Clostridium

Generality

Clostridium is the name of a genus of Gram-positive bacteria with particular characteristics, including the obligatory anaerobiosis, the existence in nature both in the vegetative state and in the form of spores, the great diffusion in the environment and the rod-shaped form.

What is a Clostridium ?

Clostriudium is the name of a genus of Gram-positive, obligate, sporogenic, anaerobic bacteria, similar in shape to a rod (rod-shaped form).

Clostridium are obligate anaerobes: what does it mean?

A bacterium is called an anaerobic, when

• Its growth and replication capacities occur only in the absence of molecular oxygen;
• The presence of molecular oxygen represents a threat to its survival.

For the bacteria of the genus Clostridium, the absence of molecular oxygen represents the condition that allows and justifies the assumption of the so-called vegetative state .

In microbiology, by a vegetative state of a bacterium, we mean the active state of a bacterium, the one in which it is able to grow and replicate.

As we will see later, other important functions of Clostridium bacteria also depend on the absence / presence of molecular oxygen.

In the microbiological field, the life condition of those organisms, whose existence does not depend on the presence of molecular oxygen or is impossible in the presence of molecular oxygen, takes the name of anaerobiosis

Clostridium are sporogenic: what does it mean?

A bacterium is called sporogenous, when it can turn into spores or give rise to spores .

For the bacteria of the genus Clostridium, the spore typically represents a non-replicative quiescent life form, alternative to the so-called vegetative state, assumed to survive for a long time in any condition, even the most adverse; the spores of Clostridium, in fact, are very resistant and can defend themselves very well from intense heat, lower temperatures, more powerful antiseptics as well as from the condition that makes the life of Clostridium themselves in a vegetative state impossible: the presence of oxygen.

The most emblematic example of what has just been stated is Clostridium tetani, one of the many species of Clostridium existing in nature, famous as it is the etiological agent of tetanus.

Microbiological note

In microbiology, the passage of a bacterium from the vegetative to the spore state is called sporogenesis, while the opposite transformation - from spora to microorganism in a vegetative state - is known as germination .

Origin of the name

The word " Clostridium " comes from the Greek word " kloster " ( κλωστήρ ), which means "spindle" or "spindle".

The use of a word with this etymological origin is linked, as it is easy to understand, to the typical fusiform aspect of the bacteria belonging to the Clostridium genus.

Features

There has already been extensive talk of forced anaerobiosis, sporadic capacity and rod-like form.

Here, therefore, the remaining most important characteristics of a typical Clostridium will be discussed: dimensions, shape of spores, movement, habitats and toxic capacities.

dimensions

In nature, there are Clostridium whose length can range from 0.3 to 2 micrometres and Clostridium whose length can vary between 1.5 and 20 micrometers.

Therefore, as regards the size of the Clostridium, there is considerable variability.

Spore form

The spores of bacteria of the genus Clostridium possess a characteristic bottle shape.

Movement

The bacteria of the genus Clostridium are endowed with a certain motility, deriving from a series of flagella spread a little on all their surface.

In microbiology, bacteria with such a distribution of flagella are called peritrichous bacteria .

Habitat

As a rule, bacteria of the genus Clostridium are ubiquitous ; after all, they can be found almost everywhere:

• In the ground;
• In the dust;
• In waste water;
• In marine sediments;
• In the intestinal tract of herbivorous animals (eg: horses, cattle and goats) and in that of other animals such as dogs, cats, chickens, etc .;
• In the faeces of the aforementioned animals and in the manure that can be produced;
• In the intestinal tract of the human being;
• Etc.

Pathogenic abilities: toxins

In a vegetative state, some bacteria of the genus Clostridium are able to produce substances with pathogenic effects on human beings.

Generally protein-based, these substances are called toxins .

A Clostridium is not a Bacillus

Many people confuse the bacteria of the genus Clostridium with the bacteria of the genus Bacillus (the so-called bacilli ), probably because both these genera belong to the same phylum as the Firmicutes .

