Genetic characteristics of toxigenic Clostridia and toxin gene evolution

Design and evaluation of mRNA encoding recombinant neutralizing antibodies for botulinum neurotoxin type B intoxication prophylaxis

Among all natural and synthetic toxins, botulinum neurotoxins (BoNTs), produced by Clostridium botulinum in an anaerobic environment, are the most toxic polymer proteins. Currently, the most effective modalities for botulism prevention and treatment are vaccination and antitoxin use, respectively. However, these modalities are associated with long response time for active immunization, side effects, and donor limitations. As such, the development of more promising botulism prevention and treatment modalities is warranted. Here, we designed an mRNA encoding B9-hFc - a heavy-chain antibody fused to VHH and human Fc that can neutralize BoNT serotype B (BoNT/B) effectively - and assessed its expression in vitro and in vivo. The results confirmed that our mRNA demonstrates good expression in vitro and in vivo. Moreover, a single mRNA lipid nanoparticle injection effectively prevents BoNT/B intoxication in vivo, with effects comparable to those of protein antibodies. In conclusion, we explored and clarified whether mRNA drugs encoding neutralizing antibodies prevent BoNT/B intoxication. Our results provide an efficient strategy for further research on the prevention and treatment of intoxication by botulinum toxin.

"Active carbon" is more advantageous to the bacterial community in the rice rhizosphere than "stable carbon"

Carbon materials are commonly used for soil carbon sequestration and fertilization, which can also affect crop growth by manipulating the rhizosphere bacterial community. However, the comparison of the differences between active carbon (e.g., organic fertilizers) and stable carbon (e.g., biochar) on rhizosphere microdomains is still unclear. Hence, a trial was implemented to explore the influence of control (CK, no fertilizer; NPK, chemical fertilizer), organic fertilizer (CF-O, organic fertilizer; CF-BO, biochar-based organic fertilizer) and biochar material (CF-B, perishable garbage biochar; CF-PMB, pig manure biochar) on the diversity, composition, and interaction of rice rhizosphere bacterial community through 16 S rRNA gene high-throughput sequencing. Our results demonstrate that organic fertilizer increases bacterial alpha-diversity compared to no-carbon supply treatment to the extend, whereas biochar has the opposite effect. The rhizosphere bacterial community composition showed pronounced variations among the various fertilization treatments. The relative abundance in Firmicutes decreased with organic fertilizer application, whereas that in Chloroflexi and Actinobacteria decreased with biochar application. Bacterial network analysis demonstrate that organic fertilizer enhances the complexity and key taxa of bacterial interactions, while biochar exhibits an opposing trend. The findings of our study indicate that organic fertilizer may contribute to a positive and advantageous impact on bacterial diversity and interaction in rice rhizosphere, whereas the influence of biochar is not as favorable and constructive. This study lays the foundation for elucidating the fate of the rhizosphere bacterial community following different carbon material inputs in the context of sustainable agricultural development.

Strategies for Safe Transurethral Injections of Botulinum Toxin into the Bladder Wall

Introduction: Transurethral injections into the bladder wall with botulinum toxin are an established treatment for refractory overactive bladder or detrusor overactivity. With the current injection technique, an average of approx. 18% and up to 40% of botulinum toxin is injected next to the bladder wall, potentially causing reduced efficacy or non-response. The article aims to evaluate the reasons for incorrect injections and propose strategies for complete delivery of the entire botulinum toxin fluid into the bladder wall. Material and Methods: Unstructured literature search and narrative review of the literature. Results: Incorrect injection of botulinum toxin fluid next to the bladder wall is caused by pushing the injection needle too deep and through the bladder wall. Bladder wall thickness decreases with increasing bladder filling and has a thickness of less than 2 mm beyond 100 mL in healthy individuals. Ultrasound imaging of the bladder wall before botulinum toxin injection can verify bladder wall thickness in individual patients. Patient movements during the injection therapy increase the chance of incorrect placement of the needle tip. Conclusions: Based on the literature search, it is helpful and recommended to (1) perform pretreatment ultrasound imaging of the bladder to estimate bladder wall thickness and to adjust the injection depth accordingly, (2) fill the bladder as low as possible, ideally below 100 mL, (3) use short needles, ideally 2 mm, and (4) provide sufficient anesthesia and pain management to avoid patient movements during the injection therapy.

Overview of Bacterial Protein Toxins from Pathogenic Bacteria: Mode of Action and Insights into Evolution

Bacterial protein toxins are secreted by certain bacteria and are responsible for mild to severe diseases in humans and animals. They are among the most potent molecules known, which are active at very low concentrations. Bacterial protein toxins exhibit a wide diversity based on size, structure, and mode of action. Upon recognition of a cell surface receptor (protein, glycoprotein, and glycolipid), they are active either at the cell surface (signal transduction, membrane damage by pore formation, or hydrolysis of membrane compound(s)) or intracellularly. Various bacterial protein toxins have the ability to enter cells, most often using an endocytosis mechanism, and to deliver the effector domain into the cytosol, where it interacts with an intracellular target(s). According to the nature of the intracellular target(s) and type of modification, various cellular effects are induced (cell death, homeostasis modification, cytoskeleton alteration, blockade of exocytosis, etc.). The various modes of action of bacterial protein toxins are illustrated with representative examples. Insights in toxin evolution are discussed.

Blackleg: A Review of the Agent and Management of the Disease in Brazil

The genus Clostridium is an important group of pathogenic and nonpathogenic Gram-positive anaerobic bacteria with a sporulation capacity and wide distribution in different environments, including the gastrointestinal tracts of healthy and diseased animals and humans. Among the pathogenic species of the genus, Clostridium chauvoei stands out as a histotoxic agent. It causes significant myonecrosis such as blackleg, a disease with high lethality, especially in young cattle, and is responsible for significant livestock losses worldwide. The pathogenicity of the disease is complex and has not yet been fully elucidated. Current hypotheses cover processes from the initial absorption to the transport and deposition of the agent in the affected tissues. The virulence factors of C. chauvoei have been divided into somatic and flagellar antigens and soluble antigens/toxins, which are the main antigens used in vaccines against blackleg in Brazil and worldwide. This review provides important information on the first and current approaches to the agent C. chauvoei and its virulence factors as well as a compilation of data on Brazilian studies related to blackleg.

