Clostridium botulinum: Description, Causes and Risk Factors:A bacterial species that occurs widely in nature and is a frequent cause of food poisoning (botulism) from preserved meats, fruits, or vegetables that have not been properly sterilized before canning. The main types, A to G, are characterized by antigenically distinct, but pharmacologically similar, very potent neurotoxins, each of which can be neutralized only by the specific antitoxin; group C toxin contains at least two components; the recorded cases of human botulism have been due mainly to types A, B, E, and F; infant botulism occurs when colonization of the gastrointestinal tract with Clostridium botulinum results in absorption of the toxin through the gastrointestinal wall; type C) causes botulism in domestic and wild water fowl; C* and D are associated with intoxications in cattle. Type E is usually associated with improperly processed fish products.
Clostridium botulinum is a Gram-positive, rod-shaped bacterium that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, that cause the flaccid muscular paralysis seen in botulism. They are also the main paralytic agent in BotoxTM. C. botulinum is an anaerobic spore-former, which produces oval, subterminal endospores and is commonly found in soil.
The current nomenclature for Clostridium botulinum recognizes four physiological groups (I-IV). The classification is based on the ability of the organism to digest complex proteins. Studies at the DNA and rRNA level support the subdivision of the species into groups I-IV. Most outbreaks of human botulism are caused by group I (proteolytic) or II (non-proteolytic) C. botulinum. Group III organisms mainly cause diseases in animals. There has been no record of Group IV C. botulinum causing human or animal disease.
Although the seven neurotoxins (A, B, C, D, E, F and G) are genetically distinct, they possess similar molecular weights and have a common subunit structure. The complete amino acid sequences of the various serotypes are becoming known. Regions of sequence homology among the serotypes and between botulinum toxins and tetanus toxin, suggest that they all employ similar mechanisms of action. The toxins are synthesized as single chain polypeptides with a molecular mass of approximately 150 kDa. In this form, the toxin molecules have relatively little potency as neuromuscular agents. Neurotoxin activation requires a two-step modification in the tertiary structure of the protein.
While Clostridium botulinum is unique in that it grows in an oxygen-free environment, it is the same as other food-borne pathogens in other respects, which is to say, proper refrigeration will slow the growth of the bacteria, and cooking will kill it. Note, however, that the botulism toxin (as opposed to the bacteria that produces it) needs to be boiled for at least 20 minutes to destroy it. An acidic environment will also prevent the growth of Clostridium botulinum. When making stews and thick soups, you should cool the leftovers quickly and then refrigerate right away. And to be extra safe, avoid eating home-canned foods, homemade garlic in oil and that sort of thing.
Initial symptomscan include nausea, vomiting, abdominal cramps or diarrhea. After the onset of neurologicsymptoms, constipation is typical. Dry mouth, blurred vision, and diplopia are usually the earliestneurologic symptoms. They are followed by dysphonia, dysarthria, dysphagia, and peripheralmuscle weakness. Symmetric descending paralysis is characteristic of botulism.
The history and physical examination is usually the first step in diagnosing Clostridium botulinum. However, nerve conduction studies (EMG), spinal fluid examinations and brain scans are helpful. Botulinum bacteria can be isolated from the stool of infected people in the foodborne and infant variety of the disease.
Foodborne botulism - If diagnosed early, antitoxin should be administered to block the actions of the exotoxin. If respiratory failure has set in, mechanical ventilator and intensive care is required. Infant botulism - Remove the contaminated food by inducing vomiting and enemas. Good supportive care is further required for recovery.
Wound botulism - Administration of antitoxins to neutralize the exotoxin, surgical debridement and excision of the effected area, followed by the required supportive treatment.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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