Bacterial pneumonia is the inflammation and accrual of fluid in the alveoli of the lungs caused by bacterial infection. Pneumonia may also be caused by viral or fungal infection. There are many different types of bacteria that can cause pneumonia. Bacterial pneumonia is most often caused by bacteria being inhaled into the lungs, though if there is bacterial infection elsewhere in the body, it can also enter the lungs through the bloodstream.
The symptoms of bacterial pneumonia are similar to those of other types of pneumonia. The include fever and chills, cough, shortness of breath, chest pain, and in severe cases - coughing up blood. Bacterial pneumonia, like other forms of bacterial infection, is treated with antibiotic medication.
Bacterial pneumonia is most often caused by one of the gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus, both of which are often present in the throat, nose, or skin of healthy individuals. Gram-negative bacteria that can cause the disease include Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Moraxella catarrhalis, and Pseudomonas aeruginosa. Many of these bacteria live in the gastrointestinal tract in healthy individuals and cause pneumonia when particles of a product of the gastrointestinal tract, such as vomit or feces, are inhaled.
The atypical bacteria responsible for bacterial pneumonia are the least common cause of the condition, but also result in more serious symptoms. Atypical bacterial pneumonia may not present with the increased white blood cell count that is common to typical bacterial infection in the lungs, and it may not respond to common antibiotics. Some atypical bacteria that can cause pneumonia are Coxiella burnetii, Chlamydophila pneumoniae, Legionella pneumophila, