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Classification of Pneumonia

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Pneumonia can be classified as

  • Community-acquired pneumonia

  • Hospital-acquired pneumonia (nosocomial).

As the name suggests, community-acquired pneumonia is acquired by any person outside the hospital setting.

Sometimes, a person can get admitted to the hospital due to some other illness or for some surgery and get infected in the hospital. A hospital is a place where a number of patients arrive and depart for consultation, investigation, treatment or follow-up. Despite stringent methods to make sure that patients come and get treated and go without leaving any pathogens or microorganism behind, some organisms manage to survive all the aseptic precautions and thrive in the hospital setting. These cause pneumonia in a previously healthy individual who has come to the hospital for some other purpose. This infection is known as nosocomial pneumonia. It is defined as any pneumonia developing in an individual 72 h after being in a hospital.

Among community acquired pneumonia and hospital-acquired pneumonia (nosocomial)., nosocomial pneumonia is the most serious because of the simple reason that for an organism to survive in a hospital setting with all the aseptic techniques, the organism will usually have developed good resistance to most antibiotics and therefore will pose a significant challenge for treatment.

The organisms responsible for causing pneumonia can be divided as follows:   

  • Typical: Organisms causing typical pneumonia are the Streptococcus pneumoniae, Staphylococcus and Haemophilus species.
  • Atypical. Organisms known to cause the atypical pneumonia are the Mycoplasma, Legionella and Chlamydia species.


Streptococcus pneumoniae 

Streptococcus pneumoniae is the most common cause of bacterial pneumonia. It is usually of abrupt onset and accompanied by chills, fever, and production of a rust-colored sputum. A vaccine (Pneumovax) is available against S. pneumoniae and is recommended for infants, elderly and people with diabetes, chronic heart, lung or kidney disease.

This is usually well-managed with the use of antibiotics.

Antibiotics commonly used in the treatment of this pneumonia include

  • amoxicillin and clavulanic acid (Augmentin and Augmentin XR), 

Haemophilus influenza

Haemophilus influenza is another bacterium that causes pneumonia in the susceptible persons.

For treating this infection, antibiotics that can be used are

  • Amoxicillin and clavulanic acid,
  • Second- and third-generation cephalosporins,
  • Fluoroquinolones (levofloxacin [Levaquin]), moxifloxacin-oral (Avelox), gatifloxacin-oral (Tequin), and
  • Sulfamethoxazole and trimethoprim (Bactrim and Septra).

Mycoplasma pneumoniae

Mycoplasma pneumoniae is one of the atypical pneumonias. Symptoms include fever, chills, muscle aches, diarrhea and rash. This bacterium is the principal cause of many pneumonias in the summer and fall months.

Macrolides (erythromycin, clarithromycin, azithromycin and fluoroquinolones) are antibiotics commonly prescribed to treat Mycoplasma pneumoniae.

Legionnaire’s disease

Legionnaire’s disease is caused by the bacterium Legionella pneumoniae and is most often found in contaminated water supplies and air conditioners. It is a potentially fatal infection if not accurately diagnosed.

Pneumonia is just a part of the overall infection, and symptoms include high fever, a relatively slow heart rate, diarrhea, nausea, vomiting and chest pain. Older men, smokers and people whose immune systems are suppressed are at higher risk of developing Legionnaire’s disease.

Fluoroquinolones are the treatment of choice in this condition.

Pneumonia due to virus

The other major cause of pneumonias is virus. These pneumonias usually resolve over time with the body’s immune system fighting off the infection. It is important to make sure that a bacterial pneumonia does not secondarily develop. If it does, then the bacterial pneumonia is treated with appropriate antibiotics.

Pneumonia due to fungal infections

Apart from bacterial and viral sources that can cause pneumonia, fungal infections that can lead to pneumonia include actinomycosis, cryptococcosis, aspergillosis, histoplasmosis, coccidiomycosis, blastomycosis and nocardiosis.

These are responsible for a relatively small percentage of pneumonias in USA. Each fungus has specific antifungal and antibiotic treatments, which are amphotericin B, fluconazole (Diflucan), penicillin and sulfonamides.

Next page: Route of transmission of pneumonia

Written by :Healthplus24 team
Date last updated: July 31, 2012