Quantification of Clostridium botulinum toxin gene expression by competitive reverse transcription-PCR

Clostridium botulinum produces a characteristic botulinum neurotoxin which can cause an often fatal neuroparalytic condition known as botulism. Although food-borne botulism is rare, critical screening by food companies is necessary to ensure that food products are safe. At present, the food industry assesses the risks of botulinum neurotoxin production by challenge testing to check any new food products and to check the efficacy of new storage regimes. Challenge testing involves artificial introduction of defined strains of microorganisms into food, and microbial growth and possible toxin production are then monitored. Botulinum toxin is normally analyzed by using the mouse bioassay. However, the mouse bioassay is expensive, slow, and politically sensitive because of animal rights issues. In this paper we describe adaptation of a new assay, competitive reverse transcription-PCR (RT-PCR), to monitor botulinum neurotoxin production. This method accurately measures the level of toxin-encoding mRNA in C. botulinum cells. Measurement of mRNA should provide a good indication of gene expression as mRNA is turned over rapidly in bacterial cells. In addition, the method is rapid, specific, and sensitive. The competitive RT-PCR method was developed to examine C. botulinum E VH toxin gene expression and was used to investigate the level of toxin production by C. botulinum E VH when the organism was grown in two different types of broth. The results which we obtained with the competitive RT-PCR method demonstrated that this method is more rapid and more sensitive than the mouse bioassay.

Infantile botulism: clinical and laboratory observations of a rare neuroparalytic disease

A 3-month-old male infant was admitted to the University Hospital of Los Andes with a history of constipation, weak crying, poor feeding, flaccidity and later bilateral ptosis and hyporeflexia. The admission diagnosis was septicaemia until an electrophysiological study reported postetanic facilitation with 50 Hz/seg stimulations four days later. The Clostridium botulinum toxin type B was isolated from the infant's stool samples and the organism grew in anaerobic cultures. The patient recovered completely and was discharged 2 months later. Although infant botulism is an uncommon disease in our environment, this diagnosis must be suspected in all afebrile infants with constipation, affected cranial nerves and generalized hypotonia. The principal differential diagnoses are Landry-Guillain-Barré syndrome, poliomyelitis, myasthenia gravis and infant muscular atrophy.

The threat of biological terrorism: a public health and infection control reality

Bioterrorism is an emerging public health and infection control threat. Potential biological agents include smallpox, anthrax, plague, tularemia, botulinum toxin, brucellosis, Q fever, viral encephalitis, hemorrhagic fever, and staphylococcal enterotoxin B. An understanding of the epidemiology, clinical manifestations, and management of the more likely candidate agents is critical to limiting morbidity and mortality from a biological event. Effective response requires an increased index of suspicion for unusual diseases or syndromes, with prompt reporting to health authorities to facilitate recognition of an outbreak and subsequent intervention. Hospital epidemiology programs will play a crucial role in this effort.

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

A nested PCR was developed for detection of the Clostridium botulinum type C1 toxin gene in sediments collected from wetlands where avian botulism outbreaks had or had not occurred. The C1 toxin gene was detected in 16 of 18 sites, demonstrating both the ubiquitous distribution of C. botulinum type C in wetland sediments and the sensitivity of the detection assay.

Development of in vitro assays for the detection of botulinum toxins in foods

Currently the only accepted method for the detection of botulinum neurotoxin in contaminated samples is the mouse bioassay. Although highly sensitive this test has a number of drawbacks: it is expensive to perform, lacks specificity and involves the use of animals. With increasing resistance to such animal tests there is a need to replace the bioassay with a reliable in vitro test. Over the past six years it has been demonstrated that all the botulinum neurotoxins act intracellularly as highly specific zinc endoproteases, cleaving proteins involved in the control of secretion of neurotransmitters. In the work described, this enzymatic activity has been utilised in assay formats for the detection in foods of neurotoxin of the serotypes involved in food-borne outbreaks in man. These assays have been shown to have a greater sensitivity, speed and specificity than the mouse bioassay. It is envisaged that such assays will prove realistic alternatives to animal-based tests.

