In situ detection of the Clostridium botulinum type C1 toxin gene in wetland sediments with a nested PCR assay

A human-food web-animal interface on the prevalence of food-borne pathogens (Clostridia and Enterococcus) in mixed veterinary farms

In the present work, we addressed the impact of a human-food web-animal interface on the prevalence of food-borne pathogens in mixed farms of Tamil Nadu, India. We have isolated and identified six strains of Clostridium sp. and five strains of Enterococcus sp. from food and animal sources disposed near to the veterinary and poultry farms. Phylogenetic relationships of these strains were inferred from their homologies in 16S rDNA sequences and rRNA secondary structures. The strain PCP07 was taxonomically equivalent to C. botulinum confirmed by neurotoxin-specific PCR primers, followed by mouse bioassay. Other Clostridial and Enterococcal isolates have shown a phylogenetic similarity to the C. bifermentans and E. durans isolated from veterinary farms, respectively. Results of our study revealed that a human-food web-animal interface has influenced the disease incidence and prevalence of these isolates in the poultry to veterinary farms, where human food acted as a likely transmittance vehicle for their infections.

Molecular tools to detect anatoxin-a genes in aquatic ecosystems: Toward a new nested PCR-based method

Over the last few decades, cyanobacterial mass occurrence has become a recurrent feature of aquatic ecosystems. This has led to ecosystem exposure and health hazards associated with cyanotoxin production. The neurotoxin anatoxin-a and its homologs can be synthesized by benthic cyanobacterial species in lotic systems, but also by planktonic lacustrine species such as Dolichospermum (also known as Anabaena). However, only a few studies have focused on anatoxin-a occurrence and its biosynthesis genes in freshwater lakes. The initial aim of this study was to evaluate the molecular tools available in the literature to detect anatoxin-a biosynthesis genes in lacustrine environments. Having tested different sets of PCR primers, we found that that some sets of primers, such as anxC, were too specific and did not amplify anatoxin-a biosynthesis genes in all producing strains. On the other hand, some sets of primers, such as atxoa, seemed not to be specific enough, amplifying numerous non-specific bands in environmental samples, especially those from sediments. Furthermore, anaC and anaF amplification exhibited different band intensities during electrophoresis, suggesting a high variation in number of gene copies between samples. As a result, we proposed a new nested PCR-based method which considerably improved the amplification of the anaC gene in our environmental samples, eliminating non-specific bands and weak detections. Using this tool, our study also highlighted that anatoxin-a genes are widely distributed throughout freshwater lakes. This suggests the need for further ecological investigations into anatoxin-a in these ecosystems.

Relationship between gastrointestinal dysbiosis and Clostridium botulinum in dairy cows

The gastrointestinal tract is a balanced ecosystem that can get out of balance and predisposed to clostridial diseases or other pathological conditions. The objective of the present study was to evaluate the gut microbiota in dairy cows suffering from chronic botulism. Cows were investigated for Clostridium (C.) botulinum in faeces and rumen fluids. In order to study the relationship between botulism and gastrointestinal microbiota, faeces and rumen fluid were tested for bacterial composition using conventional microbiological culture techniques and fluorescence in situ hybridization (FISH). Protozoa were analyzed in rumen fluid microscopically. The presence of C. botulinum was associated with specific changes in the faecal microbiota, especially a significant reduction of total aerobic bacteria, total anaerobic bacteria, enterococci, Clostridium perfringens and yeast and fungi. Also C. botulinum positive rumen fluid had significantly more Bacteroides spp., C. histolyticum group, Alfa- proteobacteria, Gammaproteobacteria, and sulfate-reducing bacteria; as well as significantly fewer Euryaracheota, and the protozoa Epidinium spp. Dasytricha spp., Diplodiniinae spp. and Ophryoscolex spp. In conclusion, C. botulinum is common in dairy cows in Germany but the incidence of botulism is associated with microbial changes and composition in the gastrointestinal tract. Bacteria, yeast and protozoa appear to be crucial in the colonization process; however, the chronology of these events and role of each microbial group needs further evaluation.