Pathogenicity and virulence of Clostridium botulinum

Clostridium botulinum, a polyphyletic Gram-positive taxon of bacteria, is classified purely by their ability to produce botulinum neurotoxin (BoNT). BoNT is the primary virulence factor and the causative agent of botulism. A potentially fatal disease, botulism is classically characterized by a symmetrical descending flaccid paralysis, which is left untreated can lead to respiratory failure and death. Botulism cases are classified into three main forms dependent on the nature of intoxication; foodborne, wound and infant. The BoNT, regarded as the most potent biological substance known, is a zinc metalloprotease that specifically cleaves SNARE proteins at neuromuscular junctions, preventing exocytosis of neurotransmitters, leading to muscle paralysis. The BoNT is now used to treat numerous medical conditions caused by overactive or spastic muscles and is extensively used in the cosmetic industry due to its high specificity and the exceedingly small doses needed to exert long-lasting pharmacological effects. Additionally, the ability to form endospores is critical to the pathogenicity of the bacteria. Disease transmission is often facilitated via the metabolically dormant spores that are highly resistant to environment stresses, allowing persistence in the environment in unfavourable conditions. Infant and wound botulism infections are initiated upon germination of the spores into neurotoxin producing vegetative cells, whereas foodborne botulism is attributed to ingestion of preformed BoNT. C. botulinum is a saprophytic bacterium, thought to have evolved its potent neurotoxin to establish a source of nutrients by killing its host.

Evaluation of Aluminium Hydroxide Nanoparticles as an Efficient Adjuvant to Potentiate the Immune Response against Clostridium botulinum Serotypes C and D Toxoid Vaccines

Clostridium botulinum serotypes C and D cause botulism in livestock, a neuroparalytic disease that results in substantial economic losses. Vaccination with aluminium-based toxoid vaccines is widely used to control the spread of botulism. Aluminium-based adjuvants are preferred owing to their apparent stimulation of the immune responses to toxoid vaccines when compared to other adjuvants. The aim of our study was to evaluate aluminium hydroxide nanoparticles as a potential substitute for alhydrogel in the botulism bivalent vaccine. Botulism vaccines were formulated with either alhydrogel or nanoalum and comparative efficacy between the two formulations was conducted by evaluating the immune response in vaccinated guinea pigs. A significant increase in immunological parameters was observed, with the antibody titres higher in the serum of guinea pigs (20 IU/mL of anti-BoNT C/D) injected with nanoalum-containing vaccine than guinea pigs inoculated with the standard alhydrogel-containing vaccine (8.7 IU/mL and 10 IU/mL of anti-BoNT C and anti-BoNT D, respectively). Additionally, the nanoalum-containing vaccine demonstrated potency in a multivalent vaccine (20 IU/mL of anti-BoNT C/D), while the standard alhydrogel-containing vaccine showed a decline in anti-BoNT C (5 IU/mL) antibody titres.

Navigating the Complexities Involving the Identification of Botulinum Neurotoxins (BoNTs) and the Taxonomy of BoNT-Producing Clostridia

Botulinum neurotoxins are a varied group of protein toxins that share similar structures and modes of activity. They include at least seven serotypes and over forty subtypes that are produced by seven different clostridial species. These bacterial species are not limited strictly to BoNT-producers as neuro-toxigenic and non-neuro-toxigenic members have been identified within each species. The nomenclature surrounding these toxins and associated bacteria has been evolving as new isolations and discoveries have arisen, resulting in challenges in diagnostic reporting, epidemiology and food safety studies, and in the application of therapeutic products. An understanding of the intricacies regarding the nomenclature of BoNTs and BoNT-producing clostridia is crucial for communication that allows for accurate reporting of information that is pertinent to each situation.

Identification of MicroRNAs Regulating Clostridium perfringens Type C Infection in the Spleen of Diarrheic Piglets

Clostridium perfringens (C. perfringens) type C is one of the common bacteria in piglet diarrhea, which seriously affects the swine industry's development. The spleen plays crucial roles in the resistance and elimination of pathogenic microorganisms, and miRNAs play important roles in regulating piglet diarrhea caused by pathogens. However, the mechanism by which miRNAs in the spleen are involved in regulating C. perfringens type C causing diarrhea in piglets remains unclear. The expression profiles of the spleen miRNAs of 7-day-old piglets challenged by C. perfringens type C were studied using small RNA-sequencing in control (SC), susceptible (SS), and resistant (SR) groups. Eight-eight differentially expressed miRNAs were screened. The KEGG pathway analysis of target genes revealed that the miRNAs were involved in the MAPK, p53, and ECM-receptor interaction signaling pathways. NFATC4 was determined to be a direct target of miR-532-3p and miR-133b using a dual-luciferase reporter assay. Thus, miR-133b and miR-532-3p targeted to NFATC4 were likely involved to piglet resistance to C. perfringens type C. This paper provides the valuable resources to deeply understand the genetic basis of C. perfringens type C resistance in piglets and a solid foundation to identify novel markers of C. perfringens type C resistance.

Molecular Diversity of BoNT-Producing Clostridia—A Still-Emerging and Challenging Problem

The diversity of BoNT-producing Clostridia is still a worrying problem for specialists who explore the evolutionary and taxonomic diversity of C. botulinum. It is also a problem for epidemiologists and laboratory staff conducting investigations into foodborne botulism in humans and animals, because their genetic and phenotypic heterogeneity cause complications in choosing the proper analytical tools and in reliably interpreting results. Botulinum neurotoxins (BoNTs) are produced by several bacterial groups that meet all the criteria of distinct species. Despite this, the historical designation of C. botulinum as the one species that produces botulinum toxins is still exploited. New genetic tools such as whole-genome sequencing (WGS) indicate horizontal gene transfer and the occurrence of botulinum gene clusters that are not limited only to Clostridium spp., but also to Gram-negative aerobic species. The literature data regarding the mentioned heterogeneity of BoNT-producing Clostridia indicate the requirement to reclassify C. botulinum species and other microorganisms able to produce BoNTs or possessing botulinum-like gene clusters. The aim of this study was to present the problem of the diversity of BoNT-producing Clostridia over time and new trends toward obtaining a reliable classification of these microorganisms, based on a complex review of the literature.

