Clostridium tetani characteristics, morphology, habitat

Basil Manning

Clostridium tetani It is a gram-positive bacteria well known to be the causative agent of tetanus disease. The first who managed to isolate the bacteria in a culture was the Japanese doctor and bacteriologist Kitasato Shibasaburo.

Later it was established that this bacterium exerted its effect through an extremely powerful neurotoxin that directly attacks the nerve terminals of neurons.

Clostridium tetani seen under the microscope. Source: By Content Providers (s): CDC [Public domain], via Wikimedia Commons

Later, tetanus toxoid could be developed, which is used as a vaccine, since it provides the inoculated individual with active immunity against the bacteria..

The Clostridium tetani It is a bacterium that lives mainly in the soil and in places with poor hygiene, so it is vitally important to take the pertinent care measures so as not to run the risk that the bacteria may enter the bloodstream.

Tetanus has been a known disease since ancient times. It is even believed that it was the doctor Hippocrates who described the first symptoms of this pathology. Throughout history, a large number of cases of this disease have been evidenced, with its characteristic symptom: spasms and muscle stiffness..

Currently, the tetanus vaccine is part of the vaccination schedule for all infants. With this, what is sought is to reduce the prevalence and incidence of tetanus. Fortunately, little by little the disease has been controlled and its frequency is not as high as it was some 30 years ago.

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
  • 4 Pathogenesis
  • 5 Risk factors
  • 6 Symptoms
  • 7 Diagnosis
  • 8 Treatment
  • 9 References


The taxonomic classification of the Clostridium tetani is the next:

Domain: Bacterium

Division: Firmicutes

Class: Clostridia

Order: Clostridial

Family: Clostridiaceae

Gender: Clostridium

Species: Clostridium tetani


The Clostridium tetani It is a bacterium that has a thin, bacillus shape, measuring 0.3-2 microns wide by 1.5-2 microns long. During their maturation process they produce a terminally located spore, larger than the bacillus, which gives it its characteristic “drumstick” appearance..

It is surrounded by a cell wall that contains a thick layer composed of peptidoglycan, as well as an inner membrane. On the cell surface they present peritric flagella, which contribute to give it mobility, although some strains are immobile.

In the cultures, small colonies are seen, with a weak halo of hemolysis around them. They are greyish in color, translucent, and have irregular edges.

General characteristics

It is Gram Positive

The Clostridium tetani It is a bacterium that is within the group of gram positive ones. This is thanks to the thick layer of peptidogyne, a compound that traps dye molecules and retains them. Due to this, the bacterial cells acquire the characteristic violet color of this type of bacteria..

Form endospores

The spores produced by the Clostridium tetani They grow at the terminal end of the bacteria and their diameter exceeds the width of the bacteria. These spores are highly resistant to heat. These can remain in the soil, in a dormant state for approximately 40 years, preserving their infectious capacity..

It is strict anaerobic

This bacterium does not require oxygen for any of its metabolic processes, since it can use other types of elements or compounds. This element is toxic to bacteria. It develops only in the total absence of this chemical element.

Growing conditions

Among the requirements that this bacterium has to develop and grow is an average temperature of 37 ° C, as well as an approximate pH level of between 7 and 7.5. In addition to this, you need a large amount of amino acids and vitamins..

Produces an exotoxin

The Clostridium tetani produces a neurotoxin known as tetanospamine. This toxin is a peptide that acts at the level of the main cells of the nervous system, the neurons, preventing the release of some neurotransmitters.

It also produces another toxin, tetanolysin. This toxin is still being studied, since its effect on the host has not yet been elucidated. It is inhibited by serum cholesterol and oxygen.

Is pathogenic

This bacterium is a recognized pathogen, responsible for causing tetanus in humans. This is a disease that causes a series of muscle spasms and violent contractions, in addition to stiffness..

The bacterium infects the organism through the entry of spores into it. Inside, spores germinate and begin to wreak havoc on the autonomic nervous system..


The bacterium, both in its vegetative and spore form, is found mainly in warm and humid areas, as well as in the gastrointestinal tract and in the feces of various animals such as horses, sheep, and dogs. This bacteria is usually found in dirty places.


The Clostridium tetani cannot ferment carbohydrates. On the contrary, if you can carry out the fermentation process of several amino acids, namely: aspartate, glutamate, histidine and phenylalanine.

It is indole positive

The Clostridium tetani synthesizes a group of enzymes known as tryptophanases. These enzymes act on the amino acid tryptophan and break the indole group that is part of its structure. This is why the Clostridium tetani it is classified as indole positive. This serves to differentiate it from other bacteria..

