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A review of WHO International Standards for botulinum antitoxins.

Clostridium botulinum produces the most potent known toxins, with seven distinct serotypes currently defined (A-G). These toxins can cause a life threatening systemic toxicity whether through natural causes such as food poisoning, infant botulism, wound botulism, or through use as bio-terror agents (e.g. inhalational botulism). It was realised early on that standard reference botulinum antitoxins were required to reduce the variation between assays and ensure a consistent potency of therapeutic antitoxins and vaccines, and to define the serotype. This led to the International Unit being defined by the World Health Organisation (WHO) in the 1960s with the establishment of the first International Standards (IS) for serotypes A-F. Since then botulinum antitoxin ISs have been used world wide as the 'yard stick' to measure the neutralising potency of antitoxins. These primary WHO ISs are used to calibrate in house working reagents that are more extensively utilised. A definition of the International Unit for serotype G antitoxin has yet to be defined or accepted by the WHO and urgently needs addressing. However, before September 11th 2001 there was very little interest in botulinum antitoxin IS and as a result stocks of most of the original preparations are now completely exhausted or depleted and replacements long overdue. We have reviewed the extensive history and availability of the primary WHO ISs and interim materials. All type A and B antitoxin materials were recently assayed and their relative activities confirmed against the original IS preparations. The recent increase in demand for these materials has further exacerbated the shortage. We describe here the production and characterization of stable freeze dried potential candidate replacements along with a new prospective first IS for type G antitoxin. Available toxin A reference preparations are also briefly reviewed.

Animals↗

Titration of botulinum antitoxin of low levels by the score method.

Botulinum antitoxin is commonly titrated by injecting a mixture of toxin and antitoxin into mice and by utilizing deaths as a marker to measure the amount of unneutralized toxin. We attempted to titrate antitoxin by converting the severity of symptoms (notably palsy) and time-to-death in days into scores. In neutralization tests with toxin levels at 5.9 LD50 and 23.5 LD50, a linear relationship was obtained for antitoxin dose in a range between 0.03 to 0.003 IU/ml. Statistical analysis showed that homogeneity of variance or slope was not denied for the scores obtained on any day from the first to the fourth days after injection, demonstrating that this method can titrate accurately antitoxin of such a low level as 0.003 IU/ml within 4 days after injection.

Animals↗

Botulinum antitoxins and antibacterial IgM and IgG antibodies in sera of persons immunized with botulinum polytoxoid combined with cholera vaccine. II. Response to cholera vaccine.

The response of humans to cholera vaccine was very heterogeneous. The proportion of IgG vibriocidal antibodies was high in persons having previous natural or artificial contact with V. cholerae antigens. Predominance of IgM antibody response was seen in persons vaccinated for the first time. This type of response was sometimes evoked by unspecific stimuli such as botulinum polytoxoid without cholera vaccine. Antibodies passively protecting mice were found both in IgM and IgG globulins but the activity of these antibodies was higher in IgG than in IgM globulins.

Adult↗

Botulinum antitoxins and antibacterial IgM and IgG antibodies in sera of persons immunized with botulinum polytoxoid combined with cholera vaccine. I. Response to botulinum toxoid.

Two groups of subjects were immunized with combined vaccine containing aluminum hydroxide-adsorbed botulinum toxoids, types A, B, and E, and 4 mld of formaldehyde-inactivated V. cholerae Inaba and Ogawa organisms. The first group included laboratory workers who were previously immunized against cholera and had professional contact with botulinum toxins and viable V. cholerae organisms. The second group included young men who were never vaccinated against botulism or cholera. The three-dose immunization schedule with combined vaccine resulted in clear-cut antitoxin response; after the third dose, the A, B, and E antitoxin level ranged from 0-2 to 10 IU/ml. Immunity against botulinum toxins lasted at least one year. Distribution of the antitoxins among IgM and IgG globulin classes resembled that in the case of response to other toxoids; 21 days after the third immunization antitoxin activity was found in IgG globulins.

Adult↗

In vitro assays for botulinum toxin and antitoxins.

Clostridium botulinum produces several powerful neuroparalytic toxins which, although rare in food-poisoning instances, are generally fatal. A considerable amount of effort has therefore been made by the food industry to ensure that food treatment processes adequate to prevent growth and toxin production by Cl. botulinum. Laboratory mice and guinea-pigs are presently used extensively both for the assay of botulinum toxins and for the development and assessment of vaccines used to protect laboratory workers. An amplified ELISA, using a monoclonal antibody, has been developed for botulinum type A toxin with a sensitivity similar to that of the mouse acute toxicity test. The immunoassay has been found to be applicable to the detection of toxin in foodstuffs and could replace the currently used mouse bioassay in many laboratories. Immunoassays have also been developed for the detection of antibodies to botulinum toxins. A preliminary study has shown that antibody titres to botulinum types A and B toxins in sera taken from immunised personnel, as measured by ELISA, showed limited correlation with those measured by the toxin neutralisation test in mice. A more extensive study should determine whether the latter test can be replaced by the ELISA.

Animal Testing Alternatives↗

Botulism.

Botulinum toxin is the most potent toxin known to humans and as little as 100 ng can be lethal. The toxin blocks peripheral cholinergic neurotransmission at the neuromuscular junction and cholinergic autonomic nervous system by introducing an endopeptadase enzyme into the presynaptic side of the synapse. The endopeptadase cleaves acetylcholine vesicle docking proteins that are required for the synapse to release acetylcholine into the synaptic cleft. Botulism occurs from consumption or inhalation of preformed botulinum toxin or growth of Clostridium botulinum bacteria in the infant gastrointestinal tract or within a wound. Growth of C. botulinum in the immature gut or wound will release botulinum toxin that reaches the circulation. All forms of botulism cause progressive weakness, bulbar signs (blurred vision, diplopia, mydriasis, dysphagia, and dysarthria), and respiratory failure with normal sensation and mentation. Treatment is aimed at 1) maintaining respiration via intubation and mechanical ventilation, 2) stopping progression of weakness by administration of botulinum antitoxin (equine trivalent botulinum antitoxin for adults and botulism immune-globulin intravenous-human for infant botulism), and 3) preventing complications from weeks of paralysis with good supportive care. The source of the botulinum toxin should be identified to prevent additional cases. Patients can recover normal muscle strength within weeks to months, but usually complain of fatigue for years.

Journal Article↗

A case of type F botulism in southern California.

BACKGROUND: Botulism caused by type F botulinum toxin accounts for less than 0.1% of all human botulism cases and is rarely reported in the literature. CASE REPORT: A 45-year-old woman presented to an emergency department complaining of blurred vision, difficulty focusing, and dysphagia. The treating physician initially considered the possibility of paralytic shellfish poisoning due to a report of shellfish ingestion, which was later determined to be frozen shrimp and a can of tuna, but no gastroenteritis or paresthesias were present. During the emergency department observation, the patient developed respiratory distress with hypercapnea and required intubation and mechanical ventilation. Within hours, ptosis, mydriasis, and weakness in the arms and legs developed. Bivalent (A, B) botulinum antitoxin was administered approximately 24 h from the onset of initial symptoms, but over the next two days complete paralysis progressed to the upper and lower extremities. Shortly thereafter a stool toxin assay demonstrated the presence of type F botulinum toxin. The patient subsequently received an experimental heptavalent botulinum antitoxin on hospital day 7 but paralysis was already complete. Her three-week hospital course was complicated by nosocomial pneumonia and a urinary tract infection, but she gradually improved and was discharged to a rehabilitation facility. Anaerobic cultures and toxin assays have yet to elucidate the source of exposure. CONCLUSION: We report a rare case of type F botulism believed to be foodborne in etiology. Administration of bivalent botulinum antitoxin did not halt progression of paralysis.

Animals↗

An outbreak of botulism in Thailand: clinical manifestations and management of severe respiratory failure.

BACKGROUND: Northern Thailand's biggest botulism outbreak to date occurred on 14 March 2006 and affected 209 people. Of these, 42 developed respiratory failure, and 25 of those who developed respiratory failure were referred to 9 high facility hospitals for treatment of severe respiratory failure and autonomic nervous system involvement. Among these patients, we aimed to assess the relationship between the rate of ventilator dependence and the occurrence of treatment by day 4 versus day 6 after exposure to bamboo shoots (the source of the botulism outbreak), as well as the relationship between ventilator dependence and negative inspiratory pressure. METHODS: We reviewed the circumstances and timing of symptoms following exposure. Mobile teams treated patients with botulinum antitoxin on day 4 or day 6 after exposure in Nan Hospital (Nan, Thailand). Eighteen patients (in 7 high facility hospitals) with severe respiratory failure received a low- and high-rate repetitive nerve stimulation test, and negative inspiratory pressure was measured. RESULTS: Within 1-65 h after exposure, 18 of the patients with severe respiratory failure had become ill. The typical clinical sequence was abdominal pain, nausea and/or vomiting, diarrhea, dysphagia and/or dysarthria, ptosis, diplopia, generalized weakness, urinary retention, and respiratory failure. Most patients exhibited fluctuating pulse and blood pressure. Repetitive nerve stimulation test showed no response in the most severe stage. In the moderately severe stage, there was a low-amplitude compound muscle action potential with a low-rate incremented/high-rate decremented response. In the early recovery phase, there was a low-amplitude compound muscle action potential with low- and high-rate incremented response. In the ventilator-weaning stage, there was a normal-amplitude compound muscle action potential. Negative inspiratory pressure variation among 14 patients undergoing weaning from mechanical ventilation was observed. Kaplan-Meier survival analysis identified a shorter period of ventilator dependency among patients receiving botulinum antitoxin on day 4 (P=.02). CONCLUSIONS: Patients receiving botulinum antitoxin on day 4 had decreased ventilator dependency. In addition, for patients with foodborne botulism, an effective referral system and team of specialists are needed.

