Clostridium botulinum types C and D and the closely related Clostridium novyi:

Clostridium novyi’s Alpha-Toxin Changes Proteome and Phosphoproteome of HEp-2 Cells

C. novyi type A produces the alpha-toxin (TcnA) that belongs to the large clostridial glucosylating toxins (LCGTs) and is able to modify small GTPases by N-acetylglucosamination on conserved threonine residues. In contrast, other LCGTs including Clostridioides difficile toxin A and toxin B (TcdA; TcdB) modify small GTPases by mono-o-glucosylation. Both modifications inactivate the GTPases and cause strong effects on GTPase-dependent signal transduction pathways and the consequent reorganization of the actin cytoskeleton leading to cell rounding and finally cell death. However, the effect of TcnA on target cells is largely unexplored. Therefore, we performed a comprehensive screening approach of TcnA treated HEp-2 cells and analyzed their proteome and their phosphoproteome using LC-MS-based methods. With this data-dependent acquisition (DDA) approach, 5086 proteins and 9427 phosphosites could be identified and quantified. Of these, 35 proteins were found to be significantly altered after toxin treatment, and 1832 phosphosites were responsive to TcnA treatment. By analyzing the TcnA-induced proteomic effects of HEp-2 cells, 23 common signaling pathways were identified to be altered, including Actin Cytoskeleton Signaling, Epithelial Adherens Junction Signaling, and Signaling by Rho Family GTPases. All these pathways are also regulated after application of TcdA or TcdB of C. difficile. After TcnA treatment the regulation on phosphorylation level was much stronger compared to the proteome level, in terms of both strength of regulation and the number of regulated phosphosites. Interestingly, various signaling pathways such as Signaling by Rho Family GTPases or Integrin Signaling were activated on proteome level while being inhibited on phosphorylation level or vice versa as observed for the Role of BRCA1 in DNA Damage Response. ZIP kinase, as well as Calmodulin-dependent protein kinases IV & II, were observed as activated while Aurora-A kinase and CDK kinases tended to be inhibited in cells treated with TcnA based on their substrate regulation pattern.

Prevalent toxin types of Clostridium botulinum in South Korean cattle farms

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C. botulinum types B, C/D, and D are prevalent in South Korean cattle farms.

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Botulinum toxin type B is dominant in cow feeds in South Korean cattle farms.

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Botulinum toxin type D is dominant in cow feces in South Korean cattle farms.

Clostridium botulinum produces neurotoxic substrates that can cause fatal flaccid paralysis called botulism. These neurotoxins are classified into types A–G. Several botulism cases were recorded in 2012–2013 in the Gyeonggi province, South Korea. We assessed the distribution of C. botulinum types B, C, and D in several South Korean farms. A total of 184 samples collected in 2012–2013, including feces (n = 72), hay and silage (n = 50), soil (n = 26), water trough (n = 21), and stomach contents (n = 15), were subjected to multiplex polymerase chain reaction (PCR) to screen for types B, C, and D. Twenty-four samples tested PCR-positive as follows: type B (n = 11), type C/D (n = 4), and type D (n = 18). Eight of the 11 type B samples were detected in hay and silage. Sixteen of the 18 type D samples were detected in fecal and stomach content samples. PCR-positivity was observed in fecal (n = 9, 12.5%), hay and silage (n = 10, 20.0%), water trough (n = 2, 9.5%), and stomach content (n = 12, 80.0%) samples. Fourteen (42.4%) C. botulinum-positive samples were isolated from the PCR-positive samples (type B [n = 8], type C/D [n = 1], and type D [n = 5]). Our findings demonstrate that C. botulinum types B, C/D, and D were prevalent in South Korean cattle farms between 2012 and 2013.

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.