Intraoperative abobotulinumtoxinA alleviates pain after surgery and improves general wellness in a translational animal model

Pain after surgery remains a significant healthcare challenge. Here, abobotulinumtoxinA (aboBoNT-A, DYSPORT) was assessed in a post-surgical pain model in pigs. Full-skin-muscle incision and retraction surgery on the lower back was followed by intradermal injections of either aboBoNT-A (100, 200, or 400 U/pig), vehicle (saline), or wound infiltration of extended-release bupivacaine. We assessed mechanical sensitivity, distress behaviors, latency to approach the investigator, and wound inflammation/healing for 5-6 days post-surgery. We followed with immunohistochemical analyses of total and cleaved synaptosomal-associated protein 25 kD (SNAP25), glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor protein-1(Iba1), calcitonin gene-related peptide (CGRP) and substance P (SP) in the skin, dorsal root ganglia (DRG) and the spinal cord of 400 U aboBoNT-A- and saline-treated animals. At Day 1, partial reversal of mechanical allodynia in aboBoNT-A groups was followed by a full reversal from Day 3. Reduced distress and normalized approaching responses were observed with aboBoNT-A from 6 h post-surgery. Bupivacaine reversed mechanical allodynia for 24 h after surgery but did not affect distress or approaching responses. In aboBoNT-A-treated animals cleaved SNAP25 was absent in the skin and DRG, but present in the ipsilateral dorsal horn of the spinal cord. In aboBoNT-A- versus saline-treated animals there were significant reductions in GFAP and Iba1 in the spinal cord, but no changes in CGRP and SP. Analgesic efficacy of aboBoNT-A appears to be mediated by its activity on spinal neurons, microglia and astrocytes. Clinical investigation to support the use of aboBoNT-A as an analgesic drug for post-surgical pain, is warranted.

Comparative Genomics Provides Insights Into Genetic Diversity of Clostridium tyrobutyricum and Potential Implications for Late Blowing Defects in Cheese

Clostridium tyrobutyricum has been recognized as the main cause of late blowing defects (LBD) in cheese leading to considerable economic losses for the dairy industry. Although differences in spoilage ability among strains of this species have been acknowledged, potential links to the genetic diversity and functional traits remain unknown. In the present study, we aimed to investigate and characterize genomic variation, pan-genomic diversity and key traits of C. tyrobutyricum by comparing the genomes of 28 strains. A comparative genomics analysis revealed an “open” pangenome comprising 9,748 genes and a core genome of 1,179 genes shared by all test strains. Among those core genes, the majority of genes encode proteins related to translation, ribosomal structure and biogenesis, energy production and conversion, and amino acid metabolism. A large part of the accessory genome is composed of sets of unique, strain-specific genes ranging from about 5 to more than 980 genes. Furthermore, functional analysis revealed several strain-specific genes related to replication, recombination and repair, cell wall, membrane and envelope biogenesis, and defense mechanisms that might facilitate survival under stressful environmental conditions. Phylogenomic analysis divided strains into two clades: clade I contained human, mud, and silage isolates, whereas clade II comprised cheese and milk isolates. Notably, these two groups of isolates showed differences in certain hypothetical proteins, transcriptional regulators and ABC transporters involved in resistance to oxidative stress. To the best of our knowledge, this is the first study to provide comparative genomics of C. tyrobutyricum strains related to LBD. Importantly, the findings presented in this study highlight the broad genetic diversity of C. tyrobutyricum, which might help us understand the diversity in spoilage potential of C. tyrobutyricum in cheese and provide some clues for further exploring the gene modules responsible for the spoilage ability of this species.

Regulatory Networks Controlling Neurotoxin Synthesis in Clostridium botulinum and Clostridium tetani

Clostridium botulinum and Clostridium tetani are Gram-positive, spore-forming, and anaerobic bacteria that produce the most potent neurotoxins, botulinum toxin (BoNT) and tetanus toxin (TeNT), responsible for flaccid and spastic paralysis, respectively. The main habitat of these toxigenic bacteria is the environment (soil, sediments, cadavers, decayed plants, intestinal content of healthy carrier animals). C. botulinum can grow and produce BoNT in food, leading to food-borne botulism, and in some circumstances, C. botulinum can colonize the intestinal tract and induce infant botulism or adult intestinal toxemia botulism. More rarely, C. botulinum colonizes wounds, whereas tetanus is always a result of wound contamination by C. tetani. The synthesis of neurotoxins is strictly regulated by complex regulatory networks. The highest levels of neurotoxins are produced at the end of the exponential growth and in the early stationary growth phase. Both microorganisms, except C. botulinum E, share an alternative sigma factor, BotR and TetR, respectively, the genes of which are located upstream of the neurotoxin genes. These factors are essential for neurotoxin gene expression. C. botulinum and C. tetani share also a two-component system (TCS) that negatively regulates neurotoxin synthesis, but each microorganism uses additional distinct sets of TCSs. Neurotoxin synthesis is interlocked with the general metabolism, and CodY, a master regulator of metabolism in Gram-positive bacteria, is involved in both clostridial species. The environmental and nutritional factors controlling neurotoxin synthesis are still poorly understood. The transition from amino acid to peptide metabolism seems to be an important factor. Moreover, a small non-coding RNA in C. tetani, and quorum-sensing systems in C. botulinum and possibly in C. tetani, also control toxin synthesis. However, both species use also distinct regulatory pathways; this reflects the adaptation of C. botulinum and C. tetani to different ecological niches.

Analysis of the complete genome sequences of Clostridium perfringens strains harbouring the binary enterotoxin BEC gene and comparative genomics of pCP13-like family plasmids

Background

BEC-producing Clostridium perfringens is a causative agent of foodborne gastroenteritis. It was first reported in 2014, and since then, several isolates have been identified in Japan and the United Kingdom. The novel binary ADP-ribosylating toxin BEC, which consists of two components (BECa and BECb), is encoded on a plasmid that is similar to pCP13 and harbours a conjugation locus, called Pcp, encoding homologous proteins of the type 4 secretion system. Despite the high in vitro conjugation frequency of pCP13, its dissemination and that of related plasmids, including bec-harbouring plasmids, in the natural environment have not been characterised. This lack of knowledge has limited our understanding of the genomic epidemiology of bec-harbouring C. perfringens strains.

Results

In this study, we determined the complete genome sequences of five bec-harbouring C. perfringens strains isolated from 2009 to 2019. Each isolate contains a ~ 3.36 Mbp chromosome and 1–3 plasmids of either the pCW3-like family, pCP13-like family, or an unknown family, and the bec-encoding region in all five isolates was located on a ~ 54 kbp pCP13-like plasmid. Phylogenetic and SNP analyses of these complete genome sequences and the 211 assembled C. perfringens genomes in GenBank showed that although these bec-harbouring strains were split into two phylogenetic clades, the sequences of the bec-encoding plasmids were nearly identical (>99.81%), with a significantly smaller SNP accumulation rate than that of their chromosomes. Given that the Pcp locus is conserved in these pCP13-like plasmids, we propose a mechanism in which the plasmids were disseminated by horizontal gene transfer. Data mining showed that strains carrying pCP13-like family plasmids were unexpectedly common (58/216 strains) and widely disseminated among the various C. perfringens clades. Although these plasmids possess a conserved Pcp locus, their ‘accessory regions’ can accommodate a wide variety of genes, including virulence-associated genes, such as becA/becB and cbp2. These results suggest that this family of plasmids can integrate various foreign genes and is transmissible among C. perfringens strains.

Conclusion

This study demonstrates the potential significance of pCP13-like plasmids, including bec-encoding plasmids, for the characterisation and monitoring of the dissemination of pathogenic C. perfringens strains.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08453-4.

Toxigenic Profile of Clostridium perfringens Strains Isolated from Natural Ingredient Laboratory Animal Diets

Clostridium perfringens is an anaerobic, gram-positive, spore-forming bacterium that ubiquitously inhabits a wide varietyof natural environments including the gastrointestinal tract of humans and animals. C. perfringens is an opportunistic enteropathogen capable of producing at least 20 different toxins in various combinations. Strains of C. perfringens are currentlycategorized into 7 toxinotypes (A, B, C, D, E, F, and G) based on the presence or absence of 6 typing-toxins (α, β, epsilon, iota, enterotoxin, and netB). Each toxinotype is associated with specific histotoxic and enteric diseases. Spontaneous enteritis due to C. perfringens has been reported in laboratory animals; however, the source of the bacteria was unknown. The Quality Assurance Laboratory (QAL) at the National Institute of Environmental Health Sciences (NIEHS) routinely screens incoming animal feeds for aerobic, enteric pathogens, such as Salmonella spp. and E. coli. Recently, QAL incorporated anaerobic screening of incoming animal feeds. To date, the lab has isolated numerous Clostridium species, including C. perfringens, from 23 lots ofnatural ingredient laboratory animal diets. Published reports of C. perfringens isolation from laboratory animal feeds couldnot be found in the literature. Therefore, we performed a toxin profile screen of our isolated strains of C. perfringens usingPCR to determine which toxinotypes were present in the laboratory animal diets. Our results showed that most C. perfringens strains we isolated from the laboratory animal feed were toxinotype A with most strains also possessing the theta toxin. Two of the C. perfringens strains also possessed the β toxin. Our results demonstrated the presence of C. perfringens in nonsterile, natural ingredient feeds for laboratory animals which could serve as a source of this opportunistic pathogen.

Recombinant Escherichia coli Cell Lysates as a Low-Cost Alternative for Vaccines Against Veterinary Clostridial Diseases

This chapter describes a practical, industry-friendly, and efficient vaccine protocol based on the use of Escherichia coli cell fractions (inclusion bodies or cell lysate supernatant) containing the recombinant antigen. This approach was characterized and evaluated in laboratory and farm animals by the seroneutralization assay in mice, thereby showing to be an excellent alternative to induce a protective immune response against clostridial diseases.

Prevalence and Antimicrobial Resistance of Paeniclostridium sordellii in Hospital Settings

(1) Background: The purpose of this study was to determine the prevalence of clostridia strains in a hospital environment in Algeria and to evaluate their antimicrobial susceptibility to antibiotics and biocides. (2) Methods: Five hundred surface samples were collected from surfaces in the intensive care unit and surgical wards in the University Hospital of Tlemcen, Algeria. Bacterial identification was carried out using MALDI-TOF-MS, and then the minimum inhibitory concentrations (MICs) of various antimicrobial agents were determined by the E-test method. P. sordellii toxins were searched by enzymatic and PCR assays. Seven products intended for daily disinfection in the hospitals were tested against Clostridium spp. spore collections. (3) Results: Among 100 isolates, 90 P. sordellii were identified, and all strains were devoid of lethal and hemorrhagic toxin genes. Beta-lactam, linezolid, vancomycin, tigecycline, rifampicin, and chloramphenicol all proved effective against isolated strains. Among all strains tested, the spores of P. sordellii exhibited remarkable resistance to the tested biocides compared to other Clostridium species. The (chlorine-based 0.6%, 30 min), (glutaraldehyde solution 2.5%, 30 min), and (hydrogen peroxide/peracetic acid 3%, 15 min) products achieved the required reduction in spores. (4) Conclusions: Our hospital’s current cleaning and disinfection methods need to be optimized to effectively remove spores from caregivers’ hands, equipment, and surfaces.

Extensive Genome Exploration of Clostridium botulinum Group III Field Strains

In animals, botulism is commonly sustained by botulinum neurotoxin C, D or their mosaic variants, which are produced by anaerobic bacteria included in Clostridium botulinum group III. In this study, a WGS has been applied to a large collection of C. botulinum group III field strains in order to expand the knowledge on these BoNT-producing Clostridia and to evaluate the potentiality of this method for epidemiological investigations. Sixty field strains were submitted to WGS, and the results were analyzed with respect to epidemiological information and compared to published sequences. The strains were isolated from biological or environmental samples collected in animal botulism outbreaks which occurred in Italy from 2007 to 2016. The new sequenced strains belonged to subspecific groups, some of which were already defined, while others were newly characterized, peculiar to Italian strains and contained genomic features not yet observed. This included, in particular, two new flicC types (VI and VII) and new plasmids which widen the known plasmidome of the species. The extensive genome exploration shown in this study improves the C. botulinum and related species classification scheme, enriching it with new strains of rare genotypes and permitting the highest grade of discrimination among strains for forensic and epidemiological applications.

A Sarcina bacterium linked to lethal disease in sanctuary chimpanzees in Sierra Leone

Human and animal infections with bacteria of the genus Sarcina (family Clostridiaceae) are associated with gastric dilation and emphysematous gastritis. However, the potential roles of sarcinae as commensals or pathogens remain unclear. Here, we investigate a lethal disease of unknown etiology that affects sanctuary chimpanzees (Pan troglodytes verus) in Sierra Leone. The disease, which we have named "epizootic neurologic and gastroenteric syndrome" (ENGS), is characterized by neurologic and gastrointestinal signs and results in death of the animals, even after medical treatment. Using a case-control study design, we show that ENGS is strongly associated with Sarcina infection. The microorganism is distinct from Sarcina ventriculi and other known members of its genus, based on bacterial morphology and growth characteristics. Whole-genome sequencing confirms this distinction and reveals the presence of genetic features that may account for the unusual virulence of the bacterium. Therefore, we propose that this organism be considered the representative of a new species, named "Candidatus Sarcina troglodytae". Our results suggest that a heretofore unrecognized complex of related sarcinae likely exists, some of which may be highly virulent. However, the potential role of "Ca. S. troglodytae" in the etiology of ENGS, alone or in combination with other factors, remains a topic for future research.

