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

Clostridium difficile is a gram-positive bacterium that belongs to the group of firmicutes and is also part of the bacterial flora of the intestine. It was isolated in 1935 by Hall and O'Toole.

It constitutes a bacterium of a pathogenic type, specifically at the intestinal level. Infections with these bacteria are very common in people who have been on a long-term antibiotic regimen.

Clostridium difficile. Source: See page for author, via Wikimedia Commons

This is a bacterium that in recent years has become a real problem, especially in hospitals, since the number of patients that is infected with it increases more and more. In addition, to this is added the high resistance it has to common hygiene measures.

Some specialists consider that perhaps this resistance is due to the development of a strain that has mutated, has acquired resistance to conventional drugs and is more virulent.

The age group most vulnerable to Clostridium difficile infection are the elderly, who by nature have an immune system more prone to depression. This has been proven by the numerous statistics that accompany the various studies that have been conducted on the subject.

Clostridium difficile is a bacterium that, if not treated in time, can cause serious complications, including death.

Taxonomy

The taxonomic classification of Clostridium difficile is as follows:

Domain: Bacteria

Division: Firmicutes

Class: Clostridia

Order: Clostridiales

Family: Clostridiaceae

Genus: Clostridium

Species: Clostridium difficile

Morphology

Clostridium difficile is a rod-shaped (elongated) bacteria. They have rounded edges and flagella on their surface. They are 0.5-3 microns wide by 6 microns long.

Cells are surrounded by a cell wall that is made up of a thick layer of peptidoglycan. It also has polymers, known as PSI, PSII and PSIII.

These polymers are similar to teichoic acid and lipoteichoic acid, present in other gram positive bacteria. The components of the cell membrane have been studied because they play an indispensable role in the therapeutic area.

In the cultures, slightly elevated, translucent colonies are observed, with crystalline mottling. Similarly, they give off a characteristic manure smell.

The DNA of this bacterium is concentrated in a circular chromosome, which has 29% nucleotides of cytosine and guanine. Likewise, it presents a circular plasmid that contains 28% nucleotides of the same type mentioned.

General characteristics

It is gram positive

Clostridium difficile turns purple when subjected to Gram stain. This indicates that its cell wall contains peptidoglycan, which, due to its structure, retains the dye molecules, causing it to adopt the mentioned color.

Produces spores

This bacterium produces spores when environmental conditions are unfavorable. These spores can survive for a period of about two years in hostile conditions. Once these change and become favorable, the spores germinate creating new cells of the bacteria.

Metabolism

Clostridium difficile has a metabolism that is mainly based on the fermentation of some sugars, the main one being glucose. Likewise, it also ferments fructose, mannitol, mannose and cellobiose.

Habitat

This bacteria is ubiquitous. It is present in the normal microbiota of the human gastrointestinal tract as a commensal. It is also found in soil, sand, and hay. It has also been isolated from farm animals, rodents, and domestic animals such as dogs and cats.

Is pathogenic

Clostridium difficile is considered a pathogen, since through spores it is capable of generating certain pathologies. It has a preference for the gastrointestinal tract, where it germinates and causes diseases such as pseudomembranous colitis.

Growing conditions

This bacterium can thrive under varied growth conditions. The accepted temperature range is between 25 and 45 ° C. Its optimum temperature is 30-37 ° C.

Produces toxins

The bacteria produce two toxins, A and B. Both toxins act at the level of the epithelial cells of the intestine, triggering a series of changes that lead to the development of pathologies such as Clostridium difficile-Associated Diarrhea, Pseudomembranous Colitis, and Diarrhea Associated with Antibiotics

It is catalase negative

This bacterium is not capable of synthesizing the enzyme catalase. This means that it cannot break down hydrogen peroxide (H ₂ O ₂) in water and oxygen.

Hydrolyzes gelatin

Clostridium difficile synthesizes gelatinase enzymes, which allow it to cause gelatin to liquefy. This is evident in the cultures, in which a transparent halo is observed around the colonies.

It is indole negative

This bacterium does not synthesize the group of enzymes known as tryptophanases. Because of this, it is not capable of breaking the indole out of the tryptophan amino acid molecule. This is a test that allows you to differentiate Clostridium difficile from other bacteria and even from others of the genus Clostridium.

It is urease negative

The bacteria are capable of hydrolyzing urea to carbon dioxide and ammonia. This is because it does not synthesize the enzyme urease, as it does not have the genes for this.

Does not reduce nitrates

Clostridium difficile does not synthesize the enzyme nitrate reductase therefore it cannot reduce nitrates to nitrites. This also constitutes a test of identification and differentiation of the bacteria.

Pathogeny

This bacterium is a recognized human pathogen. It causes some diseases such as pseudomembranous colitis. The bacteria enter the body orally, mainly through contact with infected people.

