Bacterial Pneumonia Overview
Pneumonia is an infection of the lungs. People with pneumonia usually complain
of coughing, mucus production, fever, shortness of breath, and/or chest pain.
- The body's immune system usually keeps bacteria from infecting the lungs. In bacterial pneumonia, bacteria reproduce in
the lungs, while the body tries to fight off the infection. This response to bacterial invaders is called inflammation.
- When the inflammation occurs in the alveoli (microscopic air sacs in the lungs) they fill with fluid.
The lungs become less elastic and cannot take oxygen into the blood or remove carbon dioxide from
the blood as efficiently as usual.
- When the alveoli don't work efficiently, the lungs are less able to extract oxygen from the air. This causes the feeling of being short of breath (dyspnea), which is one of the most common symptoms of pneumonia. Inflammation
is the body's attempt to destroy infection, and causes many of the other symptoms
of bacterial pneumonia, including fever and chest pain.
- Pneumonia can be very serious, because it directly
interferes with the body's ability to exchange carbon dioxide and oxygen.
- Pneumonia is different from acute bronchitis
(another disease that can cause fever, cough, chest pain,
and shortness of breath) because acute bronchitis is caused by inflammation in the air
passages (called bronchi) leading to the alveoli, not the alveoli themselves. Sometimes it is very difficult, even for a doctor, to tell pneumonia and bronchitis apart. The symptoms and physical examination can be identical. Sometimes a
X-ray is the only way to distinguish
pneumonia from bronchitis. There is also an entity in which both the airways and air sacs are involved with infection, and this is referred to as bronchopneumonia.
Bacterial Pneumonia Causes
- Most pneumonia is caused by bacteria or a virus. Pneumonia from
any cause can occur at any age, but people in certain age groups are at higher
risk for certain types of pneumonia.
- The most common cause of bacterial pneumonia is a type of bacteria known as Streptococcus pneumoniae. Haemophilus influenzae, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila are some other major bacteria that cause pneumonia.
- People who inhale toxic materials can injure the lungs and cause chemical pneumonia. This is more accurately referred to as chemical pneumonitis, since the process is mainly due to inflammation not from an infectious source.
- Fungi can also cause pneumonia. In certain areas of the United States, specific fungi are well known. Coccidioidomycosis, usually seen in the Southwest,
is a type of fungal infection that causes a pneumonia called "San Joaquin fever" or "Valley fever." Histoplasmosis (seen primarily in the Midwest) and blastomycosis (seen primarily in the Southeast) are
other fungal diseases that cause pneumonias.
- The most common way you catch pneumonia is to aspirate bacteria from the upper airway, usually
the oral cavity. Other ways to catch pneumonia can be by breathing in infected air droplets from someone who has pneumonia. In some cases, the bacteria can be generated by an improperly cleaned air conditioner or
Jacuzzi. Yet another source of infection in the lungs is spread of an infection from somewhere else in
the body, such as the kidney. Bacteria can enter the bloodstream from any source and be deposited in the lungs, resulting in pneumonia.
- The risk of catching pneumonia is determined by the specific bacteria, virus, or fungus, the number of
organisms the person inhales, and the body's ability to fight infections.
- A person cannot "catch pneumonia" by not dressing properly for cold weather or by being caught in the rain.
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