Biodiversity of Clostridium botulinum type E strains isolated from fish and fishery products

The genetic biodiversity of Clostridium botulinum type E strains was studied by pulsed-field gel electrophoresis (PFGE) with two macrorestriction enzymes (SmaI-XmaI and XhoI) and by randomly amplified polymorphic DNA (RAPD) analysis with two primers (OPJ 6 and OPJ 13) to characterize 67 Finnish isolates from fresh fish and fishery products, 15 German isolates from farmed fish, and 10 isolates of North American or North Atlantic origin derived mainly from different types of seafood. The effects of fish species, processing, and geographical origin on the epidemiology of the isolates were evaluated. Cluster analysis based on macrorestriction profiles was performed to study the genetic relationships of the isolates. PFGE and RAPD analyses were combined and resulted in the identification of 62 different subtypes among the 92 type E isolates analyzed. High genetic biodiversity among the isolates was observed regardless of their source. Finnish and North American or North Atlantic isolates did not form distinctly discernible clusters, in contrast with the genetically homogeneous group of German isolates. On the other hand, indistinguishable or closely related genetic profiles among epidemiologically unrelated samples were detected. It was concluded that the high genetic variation was probably a result of a lack of strong selection factors that would influence the evolution of type E. The wide genetic biodiversity observed among type E isolates indicates the value of DNA-based typing methods as a tool in contamination studies in the food industry and in investigations of botulism outbreaks.

Ribotyping as an identification tool for Clostridium botulinum strains causing human botulism

Ribotyping was used for characterisation of 68 Clostridium botulinum strains and five related Clostridium species to determine the applicability of this method for identification of species causing human botulism. Thirteen restriction enzymes were initially tested for suitability for ribotyping of C. botulinum, of which EcoRI and HindIII were selected. Both enzymes clearly differentiated between proteolytic (group I) and a nonproteolytic (group II) strains of C. botulinum, and can be recommended for Group/species identification. Using a commercial software package (GelCompar), a numerical analysis of the discriminatory abilities of EcoRI and HindIII ribotyping within and between the two C. botulinum groups was performed. EcoRI had the higher discriminatory index (0.982), but the ribopatterns generated with group II strains were partly muddled and difficult to interpret. All HindIII ribopatterns were easy to analyse and the discriminatory index for all strains was almost equally high (0.954), whereas this enzyme did not discriminate well between group I isolates. The Clostridium strains diverged at 35+/-13% (mean+/-standard deviation) Dice similarity in dendrograms based on cluster analysis of the ribotyping results. These findings are in good agreement with taxonomical ribotyping studies with other bacterial genera, indicating that ribotyping is a highly suitable method for C. botulinum species identification.

Isolation and characterisation of neurotoxigenic Clostridium butyricum from soil in China

Soil specimens collected from a site around the home of patients with food-borne type E. botulism probably caused by neurotoxigenic Clostridium butyricum in Guanyun, Jiangsu province, China, were examined for the presence of neurotoxigenic C. butyricum. Five lakeside sites of Weishan lake, in an area near to the sites where the type E. botulism outbreaks caused by neurotoxigenic C. butyricum occurred were also surveyed. Type E toxin-producing C. butyricum was isolated from soil from four sites including the site in Guanyun. Polymerase chain reaction assay demonstrated the presence of the type E toxin gene in all the toxigenic isolates. The biochemical properties of the isolates from the Guanyun soil and the lakeside soil were identical except for inulin fermentation and starch hydrolysis properties. These results indicate that neurotoxigenic C. butyricum has its principal habitat in soil.