Equine grass sickness

Equine grass sickness (EGS; equine dysautonomia) is a polyneuronopathy affecting both the central and the peripheral nervous systems of horses. As the name implies, EGS almost exclusively affects grazing horses, resulting in the development of a characteristic array of clinical signs, most of which can be attributed to neuronal degeneration in the autonomic and enteric nervous systems. Varying disease severities occur, largely determined by the extent of neuronal degeneration in the myenteric and submucous plexuses of the enteric nervous system. Extensive neuronal degeneration, as seen in acute and subacute forms of EGS, results in intestinal dysmotility, the severity of which is incompatible with survival. In comparison, a proportion of chronic forms of EGS, characterised by less severe neuronal degeneration, will survive. Despite extensive research efforts since EGS was first reported over 100 years ago, the precise aetiology remains elusive. This article reviews much of the scientific literature on EGS, covering epidemiology, pathology, diagnosis, treatment and aetiological hypotheses.

Real-time PCR for Clostridium botulinum type C neurotoxin (BoNTC) gene, also covering a chimeric C/D sequence--application on outbreaks of botulism in poultry

In recent years, botulism type C has become a serious problem in poultry flocks in Sweden. A real-time PCR assay for Clostridium botulinum (C. botulinum) type C neurotoxin (BoNTC) gene was developed as an alternative to the mouse bioassay for detection and identification of C. botulinum type C. The complete method consists of an optimized enrichment protocol followed by automated DNA extraction prior to real-time PCR. The sensitivity of the PCR assay was determined with purified DNA to approximately 50 copies per PCR reaction. The specificity of the PCR assay was evaluated on a panel of about thirty relevant bacteria and on samples of caecum from birds collected in connection with botulism outbreaks on Swedish poultry farms. The PCR assay also covers a previously reported chimeric C/D sequence of the gene. Caecum samples from the outbreaks were positive by real-time PCR. Some of these samples were also examined with a set of conventional PCR methods, to distinguish the gene for the chimeric form from the conserved type C gene. Interestingly, the caecum samples were found to be positive for the chimeric C/D sequence. This is the first study in Europe demonstrating the chimeric C/D sequence. When the toxin gene in two of the samples was sequenced, it was closely identical (99-100%) with several previously reported C/D chimeric sequences. DNA extraction and the real-time PCR assay were both performed in a 96-well format, facilitating for future large-scale detection in outbreak situations and prevalence studies.

Comparison of IgG antibody levels to Clostridium botulinum antigens between euthanased and surviving cases of chronic grass sickness

Serum from 12 horses suffering from chronic grass sickness (CGS) were assayed for IgG antibodies against botulinum neurotoxins C and D (BoNT/C and BoNT/D) and to a surface antigen extract of a neurotoxin negative strain of Clostridium botulinum type C. Collectively, the six surviving CGS cases demonstrated significantly higher initial IgG levels (P=0.05) against surface antigens than the six that were subsequently euthanased. The surviving animals also demonstrated higher initial IgG levels against the BoNT/C but not reaching significance (P=0.06). The two groups demonstrated no difference between IgG levels against BoNT/D. This study supports existing evidence of the involvement of C. botulinum type C in the aetiology of grass sickness.

A PCR approach to determine the distribution of toxin genes in closely related Clostridium species: Clostridium botulinum type C and D neurotoxins and C2 toxin, and Clostridium novyi alpha toxin

The closely related Clostridium novyi and Clostridium botulinum types C and D are of current interest because of their association with serious infections in injecting drug users (C. novyi type A) and equine and feline dysautonomias (C. botulinum types C/D). The species are defined by the major toxins they produce: the alpha toxin of C. novyi, and the type C and D neurotoxins of C. botulinum (BoNT/C and BoNT/D). The other major toxin produced by this group, and previously thought to be restricted to the botulinum types, is the chromosomally encoded C2--a binary toxin consisting of two components, I and II. In the current study 44 of these clostridia from the authors' culture collection were investigated--most of which had been identified previously by conventional biochemical tests as 'C. novyi type A'. The aim was to check the distribution of toxin genes by PCR to see if the identities were consistent with the genes carried, and to ascertain if the C2 gene was only found in authentic C. botulinum strains. Several combinations of the species-defining genes and the two components of the C2 genes were detected. Only the authentic BoNT/C- and BoNT/D-positive C. botulinum strains and one of two non-neurotoxic variants of type C carried genes for both components of the C2 toxin. Of the remaining 40 C. novyi type A-like strains, the gene for the alpha toxin was found in 22, with 19 of these also possessing the gene for component I (16) or component II (3) but not both. In the alpha toxin-negative strains (22), both of the C2 genes were detected in 5 strains (3 C. botulinum), with component I in 11 strains and neither gene in 6 strains.