Analysis of a plasmid encoding botulinum neurotoxin type G gene in Clostridium argentinense

Clostridium argentinense produces botulinum neurotoxin type G (BoNT/G). We sequenced and analyzed the plasmid harboring the bont/G gene, designated pCAG, in C. argentinense strain 2740. The pCAG consisted of 140,070 bp containing the bont/G gene cluster. Although this gene cluster showed high similarities in its DNA sequence and ORF arrangement to those of other bont gene clusters, the other regions of the plasmid did not. A phylogenetic study suggested that pCAG had a unique evolutionary history compared with other clostridial bont-harboring plasmids. This suggests that pCAG is possibly a novel type of plasmid expressing the bont/G gene in C. argentinense.

TRI Genotyping and Chemotyping: A Balance of Power

Fusarium is among the top 10 most economically important plant pathogens in the world. Trichothecenes are the principal mycotoxins produced as secondary metabolites by select species of Fusarium and cause acute and chronic toxicity in animals and humans upon exposure either through consumption and/or contact. There are over 100 trichothecene metabolites and they can occur in a wide range of commodities that form food and feed products. This review discusses strategies to mitigate the risk of mycotoxin production and exposure by examining the Fusarium-trichothecene model. Fundamental to mitigation of risk is knowing the identity of the pathogen. As such, a comparison of current, recommended molecular approaches for sequence-based identification of Fusaria is presented, followed by an analysis of the rationale and methods of trichothecene (TRI) genotyping and chemotyping. This type of information confirms the source and nature of risk. While both are powerful tools for informing regulatory decisions, an assessment of the causes of incongruence between TRI genotyping and chemotyping data must be made. Reconciliation of this discordance will map the way forward in terms of optimization of molecular approaches, which includes data validation and sharing in the form of accessible repositories of genomic data and browsers for querying such data.

Application of botulinum toxin in maxillofacial field: part I. Bruxism and square jaw

The application of botulinum in oral and maxillofacial surgery begins in 1982, where Jan Carruthers started using it for reducing the muscle mass and smoothing the skin, and since then it has been used for cosmetic purposes. In Korea, it is already being used by various specialties including dentistry (oral and maxillofacial surgery, oral medicine), plastic surgery, dermatology, ophthalmology, general surgery, and orthopedic surgery, etc. Each specialty approaches to Botox with its own medical indications. In this article, we will discuss the maxillofacial application of botulinum toxin, which includes theoretical and practical aspects of such as bruxism and square jaw.

How Management Practices Within a Poultry House During Successive Flock Rotations Change the Structure of the Soil Microbiome

The microbiome within a poultry production house influences the attainment of physiologically strong birds and thus food safety and public health. Yet little is known about the microbial communities within the house and the effects on the soil microbes onto which the houses are placed; nor the effects of management practices on their equilibrium. This study looked at the soil bacterial microbiome before a broiler house was constructed, then through 11 flock rotations (2.5 years) that included a partial clean-out and a total clean-out within the management regimen. Major shifts were observed, occurring at the taxonomic class level, related to the introduction of bedding and birds on top of the soil. The partial clean-out of litter did not change the soil bacterial community in any substantial way, only prompting a temporary increase in some genera; however, the total litter clean-out caused a major increase in a cohort of Actinobacteria. The underlying soil contained bacteria beneficial for poultry metabolism, such as Lactobacillus, Faecalibacterium, Bacteriodes, and Ruminococcus. Additionally, management practices affected the class structure of the soil bacterial community beneath the poultry house. The scheduling of these practices should be leveraged to exploit maintenance of beneficial bacteria that maximize microbiome contributions to bird production processes, while minimizing possible antibiotic-resistant bacteria and environmental effects.

Analyses of miRNA in the ileum of diarrheic piglets caused by Clostridium perfringens type C

Clostridium perfringens (C. perfringens) type C is one of major pathogenic causing diarrhea and other intestinal inflammatory diseases in piglets, which seriously affects the healthy development of the swine industries. Studies have found that miRNAs play important roles in regulating piglet diarrhea challenged by pathogenic E. coli and Salmonella. However, little is known miRNAs in the ileum of diarrheic piglets caused by C. perfringens type C. Therefore, we studied the expression profiles of the ileum miRNAs of 7-day-old piglets infected with C. perfringens type C using small RNA-Seq, including control (IC), susceptible (IS) and resistant (IR) groups. As a result, 53 differentially expressed miRNAs were found. KEGG pathway analysis for target genes revealed that these miRNAs were involved in ErbB signaling pathway, MAPK signaling pathway, Jak-STAT signaling pathway and Wnt signaling pathway. The expression correlation analysis between miRNAs and target genes revealed that the expression of miR-7134-5p had negative correlation with target NFATC4, miR-500 had negative correlation with target ELK1, HSPA2 and IL7R, and miR-92b-3p had negative correlation with target CLCF1 in ileum of IR vs IS group, suggesting that miR-7134-5p targeting to NFATC4, miR-500 targeting to ELK1, HSPA2 and IL7R, and miR-92b-3p targeting to CLCF1 were probably involved in piglet resisting C. perfringens type C. The results will provide value resources for better understanding of the genetic basis of C. perfringens type C resistance in piglet and lays a new foundation for identifying novel markers of C. perfringens type C resistance.

The population structure of Clostridium tetani deduced from its pan-genome

Clostridium tetani produces a potent neurotoxin, the tetanus neurotoxin (TeNT) that is responsible for the worldwide neurological disease tetanus, but which can be efficiently prevented by vaccination with tetanus toxoid. Until now only one type of TeNT has been characterized and very little information exists about the heterogeneity among C. tetani strains. We report here the genome sequences of 26 C. tetani strains, isolated between 1949 and 2017 and obtained from different locations. Genome analyses revealed that the C. tetani population is distributed in two phylogenetic clades, a major and a minor one, with no evidence for clade separation based on geographical origin or time of isolation. The chromosome of C. tetani is highly conserved; in contrast, the TeNT-encoding plasmid shows substantial heterogeneity. TeNT itself is highly conserved among all strains; the most relevant difference is an insertion of four amino acids in the C-terminal receptor-binding domain in four strains that might impact on receptor-binding properties. Other putative virulence factors, including tetanolysin and collagenase, are encoded in all genomes. This study highlights the population structure of C. tetani and suggests that tetanus-causing strains did not undergo extensive evolutionary diversification, as judged from the high conservation of its main virulence factors.