[Botulism. Summary based on six cases]

Botulism is a rare neuroparalytic disease caused by neurotoxins of Clostridium species. In Hungary it most commonly occurs as a foodborne illness with ocular and bulbar paralysis, muscle weakness and gastrointestinal symptoms. Six cases of botulism were observed by the authors, first in 1993 five members of a family, then in 1997 a patient with sporadic illness. The diagnosis was confirmed by toxin tests in addition to the symptoms and food history. Recognition of the epidemiologic associations proved very useful in the confirmation of outbreak-related cases. The illness was moderately serious at three patients and mild at two patients. One of the patients had a cirrhosis of the liver, and her status became critical because of the repeated bleeding from oesophagus varicose vein. The patient with sporadic illness had a serious gastric dilatation and palsy of bowels causing paralytic ileus at the start of the illness. The symptoms regressed slowly, roughly in three weeks, at all patients. Death did not happened. After the case reports the authors review the disease-microorganism, toxin, clinical entities, incidence, symptoms, diagnosis, differential-diagnosis, and finally the treatment.

Characterization of Clostridium botulinum type B neurotoxin associated with infant botulism in japan

The neurotoxin of strain 111 (111/NT) associated with type B infant botulism showed antigenic and biological properties different from that (Okra/NT) produced by a food-borne botulism-related strain, Okra. The specific toxicity of 111/NT was found to be about 10 times lower than that of Okra/NT. The monoclonal antibodies recognizing the light chain cross-reacted with both neurotoxins, whereas most of the antibodies recognizing the carboxyl-terminal half of the heavy chain of Okra/NT did not react to 111/NT. Binding experiments with rat brain synaptosomes revealed that 125I-labeled 111/NT bound to a single binding site with a dissociation constant (Kd) of 2.5 nM; the value was rather lower than that (0.42 nM) of 125I-Okra/NT for the high-affinity binding site. In the lipid vesicles reconstituted with ganglioside GT1b, 125I-Okra/NT interacted with the amino-terminal domain of synaptotagmin 1 (Stg1N) or synaptotagmin 2 (Stg2N), fused with the maltose-binding protein, in the same manner as the respective full-length synaptotagmins, and the Kd values accorded with those of the low- and high-affinity binding sites in synaptosomes. However, 125I-111/NT only exhibited a low capacity for binding to the lipid vesicles containing Stg2N, but not Stg1N, in the presence of ganglioside GT1b. Moreover, synaptobrevin-2, an intracellular target protein, was digested to the same extent by the light chains of both neurotoxins in a concentration-dependent manner. These findings indicate that the 111/NT molecule possesses the receptor-recognition site structurally different from Okra/NT, probably causing a decreased specific toxicity.

Conservative prediction of time to Clostridium botulinum toxin formation for use with time-temperature indicators to ensure the safety of foods

Integrating-type time-temperature indicators (TTIs) may be utilized to warn food processors and consumers about storage conditions that may have rendered a food potentially hazardous. As an example of how integrated TTIs could be manufactured to emulate an infinite set of time-temperature situations, a set of conditions which have supported C. botulinum growth and toxin production was compiled. The time-temperature curve representing conservative times required for toxin formation was constructed with data from literature relating to toxin formation as a function of temperature in any media or food product. This set of critical time-temperature data is fit by a conservative empirical relationship that can be used to predict combinations of incubation times and storage temperatures that represent a potential health risk from C. botulinum in foods. A TTI could be constructed to indicate deviation from such a given set of conditions to bring attention to foods that may have been exposed to potentially hazardous temperatures with respect to C. botulinum toxin formation.

A large outbreak of botulism: the hazardous baked potato

In April 1994, the largest outbreak of botulism in the United States since 1978 occurred in El Paso, Texas. Thirty persons were affected; 4 required mechanical ventilation. All ate food from a Greek restaurant. The attack rate among persons who ate a potato-based dip was 86% (19/22) compared with 6% (11/176) among persons who did not eat the dip (relative risk [RR] = 13.8; 95% confidence interval [CI], 7.6-25.1). The attack rate among persons who ate an eggplant-based dip was 67% (6/9) compared with 13% (241189) among persons who did not (RR = 5.2; 95% CI, 2.9-9.5). Botulism toxin type A was detected from patients and in both dips. Toxin formation resulted from holding aluminum foil-wrapped baked potatoes at room temperature, apparently for several days, before they were used in the dips. Consumers should be informed of the potential hazards caused by holding foil-wrapped potatoes at ambient temperatures after cooking.