Type C botulism in a commercial turkey farm: a case report

Botulism is an intoxication caused by exotoxins of Clostridium botulinum. The case of botulism described here occurred on a commercial meat turkey farm with two houses. Toms and hens were maintained in two separate houses, toms in house A and hens in house B. At 10 wk of age, an increase in mortality was observed in the toms located in house A. Clinically the animals presented with paralysis of the legs, wings, and neck. Affected birds were sitting and reluctant to move. Necropsy failed to find any specific lesions. In liver, heart, muscles, crop, and gizzard as well as in intestinal contents, DNA of C. botulinum type C was detected by PCR. The result was confirmed by a mouse lethality neutralization test. During the 2 wk after the onset of the clinical signs the mortality was about 12%. The hens kept in house B did not show any symptoms and remained healthy. Investigations of environmental samples to detect the source of the toxin were not successful. After 2 wk clinical signs and mortality abated. At 16 wk of age, toms again showed the same clinical signs accompanied by raised mortality. Again C. botulinum toxin type C was detected. Within 2 wk the total mortality reached roughly 50%. Based on the "precautionary principle" and in agreement with the local authorities, the birds were euthanatized using CO2 in order to not compromise food safety.

Visceral botulism at dairy farms in Schleswig Holstein, Germany: prevalence of Clostridium botulinum in feces of cows, in animal feeds, in feces of the farmers, and in house dust

From 41 dairy farms in Schleswig Holstein, Germany, 196 fecal specimens of diseased cows, 77 fecal specimens of farmers and family members from 26 of these farms, 35 animal feed specimens and 7 house dust specimens were investigated for Clostridium botulinum and its antigens, respectively. Four of the humans under study (one child, 8 month, and three adults) showed symptoms of infant/visceral botulism. Specimens were cultivated in reinforced clostridial medium (RCM). C. botulinum antigens were detected by ELISA. The aim of the study was to obtain information on the relationship of detected C. botulinum toxin-types in cows, in the feces of attending humans, and in the immediate environment. The results revealed that C. botulinum toxin-types were different for cows and humans. Toxin-type A was dominant in cow feces while type E was found in humans. Type E was also present in some animal feed specimens. Conversely, toxin-type A was prevalent in the house dust of farms. It may be assumed that the feeds were the source of human colonization with C. botulinum.

Diagnostic and possible therapeutic application of a monoclonal antibody (14G8) directed against botulinum type C neurotoxin

A monoclonal antibody, designated 14G8, detected Clostridium botulinum type C neurotoxin in immunoassays requiring native confirmation of the analyte. 14G8 bound to the light chain of the type C neurotoxin, which is conserved between strains of C. botulinum type C and C/d mosaic neurotoxins. 14G8 did not react to any other serotypes of C. botulinum neurotoxins. In mouse phrenic nerve-hemidiaphragm assays, 14G8, when combined with a second antibody (5D9-H9-A9, which reacts to epitopes on the carboxy terminus of the heavy chain), was able to protect the mouse myoneural junction from intoxication with C. botulinum type C neurotoxin. When used individually, both 14G8 and 5D9-H9-G9 antibodies slowed the loss of twitch tension in the mouse phrenic nerve-hemidiaphragm assays, but did not completely protect the phrenic nerve from paralysis. In in vivo mouse botulinum neurotoxin type C challenge studies, the combination of 14G8 and 5D9-H9-A9 significantly increased mean time-to-death and survival when compared to toxin controls and mice receiving only one of the monoclonal antibodies. These results suggest that the 14G8 monoclonal antibody could have useful therapeutic applications.

