Definition and Overview

Bacterial pneumonia is a lung infection commonly caused by Streptococcus and Haemophilus influenza. When these bacteria enter the lungs, the body’s immune system tries to destroy them. This immune response leads to the inflammation and narrowing of the airway. When this happens, the lungs’ ability to bring fresh oxygen into the body and remove waste gases is compromised, resulting in various symptoms including breathing difficulty, shortness of breath, and feeling more tired than normal.

Pneumonia can also be caused by a viral infection. Although viral pneumonia produces the same symptoms as bacterial pneumonia, they are treated differently due to the structural differences of the microbes that cause them. Viral pneumonia mostly affects people with strong immune systems while bacterial pneumonia is commonly diagnosed in patients with weak immune system or recovering from a respiratory infection. While bacterial pneumonia can usually be treated with antibiotics, viral pneumonia does not respond to the said medication. Because of their differences, it is important that the patient is diagnosed properly so appropriate treatment can be provided. Most people respond quickly to medications but those with severe symptoms or underlying health problems may need to be treated in a hospital.

Causes of Condition

As the term suggests, the condition is caused by some types of bacteria with Streptococcus pneumoniae being the most common. Other bacteria that can cause it are:

  • Klebsiellapneumoniae

  • Moraxellacatarrhalis

  • Neisseriameningitidis

  • Staphylococcusaureus

  • Streptococcuspyogenes

This type of pneumonia can develop on its own or occur following a flu or viral cold. Often, the immune system is able to stop bacteria from reaching the lungs. However, if a person’s immune system is weak because of certain medical conditions or the bacteria is very strong, it can enter the lungs and cause infection. The same is the case in people whose ability to cough is compromised (such as those who are sedated, suffered a stroke, or comatose patients). When the bacteria reach the lungs, the body reacts and sends cells to attack the bacteria. This immune response is what causes inflammation and fluid build up in the lungs.

Key Symptoms

Bacterial pneumonia can cause minor or severe symptoms depending on the patient’s general health condition. These symptoms include:

  • Breathlessness

  • Changes in mental awareness

  • Chest pain

  • Chills

  • Confusion

  • Coughing out phlegm and bloody mucus

  • Difficulty breathing and eating

  • Fast heartbeat

  • Fatigue

  • Persistent high fever (39C or higher)

  • Decreased appetite

  • Nausea

  • Restlessness

  • Sweating

  • Vomiting

If not treated promptly, patients may suffer from the following complications:

  • Bacteremia - Bacteria in the lungs have the potential to spread to other organs via the bloodstream. In many cases, it does not cause any symptoms but if bacteria accumulate in certain organs, they can cause organ failure. In people with weakened immune system, bacteremia can be more serious and can lead to sepsis.

  • Lung abscess - A potentially life-threatening condition characterised by the collection of pus in the lung. It can be treated with antibiotics but in some cases, the pus has to be drained by inserting a long needle or tube into the chest. When left untreated, it can cause bleeding in the lungs.

  • Pleural effusion - Refers to the fluid build up in the pleural space, which can result in breathing difficulty and permanent scarring.

Who to See and Types of Treatments Available

Patients who have a weak immune system must seek emergency care if they experience chest pain, shortness of breath, confusion, and are coughing up green, yellow or brown sputum. This is important because high-risk patients have low levels of infection-fighting white blood cells. Thus, the infection can easily progress to sepsis and death. High-risk patients include:

  • Very young children and patients over 65 years old

  • Patients with HIV or AIDS

  • Organ transplant patients

  • Cancer patients currently undergoing treatment

  • Malnourished individuals

  • Patients with chronic medical conditions, such as diabetes, asthma, and hepatitis, among others

Bacterial pneumonia is diagnosed through a physical exam, chest x-ray, and sputum and blood tests. Other tests that may be performed include pulse oximetry (measures patient’s oxygen level), computed tomography (CT) scan (to obtain clear and detailed images of the lungs), and pleural fluid culture (determines the type of infection).

Bacterial pneumonia is treated with antibiotics to cure the infection. Patients who are otherwise healthy often recover within a week. Other medications that are often provided to relieve patients’ symptoms include:

  • Cough medicine

  • Fever medicine

  • Pain relievers

In severe cases, doctors recommend hospital care especially if the patient is older than 65 years old or younger than 2 months, showing signs of mental deterioration or organ failure, or require breathing assistance.


Pneumonia is the third most common cause of hospitalisation in the United States following births and heart disease. Every year, up to 10 million people develop the condition and at least one million of them require hospitalisation. The death rate for pneumonia patients who require hospitalisation is up to 25%. This number can be as high as 70% for those who are already hospitalised due to other diseases. Although millions of patients respond very well to treatment, pneumonia kills up to 70,000 individuals every year.


  • Lim, W.S., S.V. Baudouin, R.C. George, A.T. Hill, C. Jamieson, I. Le Jeune, et al. “British Thoracic Society Guidelines for the Management of Community-Acquired Pneumonia in Adults: Update 2009.” Thorax 64 (Suppl III) 2009: 1-55.

  • United States. Centers for Disease Control and Prevention. “Pneumococcal Vaccination.” Dec. 10, 2015. vaccination.html.

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