The Pathophysiology of Pneumonia || The Respiratory Infection by Bacteria, Fungi, and Virus

in StemSocial2 months ago

The human body is built to fight diseases before the introduction of external agent to fight them after infection. When so many of us are infected, we then start to look at our body and assume that it doesn't do enough to prevent the disease. I am not talking about the antibodies today, I am going to be discussing a disease caused by the inflammation of the lung parenchyma (Lung Tissue). That being said, a lot of you know where I am heading to, but for those who don't, I will be discussing the disease called Pneumonia.

Back to our body defense, the Normal Pulmonary Defenses (Lungs) includes the Nostrils, Communal Microbes, Mucociliary Apparatus, Alveolar Macrophage, and other innate immune system. So when a person is diagnosed with Pneumonia, do not see it like the body wasn't doing well to fight against it. That said, let's do a complete breakdown of Pneumonia.

Etiology Gives Background Understanding

According to World Health Organization, 14% of child death below the age of 5 is caused by Pneumonia. There are over 5 million incidence of Community Acquired Pneumonia yearly, in the United States. Pneumonia can be treated. There are several organisms causing pneumonia (causative agents), but popularly caused by Bacteria infection. These Bacteria include; the Gram Positive Streptococcus pneumoniae, gram negative Haemophilus influenzae common with patients having underlying pulmonary diseases, Mycoplasma pneumoniae, Chlamydia pneumoniae, Gram negative Legionella bacteria which can be found in natural fresh water environment, and can be contracted via cooling systems, Hot tubs and so on, Staphylococcus aureus which causes Staphylococcal pneumonia, Gram negative Klebsiella pneumoniae, and Pseudomonas aeruginosa.

Pneumonia can be caused by Viruses, and these viruses includes; Cytomegalovirus, Respiratory Syncytial Virus or para-influenza virus,Varicella Zoster, and Influenza Virus. Fungi also causes pneumonia, and example of fungi that causes pneumonia are Pneumocystis jiroveci Pneumonia common with immunocompromised people, Coccoides, Histoplasmosis Capsulatum.

Pneumonia can be acquired in different ways, and they are;

Community Acquired Pneumonia is the infection contracted by a person ho hasn't been in the hospital. This pneumonia is common with Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella bacteria, and Chlamydia.

Hospital Acquired Pneumonia is the pneumonia contracted in the hospital after being admitted for more than 48 hours. These types of Pneumonia are in most cases resistant to multiple drugs. Microorganisms responsible for HAP are Pseudomonas aeruginosa, Staphylococcus aureus (MRSA), and Klebsiella pneumoniae. Another type of hospital acquired pneumonia is the Ventilator-associated pneumonia (VAP) which develops often after long time of intubation (about 72 hours).

Health Care Associated Pneumonia which is a type of pneumonia associated with patients who live in health care facility, nursing home, or who have had exposure to health care settings in recent times.

The Pathophysiology

Pneumonia is the inflammation of the Lung parenchyma (lung tissues) resulting from infection. This infection can be acquired by inhalation of pathogens (75% mostly bacteria, viral, or fungal infection), and aspiration. Now, the reason why I talked about the normal pulmonary defenses before is that, We are normally expected to inhale microorganisms, but these defenses are responsible for fighting them. For instance, at the Cilia which contains the Pseudostratified Ciliated Columnar Epithelial tissue (P.C.C.E), also known as the Muco Ciliary Escalator, found in the linings of the trachea is a cytoplasmic extension, which helps to combat large bacteria, by trapping foreign bodies and help in expelling the foreign bodies through mucus. Another normal pulmonary defense is the Cough Reflex, which allows coughing when a foreign body gets into the wrong part of the system. Still on the pulmonary defense, is the IgA antibodies, which are part of the mucosal in the epithelial region. Also, in the defense of the pulmonary, is the Alveolar macrophages, present in the luminal surface of the alveolar space helps to engulf foreign matters.

Pneumonitis is the inflamation of the lungs tissues which is non-infective

The microbes can be aspirated from the upper respiratory tract, or from the GIT (macro aspiration). If the causative agent of Pneumonia (Streptococcus pneumoniae in most cases) is able to beat the normal pulmonary defense as a result of damage to them (which is usually triggered by smoking and alcohol), then the bacteria colonizes the bronchial, producing endotoxins which will damage the tissues. In the process of damaging the tissue, chemical such as Leukotrienes (Leukotriene b4) are released to trigger white blood cells and antibodies (Chemotaxis).. Once the bacteria endotoxins start to damage the tissue, other Leukotriene chemicals such as the Leukotriene C4, Leukotriene D4, and Leukotriene E4, will cause vascular permeability and constriction of bronchial muscles.(ncbi), (science direct). Just as the Leukotrienes are doing their job, and allowing the flow of blood into the area so white blood cells can attack the infection, they are also causing inflammation. The Alveolar Macrophage also, in the process of strengthening and defending the lower respiratory tract when engulfing isn't working much, would also release Cytokines (chemicals) which are the IL-1 (interleukin-1), and tumor necrosis factor, Chemokine-like IL-8 (interleukin-8), and G-CSF (granulocyte colony-stimulating factor), to help respond to the inflammation but in the process they cause leakages in the alveolar-capillary membrane where the inflammation exists, Pyrexia (fever), and shortness of breath. (Bacterial pneumonia).

With this, the person is already suffering from Pneumonia, which is divided into 4 stages, including Congestion (Usually between Day 1 and 2), where the fluid with pathogens, neutrophils, and macrophages starts to enter into the Alveolar (diffuse congestion) through the inflamed tissue, causing the Lung tissues to be boggy, and heavy. In the second stage, Red blood cells and fibrin, starts to enter into the alveolar, a stage known as Red hepatization (usually between day 4 to day 8). The affected area of the lungs starts to show red pink color. The next stage occurs 2 to 3 days after the Red Hepatization, and the stage is known as Grey hepatization (or late consolidation), In this process, the red blood cells get destroyed/disintegrated, thereby changing the color of the lungs to gray. When this stage is over, the next stage is going to be the Resolution stage. In this stage, the gray hepatization is broken down, and the exudates cleared out.

Patients with Pneumonia often have display signs during physical examinations which includes; Increase in heart rate (Tachycardia), Increase in Respiration rate (Tachypnea), Fever (Pyrexia), Cough with Sputum, shortness of breath (Dyspnea) or bronchial breath sounds. .

Treatment and Management

Since majority of pneumonia infections are bacteria infection, antibiotics can be used for treatment. Pneumonia treatment is dependent on the type of pneumonia. In cases of Ventilator-associated pneumonia (VAP) and Hospital Acquired Pneumonia (HAP), treatment and management should be in accordance with the ATS guidelines.

Image 1 ||
Image 2 || Wikimedia commons


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Pneumonia is a very common illness in Africa. Factors such as dust, pollen, and smoke can lead pneumonia. The idea that pneumonia comes from cold is very incorrect. Detailed writeup @eni-ola I always try to read your articles, they're always detailed and informative. I'm learning from you.

LOl... We are all learning from one another. It is good to have you here on my blog.

Yeahhh. You're welcome

Well detailed and educating piece
Thank you for this.

Thanks a lot for reading.