The 9 types of Pneumonia (causes, symptoms and treatment)

This lung disease can be due to a wide variety of causes.

Any condition that jeopardizes the health of the lungs is very serious.. An essential activity for the proper functioning of the body is carried out in this organ, and it is none other than the exchange of gases.

In other words, it is where oxygen (O2) is collected, a necessary element for the cells to obtain energy for their functions; and carbon dioxide (CO2) is released, a residual element of this process of obtaining energy and which is toxic for the cells, so it is necessary to expel it from the body. So any abnormality that affects this exchange is detrimental to the health of the person.

Pneumonia: lung inflammation

There are many diseases that affect the lungs, one of the most common being pneumonia. It is so important that this condition is among the most frequent causes of death in the world.

Various criteria are used to differentiate between different types of pneumonia, but they all share the fact that they are inflammations due to an immune response to an infectious agent in the alveoli (gas exchange area) and surrounding tissues.

The usual symptoms of pneumonia are cough with sputum formation, breathing difficulties, chest pains, fever and chills. The level of severity depends on the infectious agent..

The use of criteria to identify pneumonias is a necessary method to know which pneumonia the patient is suffering from and to follow the appropriate treatment for improvement. Pneumonias are a group of diseases, each one caused by a different microorganism. There are many ways to separate the different types of pneumonia, here we will expose several of these criteria, but they are not the only ones for this task.

Types of pneumonia according to the causative agent

The classic classification separates pneumonias by the pathogen that causes it, but at the clinical level it is not very useful, because at the beginning of a treatment samples have not yet been analyzed to know the infectious agent that the patient has. However, for a generalized study of the disease it is ideal.

1. Gram-positive bacteria

There is a criterion for separating bacteria which is the use of gram staining.The staining of the cell differentiates gram-positive and gram-negative bacteria according to how the cell is stained. In the case of those positive in this staining, there are two well known cases.

Pneumococcal pneumonia is a type of pneumonia caused by Streptococcus pneumoniae bacteria, commonly known as pneumococci. This is the most frequent case, since there are almost 80 different types of pneumococci, and each one needs its own antibody, i.e., being infected by one of these does not immunize you from the rest. It is usually generated after a viral infection that weakens the respiratory tract, facilitating its entry into the lungs.

The other case is staphylococcal pneumonia, an infection caused by Staphylococcus aureus bacteria. It is rare in cases outside hospitals, however, it is more common to get infected inside them, since it usually affects children and elderly people, or people with previous pathologies. The appearance of pus with this bacterium is very typical.

2. Gram-negative bacteria

Having seen the first group, it is now time for the gram-negative bacteria. Unlike the first group, these are usually much more aggressive and, therefore, they are a type of bacterium that can be and, therefore, are a more serious type of pneumonia. Some example bacteria are Klebsiella, Legionella or Pseudomonas and are infections more likely to be acquired in hospitals. They have a great capacity to damage tissue relatively quickly, which is why they are very serious conditions, with the possibility of being lethal.

For example, the bacterium Hemophylus influenzae, especially its type B strain, causes serious infections in the meninges or lungs in children under six years of age, but thanks to its vaccine it does not cause major problems today.

3. Atypical pneumonias

This group includes the types of pneumonias caused by bacteria that are not included in the previous ones.They also generate a much milder pneumonia than those mentioned above, which would be the typical one. Mainly here we find microorganisms of the genus Mycoplasma and Chlamydia. A good example of these is pneumonia caused by Mycoplasma pneumoniae, which is the most frequent cause among people between 5 and 35 years of age.

4. Viral pneumonias

Inflammations in the lungs can also be caused by the entry of viruses, such as influenza or herpes. The main problem with this is that they are not treated with drugs, and antivirals are only used in severe cases.

5. Fungal pneumonias

This type of pneumonia is usually very mild and even the infected person does not realize that he/she has it. They are caused by Fungal infection in the respiratory tract, mainly by these three: Histoplasma capsulatum, Coccidioides immitis and Blastomyces dermatitidis.