Perfringolysin O-Induced Plasma Membrane Pores Trigger Actomyosin Remodeling and Endoplasmic Reticulum Redistribution

Clostridium perfringens produces an arsenal of toxins that act together to cause severe infections in humans and livestock animals. Perfringolysin O (PFO) is a cholesterol-dependent pore-forming toxin encoded in the chromosome of virtually all C. perfringens strains and acts in synergy with other toxins to determine the outcome of the infection. However, its individual contribution to the disease is poorly understood. Here, we intoxicated human epithelial and endothelial cells with purified PFO to evaluate the host cytoskeletal responses to PFO-induced damage. We found that, at sub-lytic concentrations, PFO induces a profound reorganization of the actomyosin cytoskeleton culminating into the assembly of well-defined cortical actomyosin structures at sites of plasma membrane (PM) remodeling. The assembly of such structures occurs concomitantly with the loss of the PM integrity and requires pore-formation, calcium influx, and myosin II activity. The recovery from the PM damage occurs simultaneously with the disassembly of cortical structures. PFO also targets the endoplasmic reticulum (ER) by inducing its disruption and vacuolation. ER-enriched vacuoles were detected at the cell cortex within the PFO-induced actomyosin structures. These cellular events suggest the targeting of the endothelium integrity at early stages of C. perfringens infection, in which secreted PFO is at sub-lytic concentrations.

Effect of Clostridium perfringens type C on TLR4/MyD88/NF-κB signaling pathway in piglet small intestines

Clostridium perfringens (C. perfringens), a Gram-positive bacterium, is one of the main causing piglet diarrhea, which leads serious economic loss in the world swine industries. Generally, the innate immune response plays a critical role in host defense against pathogen invasion. TLR4, a member of the TLR (Toll-like receptor) family, has been considered to implicate in the host immune responses and induce secretion of inflammatory cytokines during bacterial infection. However, little is clear about the effects of TLR4 and key signaling genes in the process of piglet inflammatory and immune responses after C. perfringens infection. This study aims to explore the effect of C. perfringens type C infection on the key mRNAs of TLR4/MyD88/NF-κB signaling pathways during the process of piglet diarrhea. In this study, the expressions of TLR4 and other key mRNAs in the TLR4/MyD88/NF-κB signaling pathways were quantified in piglet ileum and jejunum tissues among IR (intestinal resistance), IS (intestinal susceptibility) and IC (intestinal control) groups by qPCR and Western blot methods, the concentrations of pro-inflammatory cytokines in intestinal tissues and serum immunoglobulins were also tested by ELISA kits. Results showed that compared to IC group, expressions of ileum TLR4 and TNF-α was significantly increased in the IS and IR groups, specially TBK1 gene; the expressions of ileum TLR2, TRAF6, MyD88 and IL-8 mRNAs was significantly up-regulated in the IS group, the expressions of TLR9, NF-κB, IL-6, IFN-γ and MAPK1 genes were not significant differences among the IR, IS and IC groups. Meanwhile, the protein levels of TLR4, HMGB1 and NF-κB were higher in the IS and IR groups. The levels of jejunum IFN-γ and IL-6, ileum IL-6 and IL-12 were risen in the IR group. Serum immunoglobulin IgA and IgG in the IR and IS groups reached a peak on the 72 h and 48 h post infection, respectively. These findings suggest that C. perfringens type C infection induces host immune responses involving in the TLR4/MyD88/NF-κB signaling pathways in ileum than in jejunum, which may provide valuable information for innate immune mechanisms involved in regulation of piglet diarrhea caused by C. perfringens type C infection.

Identification and Characterization of Escherichia coli, Salmonella Spp., Clostridium perfringens, and C. difficile Isolates from Reptiles in Brazil

Considering the increasing popularity of reptiles as pets and their possible role as reservoirs of pathogenic microorganisms, the aim of this study was to isolate Escherichia coli, Salmonella spp., Clostridium perfringens, and C. difficile strains from reptiles in Brazil and to characterize the isolated strains. The characterization was based on phylogenetic typing of E. coli, identification of virulence genes of E. coli, C. perfringens, and C. difficile, serotyping of Salmonella spp., ribotyping and MLST of C. difficile and antimicrobial susceptibility test of pathogenic strains. Cloacal swabs were collected from 76 reptiles, of which 15 were lizards, 16 chelonians, and 45 snakes, either living in captivity, in the wild, or as companion animals. E. coli was isolated from 52 (68.4%) reptiles, of which 46 (88.4%) were characterized as phylogroup B1. The virulence factor CNF1 of E. coli was found in seven (9.2%) sampled animals, whereas the gene of EAST1 was found in isolates from two (2.6%) reptiles. Three isolates positive for CNF1 were resistant to cephalothin, one of which was also resistant to ciprofloxacin, trimethoprim/sulfamethoxazole, and chloramphenicol, being then classified as multidrug resistant strain (MDR). Salmonella enterica was identified in 26 (34.2%) reptiles, of which 13 belonged to the subspecies enterica. Serotypes such as S. Mbandaka, S. Panama, S. Infantis, S. Heidelberg, and S. Anatum were identified. One isolate of S. enterica subsp. houtenae was resistant to cephalothin and ciprofloxacin. C. perfringens type A was isolated from six (7.8%) animals. C. difficile was isolated from three (3.9%) reptiles. Two of these isolates were toxigenic and classified into ribotypes/MLST 081/ST9 and 106/ST42, which have been previously reported to infect humans. In conclusion, reptiles in Brazil can harbor toxigenic C. difficile and potentially pathogenic E. coli and Salmonella enterica subsp. enterica, thus representing a risk to human and animal health.

Immunogenicity of a Bivalent Non-Purified Recombinant Vaccine against Botulism in Cattle

Botulism is a potentially fatal intoxication caused by botulinum neurotoxins (BoNTs) produced mainly by Clostridium botulinum. Vaccination against BoNT serotypes C and D is the main procedure to control cattle botulism. Current vaccines contain formaldehyde-inactivated native BoNTs, which have a time-consuming production process and pose safety risks. The development of non-toxic recombinant vaccines has helped to overcome these limitations. This study aims to evaluate the humoral immune response generated by cattle immunized with non-purified recombinant fragments of BoNTs C and D. Cattle were vaccinated in a two-dose scheme with 100, 200 and 400 µg of each antigen, with serum sampling on days 0, 56, 120, and 180 after vaccination. Animals who received either 200 or 400 μg of both antigens induced titers higher than the minimum required by the Brazilian ministry of Agriculture, Livestock and Food Supply and achieved 100% (8/8) seroconversion rate. Animals vaccinated with commercial toxoid vaccine had only a 75% (6/8) seroconversion rate for both toxins. Animals that received doses containing 400 µg of recombinant protein were the only ones to maintain titers above the required level up until day 120 post-vaccination, and to achieve 100% (8/8) seroconversion for both toxins. In conclusion, 400 µg the recombinant Escherichia coli cell lysates supernatant was demonstrated to be an affordable means of producing an effective and safe botulism vaccine for cattle.