Given the significant differences between a Clostridium and a Bacillus, confusing these two bacterial genera is decidedly serious.

In the box below, the article reports the aforementioned differences.

Species

According to the latest microbiological studies, there are more than 100 species of bacteria belonging to the genus Clostridium in nature .

Among all these species of Clostridium, the most important, also considering the pathogenic effects they can have on humans, are:

• Clostridium botulinum
• Clostridium difficile
• Clostridium perfringens
• Clostridium tetani
• Clostridium sordellii

Other Clostridium species:

• Clostridium thermocellum

• Clostridium acetobutylicum

• Clostridium butyricum

• Clostridium histolyticum

• Clostridium ljungdahlii

• Clostridium beijerinckii

• Clostridium diolis

Clostridium botulinum

Clostridium botulinum is the responsible bacterial agent in humans, through 4 of its 7 toxins, of a very dangerous and potentially deadly infection, whose name is botulism .

Botulism first causes symptoms such as diarrhea, severe abdominal pain, nausea and vomiting; then, at a later time, it causes far more serious disorders, such as visual changes, dry mouth and episodes of flaccid paralysis with severe repercussions on swallowing, phonation, chewing and breathing.

Among the botulism patients, the main cause of death is asphyxia due to the repercussions that flaccid paralysis has on respiratory capacity.

THE TOXINS OF CLOSTRIDIUM BOTULINUM

Also known as botulinum toxins, Clostridium botulinum toxins responsible for botulism in human beings are among the best known examples of neurotoxins, or toxins that, due to a tropism towards the nervous system, are able to enter neurons, reach important structures such as the brain and spinal cord, and, finally, alter the functions of these structures.

ROUTES OF CONTAGIOUS

Clostridium botulinum can infect humans and produce botulism in at least three different ways:

• Through the ingestion of food contaminated by its neurotoxins;
• Through skin wounds following the penetration of foreign bodies, such as nails, splinters or spines, contaminated by its spores. In such situations, in order for the sprouting of Clostridium botulinum to occur, it is essential that the skin wounds are not exposed to the air, that is, there is no oxygen circulating inside;
• Through the ingestion of food contaminated by its spores, which, once in the gastroenteric apparatus, germinate and produce neurotoxins. This situation affects almost exclusively the newborn, so much so that the resulting form of botulism is known to most as infantile botulism .

Clostridium difficile

Clostridium difficile is the responsible bacterial agent in humans, through two toxins, of a formidable form of colitis (inflammation of the intestine), known as pseudomembranous colitis .

Characterized by necrosis of enterocytes (ie intestinal cells), pseudomembranous colitis generally affects the colon colon and sigmoid colon intestinal tract, and causes symptoms such as watery diarrhea (characteristic symptom), abdominal cramps and pain, fever, nausea, anorexia, general malaise and weight loss.

In severe cases, pseudomembranous colitis can be lethal.

DIFFICULT CLOSTRIDIUM TOXINS

The two toxins of Clostridium difficile that cause pseudomembranous colitis in the human being are the so-called enterotoxin A and the so-called cytotoxin B.

Curiosity: what is an enterotoxin?

An enterotoxin is a toxin that targets the intestine, particularly the epithelial cells of the internal intestinal wall.

WHO IS AT RISK?

For healthy people, Clostridium difficile poses a minor threat, as it is unlikely to trigger an infection; the same bacterium is, instead, a serious danger for immunocompromised individuals and for subjects whose intestinal bacterial flora is strongly compromised due to prolonged antibiotic therapy. In fact, if for the first category of people the risk depends on an inefficient immune system to defend the organism from Clostridium difficile, for the second category of people the marked tendency to infection is linked to the fact that the intestinal bacterial flora represents a essential defensive bulwark against the proliferation of various pathogens, including Clostridium difficile .

