Community Acquired Pneumonia

Community acquired pneumonia (CAP) is a serious infection that causes inflammation of the lungs and is generally acquired outside the hospital or long term care facility. The infection affects the air sacs in the lungs and fills them with pus or other liquid, and thus making it difficult for oxygen to penetrate through the lungs to reach the bloodstream. If not treated promptly and properly with antibiotics, CAP spreads throughout the body, and thus can lead to death, especially in old people or people with weakened immune systems.

Community acquired pneumonia usually occurs in children or the elderly, or in people with an underlying pathology. Community-acquired pneumonia is commonly caused by streptococcus, however there are other organisms that are known to cause community acquired pneumonia and they are Legionella, Haemophilus influenzae, mycoplasma, chlamydia, and viruses. Staphylococcus may rarely be associated with community-acquired pneumonia, but it often causes hospital-acquired pneumonia. Purulent sputum production cough, pleuritic chest pain, shortness of breath, fevers and chills are typical symptoms of community-acquired pneumonia.

The elderly patients show vague and non-specific symptoms. The symptoms include headache, diarrhea, malaise, confusion, falling, and decreased appetite. Diagnosis is done with the help of chest x-ray. In general, patients suspected with CAP, with test findings confined to the lungs and no laboratory evidence of extrapulmonary involvement, suffer from CAP caused by a typical pathogens. Patients suffering from pneumonia and show evidence of extrapulmonary involvement or laboratory findings such as elevations in liver function test results, have atypical pneumonia.

Pneumonia is an infection of the lung parenchyma and community acquired pneumonia is acquired outside of hospitals, Nursing homes or extended-care facilities. Nosocomial pneumonia is also an example of pneumonia acquired in the hospital setting. It may take hours or days for the signs and symptoms of acute pneumonia to develop, while it may take over weeks to months for the clinical presentation of chronic pneumonia to evolve.

Though Streptococcus pneumonia is the common pathogen in communityacquired pneumonia, a variety of other pathogens is known to cause pneumonia in the community. The order of importance depends on the location and population studied. These pathogens are Haemophilus influenzae, Mycoplasma pneumoniae, and influenza A, and other newer pathogens such as Legionella species and Chlamydophilia pneumoniae. Other common causes known to cause CAP in the immunocompetent patient are Moraxella catarrhalis, Mycobacterium tuberculosis, and aspiration pneumonia. In about 30% to 50% cases of community acquired pneumonia, the causative agent remains unidentified.

Many pathogens like Bacillus anthracis, Francisella tularensis, and Yersinia pestis are listed as potential agents of bioterrorism. The mode of transmission is through the respiratory route. A more elaborate discussion on the agents of bioterrorism is found in the chapters of chemical and biologic weapons in the Cleveland Clinic Disease Management Project.

Nursing home-acquired pneumonia is an example of pneumonia caused by community-acquired pathogens. However, it is observed that there is an increased influence of pathogens such as S. aureus (aspiration or following influenza) or gram-negative organisms that have relatively low frequency in the community.

Community Acquired Pneumonia Causes

Community acquired pneumonia spreads when an individual inhales droplets of sneeze or cough from an infected person. Hence it is easily transmitted by close person to person contact. Several different organisms including bacteria, viruses and fungi are responsible for causing CAP. The most common organism causing CAP is a bacterium known as Streptococcus pneumonia. Although many organisms or “bugs” have been confirmed as causing CAP, around 30% to 50% of pneumonia cases are believed to have an unknown cause. This means that the actual “bug” responsible for causing the disease has not been identified or isolated even after laboratory testing.

Streptococcus pneumonia(pneomococcus) and other bacterial pneumonias are usually the most serious and constitute the most common cause of CAP especially in adults. In young children, especially those between 2 and 3, respiratory viruses are the most common causes of pneumonia. As the school going age approaches, Mycoplasma pneumonia becomes more common.

In case of the elderly or those who are debilitated, it has been observed that bacterial pneumonia may follow influenza or even the common cold. Pneumonia can even be contracted by people admitted to hospitals for other ailments. This often proves to be more dangerous as the patient’s immune system has already suffered a setback from the original ailment. There is also the risk of catching an infection from bacteria are resistant to antibiotics.