Botulism↗

Sequencing and phylogenetic analysis of neurotoxin gene from an environmental isolate of Clostridium sp.: comparison with other clostridial neurotoxins.

A Clostridium sp. isolated from intestine of decaying fish exhibited 99% sequence identity with C. tetani at 16S rRNA level. It produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E) as well as tetanus antitoxin. The gene fragments for light chain, C-terminal and N-terminal regions of the heavy chain of the toxin were amplified using three reported primer sets for tetanus neurotoxin (TeNT). The neurotoxin gene fragments were cloned in Escherichia coli and sequenced. The sequences obtained exhibited approximately 98, 99 and 98% sequence identity with reported gene sequences of TeNT/LC, TeNT/HC and TeNT/HN, respectively. The phylogenetic interrelationship between the neurotoxin gene of Clostridium sp. with previously reported gene sequences of Clostridium botulinum A to G and C. tetani was examined by analysis of differences in the nucleotide sequences. Six amino acids were substituted at four different positions in the light chain of neurotoxin from the isolate when compared with the reported closest sequence of TeNT. Of these, four were located in the beta15 motif at a solvent inaccessible, buried region of the protein molecule. One of these substitutions were on the solvent accessible surface residue of alpha1 motif, previously shown to have strong sequence conservation. A substitution of two amino acids observed in N-terminal region of heavy chain were buried residues, located in the beta21 and beta37 motifs showing variability in other related sequences. The C-terminal region responsible for binding to receptor was conserved, showing no changes in the amino acid sequence.

Amino Acid Sequence↗

[Identification of strain B 657 of Clostridium botulinum].

Strain 657 has been described as a toxin variant of Clostridium botulinum type B. Toxin neutralization tests performed with types B and A botulinum antitoxins of known potency, avidity and specificity at 20, 200, 2.000 and 20.000 DL50/mouse level of testing have shown that 657 toxin is a mixture of B (90 to 99% of the complex) and A antigenic fractions. The possibility of a cross contamination between A and B serotypes has been, in principle, ruled out through the serologic screening of 33 toxin samples coming one each from 33 well isolated colonies taken from two colony variants of this strain. Strain 657 produces a new complex toxin and is proposed as the candidate for the prototype of a new C. botulinum serotype: subtype Ba.

Animals↗

Immunization of ducks for type C botulism.

A single subcutaneous immunization with a vaccine used for protecting ranch mink (Mustela vison) against type C botulism reduced morbidity and mortality in mallard (Anas platyrhynchos) and northern pintail (Anas acuta) ducks challenged with approximately 4.5 x 10(4) and 2.25 x 10(4) mouse lethal doses (MLD50), respectively, of botulinum toxin at 10 and 15 days post-immunization (pi). There was no significant protection at 5 days pi. Protection persisted in mallards for 90 days pi. To simulate use of vaccine as a part of treatment of sick birds in the field, mallards were exposed to toxin and, when clinical signs were evident, each bird was treated by intraperitoneal injection of type C botulinum antitoxin and one-half of the birds were immunized. Immunization had no significant effect on recovery from intoxication. At 10 days posttreatment, all birds were challenged with toxin. Clinical signs and mortality were significantly less frequent among immunized birds than among non-immunized birds after the second exposure. Immunization might be useful as part of the treatment regimen in botulism outbreaks.

Animals↗

Wound botulism acquired in the Amazonian rain forest of Ecuador.

Wound botulism results from colonization of a contaminated wound by Clostridium botulinum and the anaerobic in situ production of a potent neurotoxin. Between 1943, when wound botulism was first recognized, and 1990, 47 laboratory-confirmed cases, mostly trauma-associated, were reported in the United States. Since 1990, wound botulism associated with injection drug use emerged as the leading cause of wound botulism in the United States; 210 of 217 cases reported to the Centers for Disease Control and Prevention between 1990 and 2002 were associated with drug injection. Despite the worldwide distribution of Clostridium botulinum spores, wound botulism has been reported only twice outside the United States, Europe, and Australia. However, wound botulism may go undiagnosed and untreated in many countries. We report two cases, both with type A toxin, from the Ecuadorian rain forest. Prompt clinical recognition, supportive care, and administration of trivalent equine botulinum antitoxin were life-saving.

Adult↗

Botulism as a cause of respiratory failure in injecting drug users.

BACKGROUND: Wound botulism occurs as a consequence of inoculation of Clostridium botulinum spores into a wound. AIM: To describe such a case of wound botulism. RESULTS: A 23-year-old drug-injecting user presented with bulbar symptoms and progressive signs over a three-day period. The diagnosis of botulism was suspected and was treated with large doses of penicillin and botulinum antitoxin. The diagnosis was confirmed by the presence of serum botulinum toxin A. CONCLUSION: Physicians should be aware of the association of botulism in injecting drug users, particularly in Ireland.

Adult↗