CLOSTRIDIUM BOTULINUM: CHARACTERISTICS, MORPHOLOGY, HABITAT - BIOLOGY - 2025

The Clostridium botulinum is a gram positive bacteria belonging to the genus of Clostridium wide. It is one of the bacteria in this group that has been most studied. It was isolated for the first time by Emile Van Ermengen in the year 1896.

C. botulinum produces a series of toxins that are highly pathogenic for humans. These toxins generate a pathology generically called botulism.

Representation of Clostridium botulinum. Source: By Content Providers: CDC, via Wikimedia Commons

When a case of botulism is diagnosed, it is mandatory to make the report to the competent health authorities, so that they take the necessary measures and thus prevent other people from being infected through the same route.

Likewise, botulinum toxin has been used for some years in the plastic surgery industry, since it is injected in small amounts and by exerting its function on the muscles of facial expression, they make expression lines disappear.

Similarly, it has been used in the treatment of certain pathologies such as blepharospasm and strabismus. Definitely, Clostridium botulinum is a bacteria without half measures, it can be very harmful and toxic or very beneficial for the individual.

Taxonomy

The taxonomic classification of Clostridium botilinum is as follows:

Domain: Bacteria

Division: Firmicutes

Class: Clostridia

Order: Clostridiales

Family: Clostridiaceae

Genus: Clostridium

Species: Clostridium botulinum

Morphology

Clostridium botulinum is a rod-shaped bacterium with rounded edges. It measures 0.5 - 2 microns wide by 1.6 - 2.2 microns long. It does not have a capsule that surrounds it.

Its cell wall is made up of a thick layer of peptidoglycan, as well as teichoic acid and lipoteichoic acid.

Its genetic material is condensed into a circular chromosome. This is one of the largest within the group of gram positive bacteria.

Various studies seem to indicate that the length is due to the fact that it contains a large number of genes that regulate the sporulation process, as well as the synthesis of toxins produced by this bacterium.

In the cultures, colonies of a whitish color, round in shape, with well defined borders are observed.

General characteristics

It is gram positive

This bacterium acquires a violet color when the Gram stain technique is applied. This is because it has a thick layer made up of peptidoglycan. This compound has a particular structure, which retains the pigment molecules.

It is anaerobic

Clostridium botulinum is a strict anaerobic organism. It develops clearly in anaerobic environments (absence of oxygen). Oxygen is toxic to bacteria, so it cannot be in contact with this chemical element.

Produces toxins

The toxins that Clostridium botulinum synthesizes are known as Botulinum toxins. There are a total of eight toxins of this type, which are given by the subtypes of the bacteria, namely: A, B, C1, C2, D, E, F, G, H..

Botulinum toxins A, B and E are those that cause pathologies in humans, while the rest cause diseases in birds, fish and other mammals.

Habitat

Clostridium botulinum is a bacterium that is widely distributed in a wide variety of environments throughout the planet. It has been isolated mainly from the soil and marine sediments. In general, it can be said that it is found in environments with little or no oxygen availability.

Produces spores

The bacteria produce spores that are heat resistant. This means that they can survive extreme temperatures, either very low or very high. These spores diffuse into many environments and in the absence of oxygen they germinate and begin to secrete toxins.

Is pathogenic

Clostridium botulinum spores enter the body and germinate, the bacteria reproducing there and causing tissue damage, mainly in the gastrointestinal tract.

Growing conditions

Among the growth conditions that this bacterium needs, an optimum temperature of 30 ° C and an approximate pH of 7 can be mentioned.

Metabolism

Clostridium botulinum is a bacterium that has a metabolism based on the fermentation of carbohydrates and amino acids. Among the carbohydrates that ferment are glucose and mannose.

Likewise, as fermentation products we can mention: acetic acid, butyric acid, isovaleric acid and propionic acid.

Presents proteolytic and non-proteolytic strains

Within the variety of Clostridium botulinum strains that have been isolated so far, two types have been identified: proteolytic and non-proteolytic.

As their name indicates, proteolytic strains are those that cause protein digestion and also produce H ₂ S. Non-proteolytic ones do not cause protein lysis, they also ferment mannose and have complex nutritional requirements.

It is catalase negative

This bacterium does not have the information in its genome to encode the synthesis of the enzyme catalase. Thanks to this it cannot split the hydrogen peroxide molecule into water and oxygen.

It is indole negative

Clostridium botulinum does not have in its DNA the genes that code for the synthesis of tryptophanase enzymes. Because of this, it is not able to break down the indole group found in the structure of the amino acid tryptophan.

