Pathogen, Pathogenesis, Pathogenicity: Definition and Examples

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What are Pathogens?

According to the norms of the nature, we are all part of the environment, where remaining parts are being filled by microorganisms and other species of animals, insects and plants.

These micro-organisms are classified as infectious and non-infectious organisms. The organisms which cause infections are generally described as pathogens.

They include virus, bacteria, fungi and other protists. Where as the non-infectious organisms includes organisms like Lacto bacilli which plays a very important role in diary industries.

Generally, pathogen refers to “suffering” in Greek terms; which is a characteristic of an organism that causes disease.

Pathogen, Pathogenesis, Pathogenicity- Definition and Examples 1

Pathogen can also be termed as infectious agent or simply as germ. The term pathogen came into existence in the year 1880s, which is typically used to describe a virus, bacterium, protozoan, or fungi.

In some cases, small organisms such as small worms and tiny insects can spread diseases.

Such types of organisms transmitting diseases is referred to as parasites. However, these pathogens and parasites are in common parlance of causing and transmitting infectious diseases.

Thus, the study involving pathogenic organisms is referred to as microbiology and the study which involves parasites are known as parasitology.

Pathogens uses several mechanisms to invade a host body. There are many principal pathways which have different episodic time frames; however, soil has the longest potential to harbor a pathogen. Diseases that are caused by pathogens are known as pathogenic diseases.

What is Pathogenicity?

Pathogenicity generally refers to the capacity of the pathogens to cause diseases.

Pathogenicity is similar a term to that of virulence in meaning, but some authorities have distinguished this in a qualitive form where as the other is known as quantitative. According to this, an organism is said to be pathogenic or not.

In simple words, pathogenicity is the ability of a pathogenic organism to cause disease.

This ability of the organism to produce disease is characteristic feature of an organism, which they acquire during their effort for surviving in the host.

The host may be either animal or plant or any other species including humans.

Types of Pathogen

Pathogens are of different types and they can spread by various means, but most commonly they spread by means of skin contact, or while transferring body fluids or through contaminated surface contacting.

Some pathogens exist as air borne particles.

The most common type of pathogens are bacteria, viruses and fungi. Diseases caused by viral pathogens are mostly common cold, yellow fever, flu, dengue fever, etc.

At the same time diseases caused by bacterial pathogens includes urinary tract infection, tuberculosis, gonorrhea, etc. and the most commonly caused fungal infections includes thrush, ringworm etc.

How Pathogens are Classfied?

Generally, pathogens are classified into four main categories depending on the classes of pathogenicity relying on the general risk analysis and the assessments which is present in practical and theoretical frame works.

I. Class 1

 The species coming under this class should have the following criteria.

 They must not be a part of group of which causes diseases in humans or any animals.

 They are proven to be safe in the past history under the conditions, which does not sort any kind of restrictions physically despite taking an account that species have difference in virulent strains within them.

 The species belongs to this class, but it also has relations with a particular gene which could create pathogenicity in animals and humans. This type of species can be put in an exceptional position in this group depending upon the degree of attenuation.

II. Class 2

The species which belongs to this class causes serious diseases in humans and often transmits within humans while having the important prophylaxis.

II. Class 3

The species belonging to this class has the ability to cause serious diseases but it can be treated with necessary therapies.

IV. Class 4

The species belonging to the class causes serious human diseases which disseminates in the human population and where no adequate therapy exists for this particular disease.

Types of Pathogen

Pathogens are classified into four types commonly as viruses, bacteria, fungi and parasites.

I. Virus

Viruses are made up of a piece of genetic code, namely as DNA or RNA and it is protected by a protein coat around itself.

When the individual is affected with viruses invade the host cells in our body and it further replicates and produces more viruses.

After replication, the new viruses are released from the cells of tends starts multiplying again. The hosts which damages the infected cells.

Some viruses remain dormant for a particular period of time. When this occurs in the host, the affected individual gets recovered from the infections and gets sick again. But antibiotics does not help in killing the viruses, antiviral medications are taken for this kind of viral infections.

II. Bacteria

Bacteria is one of the kinds of micro-organisms which is made up of a single cell. They are found in diverse, having variety of shapes and characteristics.

These pathogens have the capability to live in any type of environment inclusive of the human body.

Not every bacterium has the capability to causes diseases. Some type of bacteria’s plays a beneficial role.

Our body is prone to many kinds of bacterial infections when our immune system gets attacked by the viruses.

This diseased state of our body due to viruses enables the harmless bacteria to become infectious. Usually, antibiotics are used to treat the infections caused by bacteria.

III. Fungi

There are about millions of species of fungal species in the earth. But only 300 species are known as pathogens including the indoor and the outer environmental.

These pathogens often cause infections when they are overgrown. Fungal cells consist of a nucleus and other components and are surrounded by a protective cell wall. This complex structure makes them difficult to kill.

IV. Parasites

Parasites are the organisms which behave like tiny animals which lives in the host and feeds themselves through the host tissues.

Parasitic Infections are more commonly found in tropical and sub-tropical regions. There are many types of parasites which causes diseases in humans. Such type of parasites includes protozoa, helminths and ectoparasites.

Pathogen Citations


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