Real-time polymerase chain reaction for the detection of toxigenic Clostridium botulinum type C1 in waterbird and sediment samples

A quantitative real-time PCR (qPCR) for detection of the neurotoxin of the Clostridium botulinum type C (BoNTC) encoding gene has been compared with a nested PCR (nPCR) and a conventional PCR (cPCR) using 2 toxigenic C. botulinum C1 reference strains and samples from bird tissues (n = 30) and sediments (n = 30) from wetlands where botulism outbreaks have been reported. A cPCR based on 16S ribosomal RNA sequences from 60 strains of Clostridium species was also developed to detect the genomic DNA of C. botulinum C in order to evaluate the presence of nontoxigenic strains. Quantitative PCR showed a similar sensitivity to nPCR (<0.5 pg of DNA), and both were more sensitive than the cPCR when using the C. botulinum reference strains. Quantitative PCR and nPCR revealed an equal number of positives in uncultured samples of sediments (3%) and bird tissues (40%), but these values tended to be higher after culture enrichment with the qPCR assay (10% and 80%, respectively). Associations between the presences of toxigenic C. botulinum C in the environment and in birds within the ecological conditions in wetlands could be studied further using the culture enrichment and qPCR techniques shown in the current study.

Multiplex real-time PCR SYBR Green for detection and typing of group III Clostridium botulinum

Clostridium botulinum type C and type D belonging to the group III organisms, are mainly responsible for animal botulism outbreaks. Clinical signs alone are often insufficient to make a diagnosis of botulism and a laboratory confirmation is required. Laboratory confirmation can be performed by demonstrating the presence of botulinum neurotoxins in serum, gastrointestinal contents, liver, wound of sick or dead animals, or by demonstrating the presence of C. botulinum in gastrointestinal contents, liver, and wound. Demonstration of spores in gastrointestinal contents or tissue of animals with clinical signs indicative of botulism reinforces the clinical diagnosis. With the aim of detecting and typing C. botulinum group III organisms, a multiplex real-time PCR SYBR Green was developed and in-house validated. Selectivity, limit of detection, relative accuracy, relative specificity, relative sensitivity, and repeatability of the method were investigated. The multiplex real-time PCR SYBR green used showed a 100% selectivity, 100% relative accuracy, 100% relative specificity, 100% relative sensitivity and a limit of detection of 277 and 580 DNA copies for C. botulinum type C and C. botulinum type D, respectively. The method reported here represents a suitable tool for laboratory diagnosis of type C and D botulism and for testing a large number of samples collected during the animal botulism surveillance and prevention activities.

Fur animal botulism hazard due to feed

To assess the botulism hazard in fur animal feed production, 236 fur animal feed components and feed samples were analysed for Clostridium botulinum by detecting BoNT-encoding genes (botA, botB, botC, botE or botF) by PCR and for sulphite-reducing clostridia (SRC) by iron sulphite agar. The quality of the hazard analysis of critical control points (HACCP) -based in-house control system (IHCS) was evaluated with respect to botulism risk in feed plants (n=32). The overall prevalence of C. botulinum was 13% in different feed components and 5% in feed. The estimated MPN count of C. botulinum in feed components was 6.4 × 10(3)/kg at the highest and was shown to poorly correlate with SRC count. The critical control points in IHCSs were variable, and control limits were improperly set in most feed-producing plants. C. botulinum possesses a persistent safety hazard for fur animals by feed production, and control practices should be reassessed.

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.

Botulinum neurotoxin — from laboratory to bedside

Botulinum neurotoxin (BoNT) has been used clinically since 1980, with an ever-increasing range of clinical applications. This has coincided with a period of massively expanded interest in the underlying biology of the neurotoxin. Tremendous advances have taken place in the scientific understanding of neurotoxin structure and function since the description of their endopeptidase activity in 1992. These developments have led to an increased understanding of the mechanisms underpinning the clinical use of the neurotoxins and also in the technologies available to support their clinical use. The expanding range of clinical applications, and use in increasing doses, has also generated challenges for the clinicians and manufacturers of BoNT preparations to ensure continuing efficacy and safety margins for these new clinical settings. To date the increased clinical use of BoNTs has occurred largely empirically, and not by application of the recent insights into neurotoxin structure and function. With the increased knowledge regarding the biology of the neurotoxins, however, there is the opportunity to select preferred forms of the toxin for particular clinical applications and even to consider engineering the neurotoxins to produce modified products more suited to specific clinical applications. These developments and opportunities that have arisen, particularly over the last decade, emphasise the increasing need to maintain an active two way dialogue between clinicians and basic scientists to ensure that the advances in the laboratory are translated into clinical benefit and that the clinical developments in use of neurotoxin are supported by the scientific research activity. This article is based upon presentations given in a workshop at the 5th International Conference on Basic and Therapeutic Aspects of Botulinum and Tetanus Toxin in Denver in June, 2005 seeking to address issues relating to the laboratory/clinic interface.