Clostridium perfringens

Clostridium perfringens is a bacterium responsible, in humans, for an intestinal inflammation that:

• In most cases, it is mild and spontaneously resolved
• Only in rare circumstances, it is severe, highly debilitating and sometimes even deadly.

ROUTES OF CONTAGIOUS

Clostridium perfringens represents one of the main causes of food poisoning .

This means that human beings contract Clostridium perfringens infection by ingesting food contaminated by it.

HOW DOES IT WORK TO BOY THE INFECTION?

To initiate the infectious process, Clostridium perfringens uses some enterotoxins .

WHAT CAUSES IN THE MOST SERIOUS CASES?

During more serious infections, Clostridium perfringens has the potential to cause necrotising enteritis, various ulcers, fulminant toxaemia, dehydration, shock and, as already mentioned, even death.

Clostridium tetani

As already partly anticipated, Clostridium tetani is the bacterium that causes tetanus in human beings through one of its two toxins.

Tetanus is a very serious infectious disease, which subjects the striated muscles a little all over the body - especially those of the jaw, neck, back and chest - to spasms that prevent normal mastication, swallowing, breathing, correct posture etc.

Tetanus can be fatal (it occurs in about 20% of cases) and death generally occurs due to suffocation, swallowing pneumonia or respiratory failure.

TETANIC TOXIN

The toxin of Clostridium tetani which, in humans, causes tetanus is the so-called tetanospasmin .

Tetanospasmin is another important microbiological example of neurotoxin, or toxin with a tropism for the nervous system.

ROUTES OF CONTAGIOUS

The most frequent circumstances that lead Clostridium tetani to infect humans are skin wounds after the penetration of sharp objects, such as nails, splinters or thorns, on which spores are present.

Just as in the case of Clostridium botulinum, it is essential that the aforementioned wounds have no air passage, as this guarantees an oxygen-free environment, ideal for spore germination and toxin production.

Clostridium sordellii

Clostridium sordellii is a bacterium that, in humans, can cause pneumonia, endocarditis, arthritis, peritonitis, myonecrosis, bacteremia (rare) and sepsis (rare).

This bacterium, in reality, is much rarer than the previous ones, but it is clinically important, because it has as its preferred target women who have recently experienced a pregnancy, especially if it ended with a miscarriage or induced abortion.

ROUTES OF CONTAGIOUS

Despite numerous studies on the subject, it is still not completely clear how Clostridium sordellii infects humans.

uses

Important recent and past studies have shown that different Clostridium species can be used in the industrial field, in the production of fuel (eg: Clostridium thermocellulm ) or ethanol (eg: Clostridium ljungdahlii ), in the medical-aesthetic field, in the formulation of anti-wrinkle products ( eg: Clostridium botulinum ), in the pharmacological field, in the production of innovative anti-infective medicines (eg: Clostridium butyricum and Clostridium histolyticum ), and so on.

Therapy

As a rule, bacteria of the genus Clostridium are susceptible to different antibiotics, including penicillin G in high doses, tetracyclines, imipenem, metronidazole, vancomycin and chloramphenicol, and to some antibacterials, such as sulfa drugs.

How to kill a Clostridium in a vegetative state

The most effective way to kill the bacteria of the genus Clostridium in their vegetative state is to subject them to a heating whose temperatures exceed 72-75 ° C.

How to destroy the spores of a Clostridium

To destroy the spores of the bacteria belonging to the genus Clostridium, the most suitable solution is, even in this case, heat. However, it is necessary to point out that, in such circumstances, the temperatures to which the targets must be exposed must be decidedly high, even higher than 121 ° C.

Curiosity: are gamma radiations able to destroy the bacteria of the genus Clostridium?

The bacteria of the genus Clostridium are endowed with a certain resistance to gamma radiations; these bacteria, in fact, succumb only to remarkable radioactive exposures, higher than 30kGy (kiloGray).

How to inhibit the growth of Clostridium in foods

To inhibit the growth of Clostridium bacteria in foods, the addition of lysozyme, nitrites, nitrates and propionic acid to them is effective.