also describe the epidemiologic public health efforts conducted to identify potential sources of infection and mitigate its spread and the molecular and genetic studies performed to identify the bacterium.

Exotoxin-Targeted Drug Modalities as Antibiotic Alternatives

The paradigm of antivirulence therapy dictates that bacterial pathogens are specifically disarmed but not killed by neutralizing their virulence factors. Clearance of the invading pathogen by the immune system is promoted. As compared to antibiotics, the pathogen-selective antivirulence drugs hold promise to minimize collateral damage to the beneficial microbiome. Also, selective pressure for resistance is expected to be lower because bacterial viability is not directly affected. Antivirulence drugs are being developed for stand-alone prophylactic and therapeutic treatments but also for combinatorial use with antibiotics. This Review focuses on drug modalities that target bacterial exotoxins after the secretion or release-upon-lysis. Exotoxins have a significant and sometimes the primary role as the disease-causing virulence factor, and thereby they are attractive targets for drug development. We describe the key pre-clinical and clinical trial data that have led to the approval of currently used exotoxin-targeted drugs, namely the monoclonal antibodies bezlotoxumab (toxin B/TcdB, Clostridioides difficile), raxibacumab (anthrax toxin, Bacillus anthracis), and obiltoxaximab (anthrax toxin, Bacillus anthracis), but also to challenges with some of the promising leads. We also highlight the recent developments in pre-clinical research sector to develop exotoxin-targeted drug modalities, i.e., monoclonal antibodies, antibody fragments, antibody mimetics, receptor analogs, neutralizing scaffolds, dominant-negative mutants, and small molecules. We describe how these exotoxin-targeted drug modalities work with high-resolution structural knowledge and highlight their advantages and disadvantages as antibiotic alternatives.

Prepatellar Bursitis with Abscess due to Corynebacterium ulcerans

Corynebacteria are ubiquitous and reside as skin and mucosa commensals in animals. They are considered contaminants in clinical specimens, but significant clinical data points to their virulence and pathogenic potential over the last two decades. Corynebacteria can cause both community-acquired and nosocomial infections. Corynebacterium diphtheriae (C. diphtheriae) responsible for diphtheria has declined over the previous two decades with an increase in a similar clinical syndrome by Corynebacterium ulcerans (C. ulcerans) in Europe. As per recent studies, C. ulcerans shares similar virulence factors with C. diphtheriae. C. ulcerans has been implicated in airway infections, skin and soft tissue infections, lymphadenitis, wound infections, and rarely necrotizing fasciitis. Pet or farm animals have been the source of these infections to humans, as per recent reports. Strains can be either toxigenic or nontoxigenic. Due to recent advances, methods to characterize strains have become easier with mass spectrometry. Antimicrobial susceptibility testing is a must for definite treatment as C. ulcerans can be resistant to first-line antibiotic therapy. If resources are available, it is prudent to find if there is any toxin production. Here, we describe a rural farmer in central Missouri presenting with acute-onset right knee pain diagnosed with right prepatellar bursitis with abscess due to C. ulcerans infection. He recovered with surgical debridement and antimicrobial therapy. This is the first case of C. ulcerans causing prepatellar bursitis with an abscess as per medical literature review.