Historical and contemporary features of infections due to Clostridium novyi

Clostridial Myonecrosis: A Comprehensive Review of Toxin Pathophysiology and Management Strategies

Clostridial myonecrosis, commonly known as gas gangrene (GG), is a rapidly progressing and potentially fatal bacterial infection that primarily affects muscle and soft tissue. In the United States, the incidence of GG is roughly 1000 cases per year, while, in developing countries, the incidence is higher. This condition is most often caused by Clostridium perfringens, a Gram-positive, spore-forming anaerobic bacterium widely distributed in the environment, although other Clostridium species have also been reported to cause GG. The CP genome contains over 200 transport-related genes, including ABC transporters, which facilitate the uptake of sugars, amino acids, nucleotides, and ions from the host environment. There are two main subtypes of GG: traumatic GG, resulting from injuries that introduce Clostridium spores into deep tissue, where anaerobic conditions allow for bacterial growth and toxin production, and spontaneous GG, which is rarer and often occurs in immunocompromised patients. Clostridium species produce various toxins (e.g., alpha, theta, beta) that induce specific downstream signaling changes in cellular pathways, causing apoptosis or severe, fatal immunological conditions. For example, the Clostridium perfringens alpha toxin (CPA) targets the host cell's plasma membrane, hydrolyzing sphingomyelin and phosphatidylcholine, which triggers necrosis and apoptosis. The clinical manifestations of clostridial myonecrosis vary. Some patients experience the sudden onset of severe pain, swelling, and muscle tenderness, with the infection progressing rapidly to widespread tissue necrosis, systemic toxicity, and, if untreated, death. Other patients present with discharge, pain, and features of cellulitis. The diagnosis of GG primarily involves clinical evaluation, imaging studies such as X-rays, computer tomography (CT) scans, and culture. The treatment of GG involves surgical exploration, broad-spectrum antibiotics, antitoxin, and hyperbaric oxygen therapy, which is considered an adjunctive treatment to inhibit anaerobic bacterial growth and enhance the antibiotic efficacy. Early recognition and prompt, comprehensive treatment are critical to improving the outcomes for patients affected by this severe and life-threatening condition.

Approaching toxigenic Clostridia from a One Health perspective

Spore-forming pathogens have a unique capacity to thrive in diverse environments, and with temporal persistence afforded through their ability to sporulate. Their prevalence in diverse ecosystems requires a One Health approach to identify critical reservoirs and outbreak-associated transmission chains, given their capacity to freely move across soils, waterways, foodstuffs and as commensals or infecting pathogens in human and animal populations. Among anaerobic spore-formers, genomic resources for pathogens including C. botulinum, C. difficile, and C. perfringens enable our capacity to identify common and unique factors that support their persistence in diverse reservoirs and capacity to cause disease. Publicly available genomic resources for spore-forming pathogens at NCBI's Pathogen Detection program aid outbreak investigations and longitudinal monitoring in national and international programs in public health and food safety, as well as for local healthcare systems. These tools also enable research to derive new knowledge regarding disease pathogenesis, and to inform strategies in disease prevention and treatment. As global community resources, the continued sharing of strain genomic data and phenotypes further enhances international resources and means to develop impactful applications. We present examples showing use of these resources in surveillance, including capacity to assess linkages among clinical, environmental, and foodborne reservoirs and to further research investigations into factors promoting their persistence and virulence in different settings.

Approaching pathogenic Clostridia from a One Health perspective

Spore-forming pathogens have a unique capacity to thrive in diverse environments, and with temporal persistence afforded through their ability to sporulate. These behaviors require a One Health approach to identify critical reservoirs and outbreak-associated transmission chains, given their capacity to freely move across soils, waterways, foodstuffs, and as commensals or infecting pathogens in human and veterinary populations. Among anaerobic spore-formers, genomic resources for pathogens including C. botulinum, C. difficile, and C. perfringens enable our capacity to identify common and unique factors that support their persistence in diverse reservoirs and capacity to cause disease. Publicly available genomic resources for spore-forming pathogens at NCBI's Pathogen Detection program aid outbreak investigations and longitudinal monitoring in national and international programs in public health and food safety, as well as for local healthcare systems. These tools also enable research to derive new knowledge regarding disease pathogenesis, and to inform strategies in disease prevention and treatment. As global community resources, the continued sharing of strain genomic data and phenotypes further enhances international resources and means to develop impactful applications. We present examples showing use of these resources in surveillance, including capacity to assess linkages among clinical, environmental, and foodborne reservoirs and to further research investigations into factors promoting their persistence and virulence in different settings.

