BoNTs cleave SNARE proteins and prevent Ach release
Clinical Perspective of Clostridium botulinum
There are four types of botulism, characterized by the method of delivery of the toxin.
The toxin cannot pass through the skin, thus, transmission requires a break in the skin or direct absorption through mucus membranes in the lungs or GI tract.
Foodborne botulism is the result of the ingestion of food contaminated with Clostridium botulinum containing the preformed toxin. Note: Ingestion of the toxin makes a person ill, not Clostridium botulinum itself.
Wound botulism occurs when a break in the skin becomes infected with Clostridium botulinum which then multiply and release botulism toxin into the blood.
Inhalation botulism occurs when aerosolized botulism toxin enters the lungs.
Infant botulism is the result of the infestation of the digestive tract with Clostridium botulinum.
In infant botulism, illness results from infestation of the GI tract with Clostridium botulinum. Such infestation is generally not an issue in individuals older than one year due largely to the large number of competing microorganisms found in the mature GI tract.
Roughly 100 cases of botulism are reported in the U.S. each year.
Approximately 25% are foodborne, 72% are infant botulism, and the remaining 3% are wound botulism.
Inhalation cases do not occur naturally.
Wound botulism is on the rise due to an increase in the use of black tar heroin. The source of the botulism could be the drug itself, a cut in the drug, dirty injection equipment, or contamination during the preparation process.
The incubation period varies according to the mode of transmission, rate of absorption of the toxin, and the total amount and type of toxin.
Foodborne botulism usually takes 24-36 hours to manifest itself.
Wound botulism often takes 3 or more days to appear.
Inhalation botulism has occurred very rarely, but incubation times may range from several hours to perhaps days, again depending upon the type and amount of toxin inhaled.
All four types of botulism result in symmetric descending flaccid paralysis of motor and autonomic nerves always beginning with the cranial nerves. These symptoms are preceded by constipation in cases of infant botulism.
If left untreated symptoms may expand to include paralysis of respiratory muscles as well as the arms and legs.
Asphyxiation due to respiratory paralysis is the most common cause of death in botulism cases.
Botulism results in death in approximately 8% of documented cases. The key to survival is early diagnosis. For the period 1899-1949 the case fatality ratio was approximately 60%. For the Period 1950-1996 the case-fatality ratio was 15.5%.
This improvement is largely attributable to improvements in respiratory intensive care and availability and prompt administration of the antitoxin.
Antitoxin can halt the progress of symptoms if administered early to victims of food and wound botulism.
Antitoxin is not given to victims of infant botulism because when this is diagnosed it is generally too late for the antitoxin to do any good.
Wound botulism is treated surgically to remove the Clostridium colony.
Artificial respiration is required if paralysis reaches the lungs. Such respiratory assistance may be required for weeks to months.
The paralysis induced by the toxin slowly improves over the course of many weeks.
Many patients make close to a full recovery following weeks to months of intensive care, however, lingering effects such as fatigue and shortness of breath may linger for years.
Attempts to develop an effective botulism vaccine date back to the 1940’s. One current effort (now moving into clinical trials) uses injection of a non-toxic carboxy-terminus segment of the botulism toxin to confer immunity to the toxin.
The symptoms of botulism are similar to those of Guillain-Barré syndrome, stroke, and myasthenia gravis.
As a result, botulism is probably substantially under-diagnosed.
Serum electrolytes, renal and liver function tests, complete blood tests, urinalysis, and electrocardiograms will all be normal unless secondary complications occur.
A brain scan, spinal fluid examination, electromyograph, or tensilon test may be required to positively identify botulism.
The most effective test comes from the identification of botulism toxin in serum or stool. The test is most often carried out by injecting samples into a mouse and observing whether symptoms of botulism develop.
However, the false negative rate for this test can be as high is 60% for serum samples and near 80% for stool samples in individuals clinically diagnosed with botulism.
Collection of samples early in the progression of the illness may be helpful, however, large outbreaks have occurred in which none or a very low percentage of victims produced a positive test result.
In vitro methods utilizing ELISA are under development but are not yet validated.
Isolation of Clostridium botulinum from the patient’s feces or gastric sample is a good confirmation of botulism as the organism is rarely found in humans in the absence of the botulism poisoning, however, poisoning can occur without ingestion of the microorganism at all.
If botulism poisoning is suspected clinicians are advised to contact local and state health authorities who should then contact the CDC
Proper food preparation is one of the most effective ways to limit the risk of exposure to botulism toxin.
Boiling food or water for ten minutes can eliminate some strains of Clostridium botulinum as well as neutralize the toxin as well. However, this will not assure 100% elimination.
Limiting growth of Clostridium botulinum and the production of botulism toxin is an alternative to their outright destruction.
Temperature, pH, food preservatives, and competing microorganisms are among the factors that influence the rate and degree of Clostridium botulinum growth.
Growth of most strains of Clostridium botulinum will not occur below 10 or above 50 degrees Celsius.
Clostridium botulinum will not grow in media with pH values lower than about 5.
Food preservatives such as nitrite, sorbic acid, parabens, phenolic antioxidants, polyphosphates, and ascorbates inhibit the growth of the microorganism.
Lactic acid bacteria including Lactobacillus, Pediococcus, and Pactococcus can inhibit the growth of Clostridium botulinum by increasing the acidity of the medium.
While the cause of roughly 85% of infant botulism cases is unknown, in up to 15% of infant botulism cases the causes was ingestion of honey. Infants younger than one year old should not be fed honey.
Avoid home-processed foods if at all possible, especially those with a low salt and acid content.
Botulism toxin is destroyed at a temperature of 176 F, thus if you must eat home-processed foods, boil them for 10 minutes before eating if at all possible.
If canning vegetables, use a pressure cooker, as it will kill any spores because it can reach temperatures above boiling.
Weaponization of Botulinum Toxin
What does it mean to “weaponize” a biological agent?
The "weaponization" of a microbial pathogen or toxin involves:
rendering the agent resistant to standard antibiotic drugs
freeze-drying and milling the agent into an extremely fine powder, consisting of particles tiny enough to become readily airborne and inhaled into the victims' lungs to cause infection
stabilizing the agent so that it will remain infectious for a longer period after release
treating the powder with chemical additives that absorb moisture and reduce clumping, so as to facilitate aerosolization.
Answer provided by Jonathan B. Tucker, Ph.D.
an expert on chemical and biological weapons in the Washington, D.C and a biological weapons inspector in Iraq under the auspices of the United Nations Special Commission in 1995