It is catalase negative

This bacterium does not synthesize the catalase enzyme, which is why it cannot cause the breakdown of the hydrogen peroxide (H2O2) molecule in water and oxygen. This is an important characteristic that at the laboratory level serves to identify and differentiate bacteria..

Hydrolyzes gelatin

The bacterium is capable of synthesizing enzymes known as gelatinases. This group of enzymes causes gelatin to liquefy. When this bacterium is in a culture, a transparent halo is seen around it. This is an unequivocal sign that gelatin hydrolysis has occurred..


This is a bacterium that has a reservoir and hosts. In the first case, the human being together with other mammals are its reservoirs. While the hosts are: humans, equines, birds, cats, primates and rodents, among others.

The spores of the bacteria enter the body through an open wound or injury. Inside the body, in dead cells, it achieves the anaerobic environment that its spores need to germinate.

When the spores germinate, they begin to synthesize and release tetanospamine, which is its toxin known as responsible for the development of tetanus..

The neurotoxin secreted by the Clostridium tetani reaches the spinal cord where it exerts its action. Here, the toxin intervenes in the synaptic space of neurons, preventing the release of neurotransmitters. This causes the muscles to spasm very painful and intense..

Risk factor's

Risk factors are those characteristics, customs or situations that increase the chances of suffering from any pathology. In the case of clostridium tetani, your risk factors are as follows:

  • Not having the complete vaccination schedule with its respective reinforcements.
  • Some deep injury that is not cleaned properly
  • IV drug use
  • Infected foot ulcers
  • Surgical wounds
  • Dental infections


Among the most characteristic and obvious symptoms of tetanus we can mention:

  • Excessive sweating
  • Increased salivary secretion
  • High fever
  • Difficulty swallowing (swallowing)
  • Stiffness and certain spasms in various muscles, especially those of the jaw.
  • Stiff neck muscles
  • Tachycardia
  • High blood pressure
  • Stiffness of the abdominal muscles.
  • Irritability
  • Inability to control the anal and urethral sphincters
Neonatal patient with tetanus. Source: By Photo Credit: Content Providers (s): CDC [Public domain], via Wikimedia Commons


The diagnosis of this pathology is practically consolidated in the observation of the clinical picture by the doctor. Likewise, he must delve into the patient's history: having received the boosters of the toxoid vaccine and his age are important elements to take into consideration..

Trying to grow the bacteria from samples taken from the lesion is practically useless, since conclusive results are not obtained. Generally, an expert doctor, by visualizing the signs and making a correct interrogation, can reach the diagnosis of the pathology without room for mistakes..

This is important, since the sooner tetanus is diagnosed, the faster measures can be taken and the patient will have a better chance of survival..


There is no specific treatment for tetanus as such. However, there are a series of cautions and recommendations that should be followed when a possible infection is suspected. Among these are:

  • Wound care: A deep and systematic washing of the wound must be carried out, with plenty of clean water and the remains of dead tissue must be removed, making the blood reach the site, providing oxygen. In this way, the favorable environment for the proliferation of the bacteria is avoided..
  • Medication supply: Among the drugs that the doctor can select to give the patient are: antibiotics, tetanus antitoxin, the vaccine and some sedatives. Of course, this will depend on the criteria of the doctor and the characteristics of each particular case..
  • Seclusion in the Intensive Care Unit: Due to the lethal effects of this pathology on the body, the patient may need intensive care hospitalization. This is done to address potentially fatal consequences, such as respiratory muscle involvement..


  1. Low GC content and Gram Positive bacteria. Obtained from: micro.
  2. Clostridium tetani. Obtained from: microbewiki
  3. Clostridium tetani. National Institute of Safety and Hygiene at Work. Obtained from:
  4. Montecucco, C. and Schiavo, G. (1994) Mechanism of action of tetanus and botulinum neurotoxins. Molecular Microbiology. 13. 1-8
  5. Ríos, M., García, Al., Alves, E., Brea, R. and Núñez, J. (2016). Infection by Clostridium tetani: suspect it to diagnose it. Clinical Galicia. 77 (4). 175-176
  6. Smietanska, K., Chudziak, R. and Rastawicki, W. (2013). [Characteristics of Clostridium tetani and laboratory diagnosis of tetanus. Med Dows Mikrobiol. 65 (4). 285-295
  7. Tetanus. Retrieved from:

Yet No Comments