Type C bovine botulism outbreak due to carcass contaminated non-acidified silage

The first reported bovine botulism outbreak in Finland is described. Nine out of 90 cattle on a dairy farm died after being fed non-acidified silage contaminated by animal carcasses. Type C botulinum neurotoxin gene was detected in one heifer by polymerase chain reaction (PCR) and the neurotoxin was detected by the mouse bioassay. Clostridium botulinum type C was isolated from liver samples. The isolated strain was identified with amplified fragment length polymorphism (AFLP) analysis as group III C. botulinum. To our knowledge, this is the first time that a type C bovine botulism outbreak has been diagnosed by PCR and confirmed by subsequent isolation and AFLP identification of the disease strain. The importance of the acidification process in silage production to inhibit C. botulinum toxin production in silage and thus to prevent further botulism outbreaks is emphasized. Nevertheless, preformed toxin in the carcass is not destroyed by acid.

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.

Persistence and mobility of a Clostridium botulinum spore population introduced to soil with spiked compost

In a recent study it could be shown that compost samples can contain Clostridium botulinum. It was investigated if C. botulinum introduced with compost into botulinum-free soil can persist and be translocated within the soil. Compost was spiked with two C. botulinum type D spore concentrations (10(3) and 10(5) spores g(-1)) and the composts were spread on an experimental site. Over a period of 939 days, samples were taken from the upper (0-5 cm) and the lower (10-30 cm) soil horizons. Physical and chemical as well as microbiological variables were measured. Clostridium botulinum spores were quantified in a culture MPN-PCR assay. On day 757 the last positive sample was obtained in the plots with the lower spore concentration (10(3) g(-1)). The bacteria were never detected in the samples taken from the lower horizons of these plots. Clostridium botulinum persisted over the whole investigation period in the plots which were treated with compost spiked with 10(5) spores g(-1). The concentrations found were between 20 and 20,000 spores g(-1) soil. The bacteria were vertically translocated and could be found in the lower soil horizons (20-2000 spores g(-1) soil) starting 70 days after the compost was spread.

Characterization of the neurotoxin produced by isolates associated with avian botulism

Several varieties of birds are affected by type C botulism. We conducted neutralization tests of culture supernatants of isolates from cases of avian botulism. Whereas the toxin produced by isolates derived from mammalian botulism was neutralized only with type C antitoxin, the toxins of all isolates related to avian botulism were neutralized with both type C and D antitoxins. An analysis of nucleotide sequences with several strains revealed that the neurotoxin gene in the isolates from avian botulism comprises two thirds of the type C neurotoxin gene and one third of the type D neurotoxin gene. This indicates that the neurotoxin of avian isolates is a mosaic of type C and D neurotoxins. We prepared three sets of primers to differentiate the gene for the mosaic form from the conserved genes of type C and D neurotoxins. The results of polymerase chain reaction with these primers indicated that all avian botulism-related isolates and specimens possess the gene for the mosaic form of the neurotoxin. The toxins purified from avian and mammalian isolates exhibited the same degree of lethality in mice, but the former showed greater toxicity to chickens than the latter. These results indicate that the mosaic neurotoxin is probably a pathogenic agent causing some forms of avian botulism.