Clostridium sordellii Pathogenicity Locus Plasmid pCS1-1 Encodes a Novel Clostridial Conjugation Locus

A major virulence factor in Clostridium sordellii-mediated infection is the toxin TcsL, which is encoded within a region of the genome called the pathogenicity locus (PaLoc). C. sordellii isolates carry the PaLoc on the pCS1 family of plasmids, of which there are four characterized members. Here, we determined the potential mobility of pCS1 plasmids and characterized a fifth unique pCS1 member. Using a derivative of the pCS1-1 plasmid from strain ATCC 9714 which had been marked with the ermB erythromycin resistance gene, conjugative transfer into a recipient C. sordellii isolate, R28058, was demonstrated. Bioinformatic analysis of pCS1-1 identified a novel conjugation gene cluster defined as the C. sordellii transfer (cst) locus. Interruption of genes within the cst locus resulted in loss of pCS1-1 transfer, which was restored upon complementation in trans. These studies provided clear evidence that genes within the cst locus are essential for the conjugative transfer of pCS1-1. The cst locus is present on all pCS1 subtypes, and homologous loci were identified on toxin-encoding plasmids from Clostridium perfringens and Clostridium botulinum and also carried within genomes of Clostridium difficile isolates, indicating that it is a widespread clostridial conjugation locus. The results of this study have broad implications for the dissemination of toxin genes and, potentially, antibiotic resistance genes among members of a diverse range of clostridial pathogens, providing these microorganisms with a survival advantage within the infected host.

C. sordellii is a bacterial pathogen that causes severe infections in humans and animals, with high mortality rates. While the pathogenesis of C. sordellii infections is not well understood, it is known that the toxin TcsL is an important virulence factor. Here, we have shown the ability of a plasmid carrying the tcsL gene to undergo conjugative transfer between distantly related strains of C. sordellii, which has far-reaching implications for the ability of C. sordellii to acquire the capacity to cause disease. Plasmids that carry tcsL encode a previously uncharacterized conjugation locus, and individual genes within this locus were shown to be required for conjugative transfer. Furthermore, homologues on toxin plasmids from other clostridial species were identified, indicating that this region represents a novel clostridial conjugation locus. The results of this study have broad implications for the dissemination of virulence genes among members of a diverse range of clostridial pathogens.

A Clostridioides difficile bacteriophage genome encodes functional binary toxin-associated genes

Pathogenic clostridia typically produce toxins as virulence factors which cause severe diseases in both humans and animals. Whereas many clostridia like e.g., Clostridium perfringens, Clostridium botulinum or Clostridium tetani were shown to contain toxin-encoding plasmids, only toxin genes located on the chromosome were detected in Clostridioides difficile so far. In this study, we determined, annotated, and analyzed the complete genome of the bacteriophage phiSemix9P1 using single-molecule real-time sequencing technology (SMRT). To our knowledge, this represents the first C. difficile-associated bacteriophage genome that carries a complete functional binary toxin locus in its genome.

Isolation of botulinolysin, a thiol-activated hemolysin, from serotype D Clostridium botulinum: A species-specific gene duplication in Clostridia

Botulinolysin (BLY) is a toxin produced by Clostridium botulinum that belongs to a group of thiol-activated hemolysins. In this study, a protein exhibiting hemolytic activity was purified from the culture supernatant of C. botulinum serotype D strain 4947. The purified protein displayed a single band by sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular mass of 55kDa, and its N-terminal and internal amino acid sequences exhibited high similarity to a group of thiol-activated hemolysins produced by gram-positive bacteria. Thus, the purified protein was identified as the BLY. Using the nucleotide sequences of previously cloned genes for hemolysins, two types of genes encoding BLY-like proteins were cloned unexpectedly. Molecular modeling analysis indicated that the products of both genes displayed very similar structures, despite the low sequence similarity. In silico screening revealed a specific duplication of the hemolysin gene restricted to serotypes C and D of C. botulinum and their related species among thiol-activated hemolysin-producing bacteria. Our findings provide important insights into the genetic characteristics of pathogenic bacteria.

Multiple-locus variable number of tandem repeat analysis as a tool for molecular epidemiology of botulism: The Italian experience

Clostridium botulinum is the bacterial agent of botulism, a rare but severe neuro-paralytic disease. Because of its high impact, in Italy botulism is monitored by an ad hoc surveillance system. The National Reference Centre for Botulism, as part of this system, collects and analyzes all demographic, epidemiologic, microbiological, and molecular data recovered during cases and/or outbreaks occurred in Italy. A panel of 312 C. botulinum strains belonging to group I were submitted to MLVA sub-typing. Strains, isolated from clinical specimens, food and environmental samples collected during the surveillance activities, were representative of all forms of botulism from all Italian regions. Through clustering analysis isolates were grouped into 12 main clusters. No regional or temporal clustering was detected, demonstrating the high heterogeneity of strains circulating in Italy. This study confirmed that MLVA is capable of sub-typing C. botulinum strains. Moreover, MLVA is effective at tracing and tracking the source of contamination and is helpful for the surveillance system in terms of planning and upgrading of procedures, activities and data collection forms.

Neutralization of Botulinum Neurotoxin Type E by a Humanized Antibody

Botulinum neurotoxins (BoNTs) cause botulism and are the deadliest naturally-occurring substances known to humans. BoNTs have been classified as one of the category A agents by the Centers for Disease Control and Prevention, indicating their potential use as bioweapons. To counter bio-threat and naturally-occurring botulism cases, well-tolerated antibodies by humans that neutralize BoNTs are relevant. In our previous work, we showed the neutralizing potential of macaque (Macaca fascicularis)-derived scFv-Fc (scFv-Fc ELC18) by in vitro endopeptidase immunoassay and ex vivo mouse phrenic nerve-hemidiaphragm assay by targeting the light chain of the botulinum neurotoxin type E (BoNT/E). In the present study, we germline-humanized scFv-Fc ELC18 into a full IgG hu8ELC18 to increase its immunotolerance by humans. We demonstrated the protection and prophylaxis capacity of hu8ELC18 against BoNT/E in a mouse model. A concentration of 2.5 ng/mouse of hu8ELC18 protected against 5 mouse lethal dose (MLD) in a mouse protection assay and complete neutralization of 1 LD50 of pure BoNT/E toxin was achieved with 8 ng of hu8ELC18 in mouse paralysis assay. Furthermore, hu8ELC18 protected mice from 5 MLD if injected up to 14 days prior to intraperitoneal BoNT/E administration. This newly-developed humanized IgG is expected to have high tolerance in humans.

