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Pathogenicity and virulence of microorganisms. Virulence is ...

The human body is home to about 100 trillion bacteria. Scientists of our time are only now fully aware of how these complex communities interact with man. They affect the processes of digestion, the immune system and, perhaps, even mental well-being. However, not all bacteria can coexist with the human body in peace and harmony. Pathogenic is a microorganism that can cause disease in plants, animals or insects. Microbes express their pathogenicity through virulence. So, what is virulence?

The concept of virulence

Virulence is the term for indicating the degree of microbial pathogenicity. Consequently, the determinants of the virulence of the pathogen are any of its genetic, biochemical or structural features that allow disease.

The relationship between the host and the pathogen is in constant dynamics, as everyone is able to change the activities and functions of others. The outcome of such relationships depends on the virulence of the pathogen and the relative degree of resistance or susceptibility of the host. An important role is played also by the effectiveness of the protective mechanisms of the body.

Virulence factors are directly related to properties that allow harmful microorganisms to get into or onto the host's body and lead to disease. They include bacterial toxins that promote pathogenicity.

Important concepts

Invasiveness is the ability to penetrate tissues. It includes mechanisms for the possible colonization and production of extracellular substances that contribute to invasion and the ability to circumvent or overcome certain protective mechanisms.

Toxogenicity is the ability to excrete toxins. Bacteria can produce two types of toxins: exotoxins and endotoxins. Exotoxins are released from bacterial cells and promote the growth of bacteria. Endotoxins are a cellular substance.

Bacterial toxins, both soluble and cell-related, can be transported by blood and lymph and cause cytotoxic tissue effects in areas remote from the initial entry point. Some bacterial toxins can also create colonies, participate in the invasion.

Pathogenicity and virulence of microorganisms

Pathogenicity is the body's ability to cause disease. This ability is a genetic component of the pathogen, which harms the receiving side. For conditionally pathogenic microorganisms, this ability to cause the disease is not congenital. Pathogens can express a wide range of virulence.

Virulence is a concept that is inseparably linked with the concept of pathogenicity. The degree of virulence usually correlates with the ability of the pathogen to multiply in the host organism and may depend on certain factors. Virulence factors contribute to pathogenicity, that is, they help to cause the disease.


Many have repeatedly drawn attention to various ads about advertising products that claim that 99% of microbes are being killed. Pathogen is a term used to describe small organisms (bacteria and viruses) that cause various diseases. In biological terminology, it is also known as a causative agent. There are several types of pathogens that cause various diseases, ranging from a common cold and ending with oncological diseases.

Pathogenic microorganisms affect humans in different ways, depending on their virulence. Virulence is a term that is used to describe the effectiveness of a specific pathogen. The more virulence the pathogen possesses, the more negatively it will affect human health.

About the factors of virulence

Virulence factors are characteristics of pathogenic microorganisms that determine which virulence the pathogen possesses. The more of them, the more likely that it will cause the disease. These factors give an advantage in the fight against the human immune system, and the more of them, the more destructive they can be.

There are several different types of virulence factors that may or may not be present in a particular pathogen: colonization factors, enterotoxins and hemolysins. Virulence is a quantitative feature that represents the degree of pathology caused by a microorganism. This is a sign that expresses the interaction between the pathogen and the carrier. Virulence usually correlates with the ability of the pathogen to multiply. It may also depend on the vector and environmental factors.

A bacterial agent is usually defined as any bacterium that can cause disease. Its ability to cause disease is called pathogenicity. Virulence of the microorganism is directly dependent on the nature of the infection and is an indication of the severity of the disease that it causes.

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