Type C botulism due to toxic feed affecting 52,000 farmed foxes and minks in Finland

The largest reported outbreak of type C botulism in fur production animals is described. Epidemiological investigation of 117 out of 157 (response rate, 74.5%) farms revealed that 44,130 animals died or were euthanized, while 8,033 animals with milder symptoms recovered. The overall death rate in all animals at risk was 21.7%. The death rates were significantly higher in blue and shadow foxes (24.2 and 27.8%, respectively) than in silver and blue silver foxes and minks (below 4%). All minks had been immunized against botulinum toxin type C. Deaths were associated with feed manufactured by a local processor, 83 of whose customer farms (70.9%) reported dead or sick animals. Five feedlots out of 19 delivered to the farms on the day preceding the onset of the outbreak (day 2) were associated with a death rate higher than 40%. These feedlots consisted of fresh feed processed on day 2 and feed processed 1 day earlier (day 1). In laboratory analysis, the day 2 feed contained botulinum toxin type C (>600 minimum lethal doses/g), while the day 1 feed did not contain toxin. Toxin was not detected in feed raw-material samples. Clostridium botulinum type C was detected by PCR in some feed components and in feed. However, as the feed temperature was continuously 8 degrees C or below and the pH was continuously 5.6 or below according to the manufacturer, it seems unlikely that spore germination and toxin formation occurred during overnight storage. Hence, the events leading to toxin formation were not determined.

Botulism in the horse

Botulism should be considered in cases where weakness, paralysis, or intolerance to exercise might be seen in the horse. Dysphagia may also be present, although it is not a consistent finding. Potential sources include carrion in hay, moldy or otherwise rotted vegetation or forage, birds carrying material from animal burial or other similar sites, and contaminated carcasses on-site. Horses, especially foals, may also suffer from toxicoinfectious botulism, a condition where the C. botulinum might colonize and produce toxin within the gastrointestinal tract. Wounds also may harbor the organism and otherwise promote botulism. Diagnosis of botulism is often a clinical diagnosis backed up by elimination of other possible infectious, injurious, or toxic causes of weakness of the horse. Definitive diagnosis and type identification in the laboratory are difficult and usually require a suitable sample of the source material. Treatment often is unrewarding unless a case is identified early and the proper antitoxin is readily available. Prevention involves common sense approaches to feeding and care of the horse and, where possible, judicious use of vaccination in endemic areas.

Development of a combined selection and enrichment PCR procedure for Clostridium botulinum Types B, E, and F and its use to determine prevalence in fecal samples from slaughtered pigs

A specific and sensitive combined selection and enrichment PCR procedure was developed for the detection of Clostridium botulinum types B, E, and F in fecal samples from slaughtered pigs. Two enrichment PCR assays, using the DNA polymerase rTth, were constructed. One assay was specific for the type B neurotoxin gene, and the other assay was specific for the type E and F neurotoxin genes. Based on examination of 29 strains of C. botulinum, 16 strains of other Clostridium spp., and 48 non-Clostridium strains, it was concluded that the two PCR assays detect C. botulinum types B, E, and F specifically. Sample preparation prior to the PCR was based on heat treatment of feces homogenate at 70 degrees C for 10 min, enrichment in tryptone-peptone-glucose-yeast extract broth at 30 degrees C for 18 h, and DNA extraction. The detection limits after sample preparation were established as being 10 spores per g of fecal sample for nonproteolytic type B, and 3.0 x 10(3) spores per g of fecal sample for type E and nonproteolytic type F with a detection probability of 95%. Seventy-eight pig fecal samples collected from slaughter houses were analyzed according to the combined selection and enrichment PCR procedure, and 62% were found to be PCR positive with respect to the type B neurotoxin gene. No samples were positive regarding the type E and F neurotoxin genes, indicating a prevalence of less than 1.3%. Thirty-four (71%) of the positive fecal samples had a spore load of less than 4 spores per g. Statistical analysis showed that both rearing conditions (outdoors and indoors) and seasonal variation (summer and winter) had significant effects on the prevalence of C. botulinum type B, whereas the effects of geographical location (southern and central Sweden) were less significant.