LDLR, LRP1, and Megalin redundantly participate in the uptake of Clostridium novyi alpha-toxin

Clostridium novyi alpha-toxin (Tcnα) is a potent exotoxin that induces severe symptoms including gas gangrene, myositis, necrotic hepatitis, and sepsis. Tcnα binds to sulfated glycosaminoglycans (sGAG) for cell-surface attachment and utilizes low-density lipoprotein receptor (LDLR) for rapid entry. However, it was also shown that Tcnα may use alternative entry receptors other than LDLR. Here, we define that LRP1 and Megalin can also facilitate the cellular entry of Tcnα by employing reconstitutive LDLR family proteins. LDLR, LRP1, and Megalin recognize Tcnα via their ligand-binding domains (also known as LDL receptor type A repeats). Notably, LDLR and LRP1 have contrasting expression levels in many different cells, thus the dominant entry receptor for Tcnα could be cell-type dependent. These findings together increase our knowledge of the Tcnα actions and further help to understand the pathogenesis of C. novyi infection-associated diseases.

Clostridium novyi alpha-toxin (Tcnα) also uses LRP1 and Megalin as cellular entry receptors besides LDLR, and this might be a response to cell-type dependent receptor availability for the exotoxin.

Microbiological Evaluation of Water Used in Dental Units

In modern dentistry, dental units are used for the treatment of patients’ teeth, and they need water to operate. Water circulates in a closed vessel system and finally reaches the mucous membranes of the patient as well as the dentist themselves. Therefore, the microbiological safety of this water should be a priority for physicians. This study aims to identify and determine the microbial count, expressed in CFU/mL, in water samples from various parts of the dental unit that are in direct contact with the patient. Thirty-four dental units located in dentistry rooms were analysed. The dentistry rooms were divided into three categories: surgical, conservative, and periodontal. It was found that in surgical rooms, the bacterial count was 1464.76 CFU/mL, and the most common bacterium was Staphylococcus pasteuri—23.88% of the total bacteria identified. In dentistry rooms where conservative treatments were applied, the average bacterial concentration was 8208.35 CFU/mL, and the most common bacterium was Ralsonia pickettii (26.31%). The periodontal rooms were also dominated by R. pickettii (45.13%), and the average bacterial concentration was 8743.08 CFU/mL. Fungi were also detected. Rhodotorula spp., Alternaria spp., and Candida parapsilosis were found to be the most common bacteria which are potentially harmful. This study indicates the need for effective decontamination of the water that is used in dental units and for constant monitoring of the level of contaminants present in the closed vessel system.

Heterologous Immunity Between SARS-CoV-2 and Pathogenic Bacteria

Heterologous immunity, when the memory T cell response elicited by one pathogen recognizes another pathogen, has been offered as a contributing factor for the high variability in coronavirus disease 2019 (COVID-19) severity outcomes. Here we demonstrate that sensitization with bacterial peptides can induce heterologous immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) derived peptides and that vaccination with the SARS-CoV-2 spike protein can induce heterologous immunity to bacterial peptides. Using in silico prediction methods, we identified 6 bacterial peptides with sequence homology to either the spike protein or non-structural protein 3 (NSP3) of SARS-CoV-2. Notwithstanding the effects of bystander activation, in vitro co-cultures showed that all individuals tested (n=18) developed heterologous immunity to SARS-CoV-2 peptides when sensitized with the identified bacterial peptides. T cell recall responses measured included cytokine production (IFN-γ, TNF, IL-2), activation (CD69) and proliferation (CellTrace). As an extension of the principle of heterologous immunity between bacterial pathogens and COVID-19, we tracked donor responses before and after SARS-CoV-2 vaccination and measured the cross-reactive T cell responses to bacterial peptides with similar sequence homology to the spike protein. We found that SARS-CoV-2 vaccination could induce heterologous immunity to bacterial peptides. These findings provide a mechanism for heterologous T cell immunity between common bacterial pathogens and SARS-CoV-2, which may explain the high variance in COVID-19 outcomes from asymptomatic to severe. We also demonstrate proof-of-concept that SARS-CoV-2 vaccination can induce heterologous immunity to pathogenic bacteria derived peptides.

