Clostridium Tetani: Characteristics, Morphology, Habitat

Clostridium tetani is a gram-positive bacterium well known to be the causative agent of tetanus disease. The first to isolate the bacteria in 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.

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

The Clostridium tetani is a bacterium that lives mainly on the ground and in places with poor hygiene, so it is vital to take appropriate measures careful not to run the risk that the bacteria can 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.


The taxonomic classification of Clostridium tetani is as follows:

Domain: Bacteria

Division: Firmicutes

Class: Clostridia

Order: Clostridiales

Family: Clostridiaceae

Genus: Clostridium

Species: Clostridium tetani


The Clostridium tetani is a bacterium having a rod – shaped, thin, measuring 0.3 to 2 microns wide by 1.5 to 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 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 is a bacterium found in the group of gram positive. This is thanks to the thick layer of peptidogiene, a compound that traps dye molecules and holds them. Due to this, the bacterial cells acquire the characteristic violet color of this type of bacteria.

Form endospores

The spores produced by Clostridium tetani 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 latent state for approximately 40 years, conserving 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 tetanoespamina. 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, the 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 generally found in dirty places.


The Clostridium tetani can not 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 triptofanasas. These enzymes act on the amino acid tryptophan and break the indole group that is part of its structure. This is why Clostridium tetani 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, felines, primates and rodents, among others.

The spores of the bacteria enter the body through an open wound or injury. Inside the organism, 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 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 the following:

  • Not having the complete vaccination schedule with its respective reinforcements.
  • Some deep injury that is not cleaned properly
  • Intravenous 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


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 a diagnosis of the pathology without any mistakes.

This is important, as the sooner tetanus is diagnosed, the quicker measures can be taken and the better chance of survival for the patient.


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 : the wound must be thoroughly and systematically washed, with plenty of clean water and the remains of dead tissue 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 medications that the doctor can select to administer to 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 hospitalization in intensive care. This is done to address potentially fatal consequences, such as respiratory muscle involvement.


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