"Non-Toxic" Proteins of the Botulinum Toxin Complex Exert In-vivo Toxicity

The botulinum neurotoxin (BoNT) causes muscle paralysis and is the most potent toxin in nature. BoNT is associated with a complex of auxiliary “Non-Toxic” proteins, which constitute a large-sized toxin complex (L-TC). However, here we report that the “Non-Toxic” complex of serotype D botulinum L-TC, when administered to rats, exerts in-vivo toxicity on small-intestinal villi. Moreover, Serotype C and D of the “Non-Toxic” complex, but not BoNT, induced vacuole-formation in a rat intestinal epithelial cell line (IEC-6), resulting in cell death. Our results suggest that the vacuole was formed in a manner distinct from the mechanism by which Helicobacter pylori vacuolating toxin (VacA) and Vibrio cholerae haemolysin induce vacuolation. We therefore hypothesise that the serotype C and D botulinum toxin complex is a functional hybrid of the neurotoxin and vacuolating toxin (VT) which arose from horizontal gene transfer from an ancestral BoNT-producing bacterium to a hypothetical VT-producing bacterium.

Interneuronal Transfer and Distal Action of Tetanus Toxin and Botulinum Neurotoxins A and D in Central Neurons

Recent reports suggest that botulinum neurotoxin (BoNT) A, which is widely used clinically to inhibit neurotransmission, can spread within networks of neurons to have distal effects, but this remains controversial. Moreover, it is not known whether other members of this toxin family are transferred between neurons. Here, we investigate the potential distal effects of BoNT/A, BoNT/D, and tetanus toxin (TeNT), using central neurons grown in microfluidic devices. Toxins acted upon the neurons that mediated initial entry, but all three toxins were also taken up, via an alternative pathway, into non-acidified organelles that mediated retrograde transport to the somato-dendritic compartment. Toxins were then released into the media, where they entered and exerted their effects upon upstream neurons. These findings directly demonstrate that these agents undergo transcytosis and interneuronal transfer in an active form, resulting in long-distance effects.

Diversity of Group I and II Clostridium botulinum Strains from France Including Recently Identified Subtypes

In France, human botulism is mainly food-borne intoxication, whereas infant botulism is rare. A total of 99 group I and II Clostridium botulinum strains including 59 type A (12 historical isolates [1947-1961], 43 from France [1986-2013], 3 from other countries, and 1 collection strain), 31 type B (3 historical, 23 recent isolates, 4 from other countries, and 1 collection strain), and 9 type E (5 historical, 3 isolates, and 1 collection strain) were investigated by botulinum locus gene sequencing and multilocus sequence typing analysis. Historical C. botulinum A strains mainly belonged to subtype A1 and sequence type (ST) 1, whereas recent strains exhibited a wide genetic diversity: subtype A1 in orfX or ha locus, A1(B), A1(F), A2, A2b2, A5(B2') A5(B3'), as well as the recently identified A7 and A8 subtypes, and were distributed into 25 STs. Clostridium botulinum A1(B) was the most frequent subtype from food-borne botulism and food. Group I C. botulinum type B in France were mainly subtype B2 (14 out of 20 historical and recent strains) and were divided into 19 STs. Food-borne botulism resulting from ham consumption during the recent period was due to group II C. botulinum B4. Type E botulism is rare in France, 5 historical and 1 recent strains were subtype E3. A subtype E12 was recently identified from an unusual ham contamination. Clostridium botulinum strains from human botulism in France showed a wide genetic diversity and seems to result not from a single evolutionary lineage but from multiple and independent genetic rearrangements.

Diversity and Evolution in the Genome of Clostridium difficile

Clostridium difficile infection (CDI) is the leading cause of antimicrobial and health care-associated diarrhea in humans, presenting a significant burden to global health care systems. In the last 2 decades, PCR- and sequence-based techniques, particularly whole-genome sequencing (WGS), have significantly furthered our knowledge of the genetic diversity, evolution, epidemiology, and pathogenicity of this once enigmatic pathogen. C. difficile is taxonomically distinct from many other well-known clostridia, with a diverse population structure comprising hundreds of strain types spread across at least 6 phylogenetic clades. The C. difficile species is defined by a large diverse pangenome with extreme levels of evolutionary plasticity that has been shaped over long time periods by gene flux and recombination, often between divergent lineages. These evolutionary events are in response to environmental and anthropogenic activities and have led to the rapid emergence and worldwide dissemination of virulent clonal lineages. Moreover, genome analysis of large clinically relevant data sets has improved our understanding of CDI outbreaks, transmission, and recurrence. The epidemiology of CDI has changed dramatically over the last 15 years, and CDI may have a foodborne or zoonotic etiology. The WGS era promises to continue to redefine our view of this significant pathogen.

Clostridium difficile: New Insights into the Evolution of the Pathogenicity Locus

The major virulence factors of Clostridium difficile are toxins A and B. These toxins are encoded by tcdA and tcdB genes, which form a pathogenicity locus (PaLoc) together with three additional genes that have been implicated in regulation (tcdR and tcdC) and secretion (tcdE). To date, the PaLoc has always been found in the same location and is replaced in non-toxigenic strains by a highly conserved 75/115 bp non-coding region. Here, we show new types of C. difficile pathogenicity loci through the genome analysis of three atypical clinical strains and describe for the first time a variant strain producing only toxin A (A⁺B⁻). Importantly, we found that the PaLoc integration sites of these three strains are located in the genome far from the usual single known PaLoc integration site. These findings allowed us to propose a new model of PaLoc evolution in which two “Mono-Toxin PaLoc” sites are merged to generate a single “Bi-Toxin PaLoc”.

Pore-forming activity of clostridial binary toxins

Clostridial binary toxins (Clostridium perfringens Iota toxin, Clostridium difficile transferase, Clostridium spiroforme toxin, Clostridium botulinum C2 toxin) as Bacillus binary toxins, including Bacillus anthracis toxins consist of two independent proteins, one being the binding component which mediates the internalization into cell of the intracellularly active component. Clostridial binary toxins induce actin cytoskeleton disorganization through mono-ADP-ribosylation of globular actin and are responsible for enteric diseases. Clostridial and Bacillus binary toxins share structurally and functionally related binding components which recognize specific cell receptors, oligomerize, form pores in endocytic vesicle membrane, and mediate the transport of the enzymatic component into the cytosol. Binding components retain the global structure of pore-forming toxins (PFTs) from the cholesterol-dependent cytotoxin family such as perfringolysin. However, their pore-forming activity notably that of clostridial binding components is more related to that of heptameric PFT family including aerolysin and C. perfringens epsilon toxin. This review focuses upon pore-forming activity of clostridial binary toxins compared to other related PFTs. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.