The course of infection depends on whether the vegetative forms or the spores are ingested. In the first case, the living forms of the bacteria are eliminated in the stomach, thanks to the high level of acidity there.

Rather, the spores are designed to withstand harsh environmental conditions, thus effectively resisting stomach conditions.

The spores manage to reach the small intestine and germinate there, thus producing the vegetative forms of the bacteria. These reach the large intestine where conditions are ideal for it to reproduce. Here it colonizes the mucosa, causing the presentation of the symptoms that characterize pseudomembranous colitis.

This disease can also be caused through another mechanism. When people are put on prolonged antibiotic therapy, this causes the gastrointestinal microbiota to become imbalanced.

This causes Clostridium difficile, which is a regular inhabitant of this flora, to proliferate uncontrollably, giving way to the disease.

Virulence factors

The virulence factors that contribute to the bacterium Clostridium difficile causing damage to the gastrointestinal mucosa are the following:

• Toxins (A and B): Both toxins have various effects on the cells of the intestine. These include: they indicate the production of toxins, hemorrhagic necrosis, in addition to the depolymerization of actin with loss of the cytoskeleton.
• Adhesins: they are molecules that are responsible for promoting the correct union of bacteria with human colonic cells.
• Hydrolytic enzymes: among these are: hyaluronidase, gelatinase and L-proline-aminopeptidase, among others. These enzymes produce hydrolytic activity. Likewise, they increase, through their mechanisms of action, the availability of nutrients in the intestine for the bacteria.
• Spores: As already indicated, spores survive adverse environmental conditions and even the level of heartburn.

Symptoms

Among the most prominent symptoms of intestinal pathology caused by Clostridium difficile can be mentioned:

• Fever
• Watery diarrhea
• Abdominal pain
• Sickness
• Anorexy
• Abdominal distension
• Dehydration
• General discomfort

At the level of the intestinal epithelium, certain lesions can be seen that indicate the evolution of the disease:

• Early lesion (Type I): here epithelial necrosis is observed, in which there are exudates and neutrophils in the colon.
• Type II lesion: it is an epithelial ulceration (volcano type), in the middle of the intact mucosa.
• Type III lesion: here there is an ulceration covered with a kind of membrane, which is made up of cellular debris and leukocytes.

View of intestine with Pseudomembranous Colitis. Source: By Klinikum Dritter Orden, München. Abteilung Innere Medizin I Vielen Dank an Christoph Kaiser für die Überlassung des Bildes zur Veröffentlichung!, via Wikimedia Commons

Diagnosis

When it is suspected that a person may be showing signs and symptoms of a Clostridium difficile infection, certain tests are performed to reliably diagnose it.

Among these tests are the following:

• Stool examination: it is the first option to diagnose this pathology. There are several tests that can be performed on stool, including: enzyme immunoassay, polymerase chain reaction (PCR), and cell cytotoxicity assay.
• Colon examination: Through a colonoscopy or sigmoidoscopy, the doctor can directly appreciate the characteristics of the mucosa of the large intestine.
• Imaging: These types of tests include x-rays or computed axial tomography (CT) scans. They are used to determine if there have been any complications from the infection. These types of studies are assigned to people with severe cases of Clostridium difficile infection.

Treatment

When the clinical picture is caused by the previous administration of antibiotics, the first measure is to suspend said medication. It is expected that with this measure the picture will be reversed.

If this does not happen, it is decided to administer an antibiotic treatment with drugs to which the bacteria are notably susceptible. Among these, the most recognized and used are metronidazole and vancomycin.

References

1. Biochemical test and identification of Clostridium difficile. Retrieved from: microbiologyinfo.com
2. Chu, M., Mallozi, M., Roxas, B., Bertolo, L., Monteiro, M., Viswanathan, V. and Vedantam, G. (2016). A Clostridium difficile Cell Wall Glycopolymer Locus Influences Bacterial Shape, Polysaccharide Production and Virulence. PLOS Pathogens. 12 (10).
3. Clostridium difficile. Retrieved from: microbewiki.com
4. Garza, R. The main virulence factors of Clostridium difficile and the role of this microorganism in pseudomembranous colitis. Taken from: amyd.quimica.unam.mx
5. Clostridium difficile infection. Taken from: mayoclinic.org
6. Institute of Public Health of Chile (2012). Clostridium difficile. Taken from: cl
7. Kirk, J., Banerji, O. and Fagan, R. (2017). Characteristics of the Clostridium difficile cell envelope and its importance in therapeutics. Microbial Biotechnology. 10 (1) 76-90
8. Meyer, L., Espinoza, R. and Quera, R. (2014, May). Clostridium difficile infection: epidemiology, diagnosis, and therapeutic strategies. Los Condes Clinical Medical Journal. 25 (3). 473-484