Clostridial Diseases of Horses: A Review

The clostridial diseases of horses can be divided into three major groups: enteric/enterotoxic, histotoxic, and neurotoxic. The main enteric/enterotoxic diseases include those produced by Clostridium perfringens type C and Clostridioides difficile, both of which are characterized by enterocolitis. The main histotoxic diseases are gas gangrene, Tyzzer disease, and infectious necrotic hepatitis. Gas gangrene is produced by one or more of the following microorganisms: C. perfringens type A, Clostridium septicum, Paeniclostridium sordellii, and Clostridium novyi type A, and it is characterized by necrotizing cellulitis and/or myositis. Tyzzer disease is produced by Clostridium piliforme and is mainly characterized by multifocal necrotizing hepatitis. Infectious necrotic hepatitis is produced by Clostridium novyi type B and is characterized by focal necrotizing hepatitis. The main neurotoxic clostridial diseases are tetanus and botulism, which are produced by Clostridium tetani and Clostridium botulinum, respectively. Tetanus is characterized by spastic paralysis and botulism by flaccid paralysis. Neither disease present with specific gross or microscopic lesions. The pathogenesis of clostridial diseases involves the production of toxins. Confirming a diagnosis of some of the clostridial diseases of horses is sometimes difficult, mainly because some agents can be present in tissues of normal animals. This paper reviews the main clostridial diseases of horses.

Large Clostridial Toxins: Mechanisms and Roles in Disease

Large clostridial toxins (LCTs) are a family of bacterial exotoxins that infiltrate and destroy target cells. Members of the LCT family include Clostridioides difficile toxins TcdA and TcdB, Paeniclostridium sordellii toxins TcsL and TcsH, Clostridium novyi toxin TcnA, and Clostridium perfringens toxin TpeL. Since the 19th century, LCT-secreting bacteria have been isolated from the blood, organs, and wounds of diseased individuals, and LCTs have been implicated as the primary virulence factors in a variety of infections, including C. difficile infection and some cases of wound-associated gas gangrene. Clostridia express and secrete LCTs in response to various physiological signals. LCTs invade host cells by binding specific cell surface receptors, ultimately leading to internalization into acidified vesicles. Acidic pH promotes conformational changes within LCTs, which culminates in translocation of the N-terminal glycosyltransferase and cysteine protease domain across the endosomal membrane and into the cytosol, leading first to cytopathic effects and later to cytotoxic effects. The focus of this review is on the role of LCTs in infection and disease, the mechanism of LCT intoxication, with emphasis on recent structural work and toxin subtyping analysis, and the genomic discovery and characterization of LCT homologues. We provide a comprehensive review of these topics and offer our perspective on emerging questions and future research directions for this enigmatic family of toxins.

O-acetylhomoserine sulfhydrylase from Clostridium novyi. Cloning, expression of the gene and characterization of the enzyme

The gene NT01CX_1210 of pathogenic bacterium Clostridium novyi annotated as encoding O-acetylhomoserine sulfhydrylase was cloned and expressed in Escherichia coli. The gene product having O-acetylhomoserine sulfhydrylase activity was purified to homogeneity. The protein showed molecular mass of approximately 184 kDa for the native form and 46 kDa for the subunit. The enzyme catalyzes the γ-substitution reaction of O-acetylhomoserine with maximum activity at pH 7.5. Analysis of C. novyi genome allowed us to suggest that there is only one way for the synthesis of l-methionine in the bacterium. The data obtained may provide the basis for further study of the role of OAHS in Clostridium bacteria and an ascertainment of its mechanism.

Characterizing Peri-Implant and Sub-Gingival Microbiota through Culturomics. First Isolation of Some Species in the Oral Cavity. A Pilot Study

BACKGROUND

In recent years, culture-independent molecular techniques have been developed to investigate microbiota considered uncultivable. However, the data in the literature suggest that molecular techniques and cultural methods target different spectra of bacteria. The objective of this pilot study was to search for not yet identified oral species in the peri-implant and sub-gingival microbiota in patients without signs of oral pathologies, through the use of the culturomics approach, which has never been used before in dentistry.

METHODS

Four patients were enrolled; from each patient, samples of sub-gingival and peri-implant plaque were taken and analysed by culturomics.

RESULTS

Of 48 isolated species, only 30 had been previously identified by metagenomics in other studies; on the contrary, 12 species had never been associated with the oral cavity before, and 5 of them had never been isolated from clinical specimens.

CONCLUSIONS

By adopting culturomics in dentistry, it could be possible to identify a large amount of fastidious microorganisms that inhabit the oral cavity and to more accurately characterize the microorganisms that lead to periodontitis and peri-implantitis. This evidence could represent an important step forward for the diagnosis and treatment of peri-implantitis, as well as a very useful means for the characterization of new potential aetiologic agents.

