Clostridium Botulinum - Microbiology PDF

Clostridium botulinum Introduction Clostridium botulinum is a Gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce the neurotoxin botulinum Size – The size of Clostridium botulinum is about 5 µm × 1.0 µm (micrometer) Spores – The Oval, Sub-te...

Clostridium botulinum Introduction Clostridium botulinum is a Gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce the neurotoxin botulinum Size – The size of Clostridium botulinum is about 5 µm × 1.0 µm (micrometer) Spores – The Oval, Sub-terminal & Bulging spores are present in C. botulinum. Capsule – C. botulinum is a Non-capsulated bacterium  it grows well in the media containing Blood or Serum, commonly Blood Agar medium & Robertson Cooked meat broth medium is used for the cultivation of Clostridium botulinum in Laboratory C. botulinum grows well, produces turbidity and the meat is not digested but may turn Black with foul odor due to the proteolytic action of Clostridium botulinum. It also produces gas and turns the pH of the medium Acidic. Egg Yolk Medium Egg Yolk Agar, Modified is recommended for use as an enriched, non-selective and differential medium used in the cultivation, isolation and differentiation of Clostridium spp. and other anaerobic bacilli Used to test lecithinase and lipase activity C.botulinum is lipase +ve Foods responsible Foodborne botulism occurs when C. botulinum grows and produces toxins in food prior to consumption The botulinum toxin has been found in a variety of foods, including low-acid preserved vegetables, such as green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted and smoked fish; and meat products, such as ham and sausage Toxins by C.botulinum Spores produced by the bacteria Clostridium botulinum are heat-resistant and exist widely in the environment, and in the absence of oxygen they germinate, grow and then excrete toxins. There are 7 distinct forms of botulinum toxin, types A–G. Four of these (types A, B, E and rarely F) cause human botulism. Types C, D and E cause illness in other mammals, birds and fish C. botulinum is widely distributed in soils and in sediments of oceans and lakes. The finding of type E in aquatic environments by many investigators correlates with cases of type E botulism that were traced to contaminated fish or other seafoods Pathophysiology C. botulinum is non-invasive. Its pathogenesis is due to the production of potent neurotoxin 'botulinum toxin' (BT), probably the most toxic substance known to be lethal to humankind. The botulinum neurotoxin is the most potent toxin known till now, with as little as 30- 100 ng potentially fatal All serotypes produce neurotoxin, except C2, which produces an enterotoxin BT is a zinc-dependent protein of 150 kDa (100 kDa heavy chain and a 50 kDa light chain)  Blocking of acetylcholine release is permanent, but the action is short-lasting as the recovery occurs in 2 to 4 months once the new terminal axons sprout Optimum temperature for growth and toxin production of proteolytic strains is close to 35°C Mode of action Within the nervous system, the neurotransmitter is the primary neurotransmitter that sends signals to cells thus contributing to the contraction of the smooth muscle as well as the dilation of blood vessels. By blocking the release of this neurotransmitter, muscle contraction is affected, which results in muscle weakness and paralysis. The toxin may be released by intestinal bacteria spores (C. botulinum) or ingested (canned foods etc).  Infant botulism Infant botulism occurs mostly in infants under 6 months of age. Different from foodborne botulism caused by ingestion of pre-formed toxins in food, it occurs when infants ingest C. botulinum spores, which germinate into bacteria that colonize in the gut and release toxins.spore-contaminated honey has been associated with a number of cases constipation, loss of appetite, weakness, an altered cry and a striking loss of head control Wound botulism Wound botulism is rare and occurs when the spores get into an open wound and are able to reproduce in an anaerobic environment. The symptoms are similar to the foodborne botulism, but may take up to 2 weeks to appear Symptoms The symptoms are not caused by the bacterium itself, but by the toxin produced by the bacterium. Symptoms usually appear within 12 to 36 hours Botulinum toxins are neurotoxic. Foodborne botulism is characterized by descending, flaccid paralysis that can cause respiratory failure. Early symptoms include marked fatigue, weakness and vertigo(loss of balance), usually followed by blurred vision, dry mouth and difficulty in swallowing and speaking. Vomiting, diarrhoea, constipation and abdominal swelling may also occur. can progress to weakness in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected symptoms  The manifestations of botulism are due to a decrease in the availability of acetylcholine in the cranial nerve and parasympathetic nerve terminals. Common symptoms include: Diplopia(double vision), dysphasia(diff: in swallowing), dysarthria(slurred or slow speech) Descending symmetric flaccid paralysis of voluntary muscles Loss of deep tendon reflexes Constipation Respiratory muscle paralysis may lead to respiratory failure and death. Botox The bacterium C. botulinum is the same bacterium that is used to produce Botox, a pharmaceutical product predominantly injected for clinical and cosmetic use. Botox treatments employ the purified and heavily diluted botulinum neurotoxin type A used therapeutically for the treatment of spasmodic conditions such as strabismus, blepharospasm(abnormal contraction of the eyelid muscles), and myoclonus Diagnosis Diagnosis is usually based on clinical history and clinical examination followed by laboratory confirmation including demonstrating the presence of botulinum toxin in serum, stool or food, or a culture of C. botulinum from stool, wound or food Treatment Antitoxin should be administered as soon as possible after a clinical diagnosis. Early administration is effective in reducing mortality rates. Severe botulism cases require supportive treatment, especially mechanical ventilation, which may be required for weeks or even months Prevention C. botulinum will not grow in acidic conditions (pH less than 4.6), and therefore the toxin will not be formed in acidic foods (however, a low pH will not degrade any pre-formed toxin). Combinations of low storage temperature and salt contents and/or pH are also used to prevent the growth of the bacteria or the formation of the toxin. Good practice in food preparation particularly during heating/sterilization and hygiene WHO keys The WHO Five Keys to Safer Food serve as the basis for educational programmes to train food handlers and educate the consumers. They are especially important in preventing food poisoning. The Five Keys are: keep clean separate raw and cooked cook thoroughly keep food at safe temperatures use safe water and raw materials.