Risk factors comprise of typical characteristics that increase the probability of developing a condition. The more the risk factors prevailing, the higher are the chances of catching the infection. You would be at increased risk of developing CAP if one or more of the following factors apply to you:

  • Are over 65 years of age.
  • Have other medical conditions or a combination of conditions like:
    • Chronic obstructive lung disease (COPD) or other chronic lung ailments
    • diabetes mellitus
    • chronic kidney disease
    • heart failure
    • coronary artery disease
    • cancer
    • chronic liver disease
    • cystic fibrosis
  • Are a smoker.
  • Have been habitually exposed to chemicals and pollutants used in agriculture, industries or construction. Prolonged exposure to these pollutants could damage the lungs, leading to lung infection and rendering the lungs more vulnerable to infection.
  • Are an alcoholic.
  • Have a weakened immune system.

Community Acquired Pneumonia Symptoms

Community Acquired Pneumonia sometimes is presented after an episode of cold, flu, or any condition that gives access to bacteria to infect the airways. The symptoms of Community Acquired Pneumonia (CAP) may vary and are generally similar to that of common cold or flu. This variability in symptoms may sometimes make it difficult to recognize pneumonia. Many people assume the symptoms to be of difficult case of cold. However, if it is not diagnosed and treated well in time, CAP can pose a threat and could be fatal to life.

Some easily recognizable community acquired pneumonia symptoms are as follows:

  • night sweats
  • shaking and chills
  • a cough that expels sputum, which is usually rust or burnt orange color
  • shortness of breath
  • chest pain worsened by deep breathing or coughing
  • fever

In addition to the symptoms mentioned above, the following symptoms could be associated with this disease:

  • Excessive sweating and clammy skin
  • Excessive fatigue
  • Confusion in older people
  • Headache
  • Loss of appetite

Community Acquired Pneumonia Diagnosis

Persons who have pneumonia experience strenuous, labored or rapid breathing. Listening to the chest with a stethoscope or by percussion (tapping of the chest wall) may reveal a crackling sound and other abnormal sounds.

Pneumonia is confirmed by taking the following tests:

  • Chest x-ray
  • Gram’s stain and culture of sputum to identify the symptom causing organism
  • CBC to verify the white blood cell count which if high, suggests a bacterial infection
  • Arterial blood gases to check how well oxygenated your blood is
  • Thoracic CT
  • Pulmonary ventilation/perfusion scan
  • Pleural fluid culture to check for fluid in the space surrounding the lungs

Community Acquired Pneumonia Treatment

The treatment for community acquired pneumonia is determined by the organism responsible for the infection. If the cause is confirmed as bacterial and if the infection is not severe, then it can be cured by oral antibiotics at home itself. If on the other hand, the infection is severe and the patient is having difficulty breathing, or is suffering from other chronic conditions, then intravenous (administered into the vein) antibiotics could be required and therefore hospitalization would be required. If the infection is viral, then the only treatment would be to provide relief from symptoms through supportive care (fever reduction with acetaminophen), as there is no cure for a virus.

There are various treatment options and courses available and the specific drugs prescribed by doctors could differ. Antibiotic drug resistance in a precise area and clinical expertise or preference may determine a doctors choice of drugs to treat CAP.

At the first visit, the doctor may ask you about your past medical history and may conduct a physical examination. A chest x-ray could be recommended. The doctor would then gauge if the infection is life threatening. A laboratory test of sputum, urine and blood may be advised. Doctors normally prescribe “empiric therapy” which is based on the suspected cause (either bacteria, virus, fungi) as the exact organism causing the infection has not been identified at the start of the treatment. Once the exact cause of the infection has been identified, therapy can be tailored to treat that specific organism.

When CAP patients require hospitalization, IV antibiotics along with oxygen therapy would be initiated to assist in breathing. Studies have confirmed that bacterial CAP can be effectively treated within 5 to 14 days of antibiotics. However, if the cause of infection is identified to be from specific bacterial organisms like Legionella or Pseudomonas or fungal organisms, then the duration of therapy could be prolonged. It is important to complete the course of antibiotics prescribed by the physician. Often people stop taking medicines once they feel better. This leads to antibiotic resistance and causes an even more severe relapse of the infection. When an organism develops a resistance to the antibiotic, it also has the potential to prevent the antibiotic from showing positive results in treating others with the same infection within the family or community.

Measures to be taken at home include:

  • Drinking plenty of fluids to wash away secretions and to bring up phlegm.
  • Get lots of rest. Assign the cooking and even doing the light work around the house to someone else.
  • Control fever with acetaminophen or aspirin. Please note that Aspirin must NOT be given to children.

For patients who have been hospitalized, respiratory treatments to eliminate secretions may be required. Steroid medications may also be used to reduce wheezing in case of underlying lung disease.