Characterization of Clostridium novyi isolated from a sow in a sudden death case in Korea

Background

Multifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly. Clostridium novyi type B was identified and isolated from the sudden death case, and the isolate was characterized by molecular analyses and bioassays in the current study.

Results

C. novyi was isolated from the liver of a sow that died suddenly and was confirmed as C. novyi type B by differential PCR. The C. novyi isolate fermented glucose and maltose and demonstrated lecithinase activity, and the cell-free culture supernatant of the C. novyi isolate exhibited cytotoxicity toward Vero cells, demonstrating that the isolate produces toxins. In addition, whole-genome sequencing of the C. novyi isolate was performed, and the complete sequences of the chromosome (2.29 Mbp) and two plasmids (134 and 68 kbp) were identified for the first time. Based on genome annotation, 7 genes were identified as glycosyltransferases, which are known as alpha toxins; 23 genes were found to be related to sporulation; 12 genes were found to be related to germination; and 20 genes were found to be related to chemotaxis.

Conclusion

C. novyi type B was isolated from a sow in a sudden death case and confirmed by biochemical and molecular characterization. Various virulence-associated genes were identified for the first time based on whole-genome sequencing.

Pathobiology and diagnosis of clostridial hepatitis in animals

Clostridia can cause hepatic damage in domestic livestock, and wild and laboratory animals. Clostridium novyi type B causes infectious necrotic hepatitis (INH) in sheep and less frequently in other species. Spores of C. novyi type B can be present in soil; after ingestion, they reach the liver via portal circulation where they persist in phagocytic cells. Following liver damage, frequently caused by migrating parasites, local anaerobic conditions allow germination of the clostridial spores and production of toxins. C. novyi type B alpha toxin causes necrotizing hepatitis and extensive edema, congestion, and hemorrhage in multiple organs. Clostridium haemolyticum causes bacillary hemoglobinuria (BH) in cattle, sheep, and rarely, horses. Beta toxin is the main virulence factor of C. haemolyticum, causing hepatic necrosis and hemolysis. Clostridium piliforme, the causal agent of Tyzzer disease (TD), is the only gram-negative and obligate intracellular pathogenic clostridia. TD occurs in multiple species, but it is more frequent in foals, lagomorphs, and laboratory animals. The mode of transmission is fecal-oral, with ingestion of spores from a fecal-contaminated environment. In affected animals, C. piliforme proliferates in the intestinal mucosa, resulting in necrosis, and then disseminates to the liver and other organs. Virulence factors for this microorganism have not been identified, to date. Given the peracute or acute nature of clostridial hepatitis in animals, treatment is rarely effective. However, INH and BH can be prevented, and should be controlled by vaccination and control of liver flukes. To date, no vaccine is available to prevent TD.

The C. difficile toxin B membrane translocation machinery is an evolutionarily conserved protein delivery apparatus

Large Clostridial Toxins (LCTs) are a family of six homologous protein toxins that are implicated in severe disease. LCTs infiltrate host cells using a translocation domain (LCT-T) that contains both cell-surface receptor binding sites and a membrane translocation apparatus. Despite much effort, LCT translocation remains poorly understood. Here we report the identification of 1104 LCT-T homologs, with 769 proteins from bacteria outside of clostridia. Sequences are widely distributed in pathogenic and host-associated species, in a variety of contexts and architectures. Consistent with these homologs being functional toxins, we show that a distant LCT-T homolog from Serratia marcescens acts as a pH-dependent translocase to deliver its effector into host cells. Based on evolutionary footprinting of LCT-T homologs, we further define an evolutionarily conserved translocase region that we show is an autonomous translocase capable of delivering heterologous cargo into host cells. Our work uncovers a broad class of translocating toxins and provides insights into LCT translocation.

Large Clostridial toxins infiltrate host cells using a translocation domain (LCT-T). Here, using a genomics-driven approach and functional assays, the authors uncover the presence of distant LCT-T homologs in bacteria outside clostridia and provide evidence for a toxic effector function in the gammaproteobacterium Serratia marcescens.

Hepatic gas gangrene caused by Clostridium novyi

We report the case of a patient with advanced gastric cancer and multiple liver metastases, who presented with bacteremia and hepatic gas gangrene caused by Clostridium novyi (C. novyi). The gas gangrene caused abscesses to form within metastatic lesions. This case highlights the antitumor effects of C. novyi in human.