Identification of Clostridium species and DNA fingerprinting of Clostridium perfringens by amplified fragment length polymorphism analysis

An amplified fragment length polymorphism (AFLP) method was applied to 129 strains representing 24 different Clostridium species, with special emphasis on pathogenic clostridia of medical or veterinary interest, to assess the potential of AFLP for identification of clostridia. In addition, the ability of the same AFLP protocol to type clostridia at the strain level was assessed by focusing on Clostridium perfringens strains. All strains were typeable by AFLP, so the method seemed to overcome the problem of extracellular DNase production. AFLP differentiated all Clostridium species tested, except for Clostridium ramosum and Clostridium limosum, which clustered together with a 45% similarity level. Other Clostridium species were divided into species-specific clusters or occupied separate positions. Wide genetic diversity was observed among Clostridium botulinum strains, which were divided into seven species-specific clusters. The same AFLP protocol was also suitable for typing C. perfringens at the strain level. A total of 29 different AFLP types were identified for 37 strains of C. perfringens; strains initially originating from the same isolate showed identical fingerprinting patterns and were distinguished from unrelated strains. AFLP proved to be a highly reproducible, easy-to-perform, and relatively fast method which enables high throughput of samples and can serve in the generation of identification libraries. These results indicate that the AFLP method provides a promising tool for the identification and characterization of Clostridium species.

Structure of botulinum neurotoxin type D light chain at 1.65 A resolution: repercussions for VAMP-2 substrate specificity

The seven serotypes (A-G) of botulinum neurotoxins (BoNTs) function through their proteolytic cleavage of one of three proteins (SNAP-25, Syntaxin, and VAMP) that form the SNARE complex required for synaptic vesicle fusion. The different BoNTs have very specific protease recognition requirements, between 15 and 50 amino acids in length depending on the serotype. However, the structural details involved in substrate recognition remain largely unknown. Here is reported the 1.65 A resolution crystal structure of the catalytic domain of BoNT serotype D (BoNT/D-LC), providing insight into the protein-protein binding interaction and final proteolysis of VAMP-2. Structural analysis has identified a hydrophobic pocket potentially involved in substrate recognition of the P1' VAMP residue (Leu 60) and a second remote site for recognition of the V1 SNARE motif that is critical for activity. A structural comparison of BoNT/D-LC with BoNT/F-LC that also recognizes VAMP-2 one residue away from the BoNT/D-LC site provides additional molecular details about the unique serotype specific activities. In particular, BoNT/D prefers a hydrophobic interaction for the V1 motif of VAMP-2, while BoNT/F adopts a more hydrophilic strategy for recognition of the same V1 motif.

Two cases of equine grass sickness with evidence for soil-borne origin involving botulinum neurotoxin

Botulism is caused by different types of Clostridium botulinum, a soil bacterium. Equine grass sickness (equine dysautonomia) is suspected of being a clinical form of this disease. On a stud where this disease occurred twice within 8 months, grass and soil samples and necropsy specimens of one horse were tested for the presence of bacterial forms and toxin of C. botulinum. Different types and type mixtures (A-E) of C. botulinum and botulinum neurotoxin were found. For the first time, it has been shown that green grass blades contain botulinum toxin. The results support the hypothesis that equine grass sickness is a clinical form of botulism, a soil-borne disease.