Infant botulism. The first culture-confirmed Danish case

Infant botulism is caused by intestinal colonization by Clostridium botulinum, C. barati or C. butyricum. Infant botulism has only rarely been reported outside the USA. A 3-month-old boy developed constipation, lethargy, feeding difficulties and descending, severe, symmetric weakness. He was breastfed but had also been fed honey. Supportive care led to complete recovery. The serum was positive for C. botulinum toxin type A-F (mouse toxin neutralization assay). A strain of C. botulinum producing toxin type A and E was identified in the stool. C. botulinum was identified in a jar of honey of the same brand as the honey fed to the patient.

Characterization of a neurotoxigenic Clostridium butyricum strain isolated from the food implicated in an outbreak of food-borne type E botulism

Neurotoxigenic Clostridium butyricum was isolated from the food implicated in an outbreak of clinically diagnosed type E botulism in China. PCR assay showed that the isolate (LCL 155) contained the type E botulinum toxin gene. This appears to be the first report of neurotoxigenic C. butyricum causing food-borne botulism.

Emergence of Clostridium botulinum type B-like nontoxigenic organisms in a patient with type B infant botulism

We encountered a patient with infant botulism caused by a single clone of Clostridium botulinum type B. In the early convalescent phase, a C. botulinum type B-like nontoxigenic organism emerged in the feces instead. Growth inhibition of toxigenic strains by nontoxigenic strains was examined.

Application of nested polymerase chain reaction for the rapid diagnosis of infant botulism type B

A nested polymerase chain reaction was utilized to successfully detect the type B botulinum neurotoxin gene of Clostridium botulinum in feces from a 6-month-old patient, who had already been diagnosed with type B infant botulism by mouse bio-assay. This method of rapid diagnosis without enrichment culture of feces can be applied to other types of toxins in the use of the type-specific primers. Further investigations, however, are required to define the sensitivity and specificity of the method.

Avian botulism--another perspective

Waterfowl botulism is unique among intoxications because toxin produced within its victims leads to secondary poisoning of other birds. Because of this phenomenon, the epizootiology of the carcass-maggot cycle of botulism resembles that of an infectious disease and the reproductive rate (R) of the disease could be defined as the average number of secondary intoxications attributable to a single carcass introduced into a marsh. I propose that toxin production and botulism occur commonly at a low level in many marshes and that factors which influence R determine when the disease expands into a large epizootic. A model that incorporates the number of carcasses occurring in a marsh, the probability of a carcass containing spores, the probability of a carcass persisting until toxin-bearing maggots emerge, and the contact rate between live birds and toxin, may be useful for predicting the extent of secondary poisoning, for identifying questions for research, and as a theoretical basis for management.

The first case of type B infant botulism in Japan

A six-month-old girl with a 5 consecutive day history of constipation and poor feeding developed generalized weakness, poor head control, difficulties in sucking and swallowing, and cranial nerve dysfunction within a few days. These characteristic manifestations and clinical course prompted examination of the possibility of infant botulism, although no history of eating honey was obtained. Mouse bioassay performed with enema effluent demonstrated type B botulinum toxin. Culture of the effluent was positive for Clostridium botulinum type B. This is the first case of type B infant botulism in Japan.

Mosaic type of the nontoxic-nonhemaggulutinin component gene in Clostridium botulinum type A strain isolated from infant botulism in Japan

The gene encoding the nontoxic-nonhemaggulutinin (NTNH) component was amplified by the PCR technique using two primer sets and the DNA template from Clostridium botulinum type A strain 7I03-H isolated from infant botulism in Japan. The nucleotide sequence revealed that the NTNH gene was composed of 1,193 amino acids with a molecular weight of 130868.08. Furthermore, the N-terminal half side and C-terminal half side of the NTNH component were similar to the NTNH component of type C and type A, respectively. These results indicate that the NTNH component gene codes the mosaic NTNH component composed of type A and type C. The hemaggulutinin gene, aha, and ORF-22 gene, orf-22a, were undetectable in the region upstream of the NTNH component gene, ant. Therefore, orf-22a is not thought to play a key role in the expression of botulinum type A progenitor toxin gene.