Pneumonias according to fungal area

Not all infections affect the same area of the respiratory system or in the same way.. Therefore there is also another criterion to separate pneumonia.

Thus we can distinguish between lobar pneumonia, which affects a whole lobe of the two lobes of the lungs; bronchopneumonia, which affects both the lungs themselves and the airways (the bronchi); necrotizing pneumonia, in which the affected areas of the respiratory system develop necrosis or tissue death; or interstitial pneumonia, inflammation affecting the connective tissue of the alveoli.

The criterion of necrosis formation is very useful to identify the cause, since they are usually anaerobic microorganisms, i.e. they cannot live in an oxygen environment.

Depending on the area of acquisition

This is a more resolute classification for rapid clinical identification and refers to whether the pneumonia was acquired outside or inside a hospital. The microorganisms are not the same in these two environments, which makes it possible to rule out an infectious agent simply by knowing where the patient was infected.

The first type of pneumonia is called nosocomial or hospital-acquired pneumonia, and are those that manifest themselves after being admitted to a hospital for more than 48 hours and were not incubating prior to entering the center. Here the infectious agents are more resistant, since a hospital has a higher level of hygiene than many other locations or people are weakened and therefore are admitted to a hospital.

For the rest, they are grouped into community-acquired or community-acquired pneumonia, and as the name indicates, this is when the infection has not originated in a health center.

Depending on the host

The last criterion to be mentioned to differentiate pneumonias is according to the patient's immunity. As is logical, it is not the same for a person to have a functioning immune system as it is for a person not to have a functioning immune system.and this serves to identify the infectious agent that causes it. This criterion is used to differentiate between immunocompetent and immunocompromised pneumonias.

It should be remembered that the defensive system stops many of these pathogens before they can act, so their partial or total absence is a risk factor. Opportunistic infections take advantage of this absence of defense, since they are microorganisms that under normal conditions do not cause disease.

The case of Coronavirus

Finally, we can expose a case that can cause pneumonia that affects us all because of its global reach. I am talking about none other than SARS-CoV-2, the cause of COVID-19.. Commonly called coronavirus, it is a virus of the Coronaviridae family, which infects its hosts in their respiratory tract.

The general cycle of a virus within its host is to infect cells, where it injects its genetic content and takes control of the host's mechanisms for the duplication and replication of that material. In addition, it also uses it for the manufacture of other protein components that form the virus (such as the capsid, where the genetic content is stored). In other words, the virus dominates other cells to manufacture copies of itself and thus grow in number. Once a limit of units is reached, it activates the destruction of the cell for the release of the virus.

In the case of coronavirus, the pathogen invades cells of the respiratory tract, mainly the alveoli, so that the infection and destruction of cells in this tissue affects our breathing. Therefore, its main symptoms are fever (infection), cough and shortness of breath (affects the gas exchange area). In more severe cases, pneumonia and acute respiratory syndrome, a pulmonary insufficiency due to the accumulation of blood (edema) in the organ, are generated.

The general problem with viruses is that no medication is used for their treatment, since antiviral drugs are of restricted use. Normally, the aim is to minimize the symptoms and make use of devices that facilitate the functions (e.g. respirators). And the vaccine is a preventive element to avoid contracting the disease. So in this case, what is sought as the quickest solution is an effective treatment that helps to minimize the damage of the virus and most importantly, to take preventive measures to stop the spread.

Bibliographic references:

• Dr. Percy Miranda Paz. "Pneumonia". 2004. https://www.saludarequipa.gob.pe/epidemiologia/ASIS/docs/Doc/Sala%20situacional%20Neumonias.pdf

• Carlos José Álvarez Martínez. "Pneumonia: Concept, classification and diagnosis". https://www.neumomadrid.org/wp-content/uploads/monogix_1._neumonias-concepto.pdf

• General Council of Pharmaceutical Associations. "Coronavirus COVID-19". 2020. https://www.portalfarma.com/Profesionales/campanaspf/Asesoramiento-salud-publica/infeccion-coronavirus-2019-nCoV/Documents/Informe-tecnico-Coronavirus.pdf