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Bacteria play an important role for life on earth. Most of them are involved in recycling nutrients. Humans use them in a variety of applications; to prepare foods (yogurt, cheese etc), to produce antibiotics, to clean waste water etc. Nevertheless, there are some of them which are pathogenic to humans. One of them, Clostridium botulinum, is the most important bacterium for the canning industry.
Clostridium botulinum is an anaerobic, spore-forming, rod-shaped bacterium, which can grow and yield a lethal toxin in food. According to Gram’s stain, it is determined as a gram-positive bacterium. Gram’s stain is a differential staining method of discriminating bacterial species into two large groups (Gram-positive and Gram-negative) based on the chemical and physical properties of their cell walls (Ward 2007). Clostridium botulinum organisms are usually detected in soils and marine sediments universally. Therefore, it may contaminate vegetables cultivated in or on the soil. It is also located in the gastrointestinal (GI) tract of fishes, birds and mammals (Nantel 2002).
Human botulism is mainly caused by Clostridium botulinum spores that produce toxin types A, B, E and F. Type A and B toxins are caused by the consumption of home-canned foods (vegetable, fruits and meat products). Type E toxin is attributed to marine products, whereas type F toxin was found in homemade venison jerky (Botulism in the United States 1998).
Smith (cited in Erbguth 2009) reported in his dissertation on botulism an alimentary proclamation announced in the tenth century by Emperor Leo VI of Byzantium (886–911), in which production of blood sausages was prohibited. This edict may have arisen by some affairs associated with cases of food poisoning. In a similar way, Erbguth (2009) describes shamans providing to Indian maharajas a flavorless powder extracted from blood sausages dehydrated under anaero-bic conditions. This fatal dose of botulinum toxin would be added to the enemies’ meal at an invited banquet. In the late 1700s, botulism led to many deaths in Europe, especially Germany. Grüsser (cited in Erbguth 2009) describes that the economic poverty caused by the Napoleonic War (1795–1813) led to the neglect of sanitary measures in rural food production. The primary origin of botulism was smoked blood sausages. By 1811, the Department of Internal Affairs of the Kingdom of Württemberg accredited “sausage poisoning” to a substance named “prussic acid”.
In addition, Dr. Kerner correctly specified all the neurological symptoms of botulism recognized nowadays.
“Botulism” derives from the Latin word “botulus”, meaning sausage. This term arose originally in Müller’s reports, an author in nineteenth century (Torrens cited in Erbguth 2009). Finally, Emile van Ermengem, a microbiologist, after isolating this bacterium, he denominated it Bacillus botulinus, which was renamed Clostridium botulinum in later years (Erbguth 2009).
Nevertheless, due to their extreme toxicity, Clostridium botulinum neurotoxins were one of the first agents to be assayed as a biological weapons agent by many countries, such as Japan, Germany, the United States, Russia, and Iraq. Dembek (n.d.) remarks that by the 1930s, in occupied Manchuria, Japan formed a biological warfare command addressed as Unit 731. As confirmed by the military medical commander of Unit 731, lethal doses of C. botulinum were given to prisoners (Figure 3: shows Japanese scientists testing the lethality of various disease agents). Botulinum toxin was referred to as agent X (Dembek et al n.d.).
Turning to the Clostridium botulinum characteristics, although botulinum spores are rather heat resistant, the toxin itself is heat sensitive. Heating food at 80 oC for 30 minutes or 100 oC for 10 minutes destroys the active toxin. The thermal resistance of spores escalates in foods pH and a with a higher lower salt content. C. botulinum favors living among weaker and minor microorganisms. Thus, by the time an acidifying agent is added, e.g. in pickling, other bacteria will grow and prevent the growth of C. botulinum. The toxin is also deactivated (Saulo 2007).
Foodborne botulism is divided in two physiologically and genetically clostridia, proteolytic C. botulinum and non-proteolytic C. botulinum. Moreover, toxins induced by some Clostridium botulinum bacteria are non-proteolytic, which means that affected food may look and smell normal. Proteolysis generally produces unpleasant odors during growth. Oxford dictionaries (2012) define proteolysis as the breakdown of proteins or peptides into amino acids by the action of enzymes. On the contrary, the non-proteolytic nature means that foods may seem unaltered with no unpleasant accompanying odor. Additionally, Proteolytic C. botulinum is a mesophile. Wikipedia (2011) describes mesophile as an organism that grows best in a moderate temperature). It has a minimum augmentation temperature of 10 °C-12 °C, and creates toxins of types A, B and F. Non-proteolytic C. botulinum is psychrotrophic. Psychrotrophic nature indicates bacteria that are capable of surviving or even thriving in a cold environment (Wikipedia 2011). It is able to grow and create toxin at 3.0 °C and produces toxins of types B, E and F. Hence, non-proteolytic C. botulinum is a serious matter in chilled foods, as seen in table 1 (Peck et al 2006).