This is another of the biochemical tests that are done for the identification and differentiation of bacteria in the laboratory.

Does not reduce nitrates

This bacterium does not synthesize the enzyme nitrate reductase, so it cannot carry out the chemical reactions that involve the reduction of nitrates to nitrites.

Hydrolyzes gelatin

Thanks to the fact that it synthesizes a group of enzymes known as gelatinases, in cultures it is appreciated that they can cause gelatin to liquefy. A transparent halo can be seen around the colonies, unequivocal evidence that this process has occurred.

Pathogeny

As mentioned above, Clostridium botulinum produces several types of toxins, depending on the subtypes. Of all of them, those that cause some pathology in humans are A, B, E and E.

The spores of this bacterium survive various environmental conditions and germinate when the conditions are right (low oxygen content). Botulinum toxin has been isolated from various foods such as canned foods, some meat products such as hot dogs, and in vegetables such as mushrooms and beets.

The most common way in which the spore enters the body is through ingestion, through the consumption of food that does not comply with the relevant sanitary measures. Another form of entry, but much less common is through a wound or injury.

When the toxin enters the body, it is directed towards the nerve endings, specifically towards the synaptic space. There it enters the neuronal cell Already inside the neuron, it inhibits the secretion of the neurotransmitter acetylcholine, producing flaccid paralysis of the muscle.

Diseases

The disease caused by the bacterium Clostridium botulinum is known as Botulism. It is classified into three types:

• Alimentary botulism: caused by the direct ingestion of the toxins of the bacteria through unhealthy foods.
• Wound botulism: when bacteria enter the body through wounds or lesions on the skin.
• Infant botulism: occurs when young children (under 6 months) ingest spores, which germinate in the gastrointestinal tract and originate bacteria in their vegetative form, which release toxins.

Symptoms

Alimentary botulism

It has an incubation period of approximately 12 to 36 hours. The symptoms that develop are the following:

• Excessive fatigue
• Difficulty mastering the muscles of speech and swallowing
• Blurry vision
• Dry mouth
• Droopy eyelids
• Trouble breathing
• Diarrhea
• Constipation
• Sickness
• Vomiting

Botulism patient. Source: By Herbert L. Fred, MD and Hendrik A. van Dijk (http://cnx.org/content/m14960/latest/), via Wikimedia Commons

Wound botulism

The symptoms of wound botulism are frankly similar to those of alimentary botulism.

• Loss of control of the muscles of speech and swallowing.
• Blurry vision
• Trouble breathing
• Droopy eyelids
• Paralysis

Infant botulism

Incubation period approximately 18 to 36 hours. The most common symptoms it presents are:

• Constipation
• Weak cry
• Drooling
• Droopy eyelids
• Fatigue
• Inability to suck and feed
• Paralysis.

Diagnosis

The procedure used to diagnose this infection is mainly based on laboratory tests and establishment of cultures.

First, the foods that the individual has eaten are analyzed, in order to look for bacteria. Likewise, samples are collected from the patient, both from feces and from blood serum.

Once this is done, cultures can be established to determine if the bacteria are present.

Treatment

Treatment depends on the characteristics of the clinical picture it presents. When the person has ingested the spores that can release toxins in the body, a way is sought to inactivate it. This is achieved thanks to the application of the antitoxin immunoglobulin injection.

Likewise, an attempt is made to control the symptoms with medications intended for this purpose. If the discomforts do not subside, then he is covered to a drastic measure, admitting him to the Intensive Care Unit, where he will be treated with more updated drugs. Finally, the patient must go to rehabilitation to activate the affected muscles.

References

1. Botulism: Symptoms and causes. Retrieved from: mayoclinic.org
2. Botulism. Obtained from: medline. Gov
3. Botulism. Retrieved from: who.int
4. Characteristics of clostridium botulinum and botulinum toxins. Retrieved from: ivami.com
5. Castro, A., Hevia, R., Escobar, M., Rubio J., Mena, O. and Riverón A. (2004). Botulism: clinical and epidemiological aspects and case reports. Surveillance technical report. 8 (5).
6. Clostridium botulinum. Retrieved from: microbewiki.com
7. Shapiro, R., Hatheway, C. and Swerdlow, D. (1998). Botulism in the United States: A Clinical and Epidemiologic Review. Retrieved from: annals.org
8. Sugiyama, H. (1980). Clostridium botulinum neurotoxin. Microbiology Reviews. 44 (3). 419- 448.