The symptoms detected in foodborne botulism, are primarily gastrointestinal. These include nausea, vomiting, abdominal cramps and, occasionally, diarrhea. At a later stage, the prevailing symptoms are neurological. Such as diplopia (blurred or double vision), dry mouth, slurred speaking, fatigue and muscle weakness. If the infection is severe, respiratory muscles are affected, resulting in ventilatory dysfunction and death if help is not provided. The time between toxin consumption and the symptoms outbreak varies from 18 to 36 hours (Botulism in the United States 1998).The growth of C. botulinum is prevented by high temperature, acidification, dehydration, salination, as well as with certain food preservatives e.g. nitrite, ascorbates, polyphosphates etc. Generally, food packaging should be always inspected for any type of damage like punctures and tears. Swollen, gassy cans or anything spoiled must be avoided, as well as discolored, moldy products that have bad odor.
In conclusion, C. botulinum is the bacterium that causes a lethal paralytic disease, botulism. Botulism is one of the most dangerous forms of food poisoning as the illness can be fatal in three to 10 days if nottreated. Subsequently, prevention is of the utmost importance.
One of several incidents of food poisoning caused by Clostridium botulinum toxin A arose in Fukuoka prefecture, Japan. The majority of the patients had consumed commercial fried lotus rhizome solid mustard with no heating. C. botulinum toxin type A has the highest deadly function. Hence, eleven of the 36 persons addressed as patients died of botulism. Most of the patients and the deceased were considered to have ingested the food without heating it, due to the fact that no symptoms were discerned among persons who ate the food after heating (Otofuji et al 1987).
On top of this, the most recent incidents of human botulism occurred on July 2007, in USA, involving a commercially canned chili sauce (CDC 2007).
Furthermore, C. botulinum (toxin types A, B, E, and C, D) may also exist in bio-bin waste. Böhnel (2002) remarked that fly larvae out of bio-bins may be vectors of the likely fatal C. botulinum.
Another form of Clostridium botulinum is infant botulism. Unlike foodborne botulism, infant botulism is a contagious disease concerning only infants younger than one year. Due to the underdeveloped intestinal micro flora, the spores carried into the intestines may grow and induce active toxin. For this reason, honey should not be given to infants. The contamination of honey by spores of C. botulinum potentially takes place either in the beehive or by the time of the extraction phase. Either way, the contagion is considered to occur via dust. Nevertheless, most infant patients inhale C. botulinum spores carried by dust that sticks to saliva and is swallowed. Such cases are not considered preventable (Nevas 2006). In 1976, Dr. Stephen S. Arnon of the California Department of Health Services detected 30 to 40 cases of infant botulism yearly. Canada, Massachusetts and Argentina begun to report cases some years later (Emmeluth 2010).
However, Clostridium botulinum is also used in beauty cosmetics. Botulinum toxin (Botox) type A is a bacterial toxin that prevents nerves from functioning normally (a neurotoxin). It inhibits nerves from releasing a chemical called acetylcholine, which is vital for the nerves to communicate with muscle cells. Thus, it prevents muscles from receiving nerve stimulation. Preventing nerve stimulation of muscles causes the muscles to become paralyzed. It is useful for treating conditions where excessive nerve stimulation to muscles is causing abnormal muscle functioning, contractions or spasms. It is injected into the affected muscle for this purpose. In addition, it is used to improve the appearance of frown lines between the eyebrows and wrinkles (European medicines agency 2003). Drs. Alan Scott and Edward Schantz was a pioneer in using Clostridium botulinum to treat human disease in 1968 such as blepharospasm and strabismus. Jean Carruthers, a Canadian ophthalmologist in 1987, noticed that wrinkles vanished after using botulinum toxin A for blepharospasm. Along with her husband, Alastair Carruthers, a dermatologist, changed the field of cosmetic once and for all (Ting & Freiman 2004).
Clostridium botulinum, started as a food poison, continued as a biological weapon, and it ends as one of the most essential pharmaceutical in ophthalmology, neurology and dermatology.
I would like to thank my supervisor, Dr. Tryfon Adamidis, for his patient guidance, encouragement, advice and thoughtful insight he has provided throughout my time as his student. I am extremely lucky to have a supervisor who cares so much about my work, and who responds to my questions and queries so promptly.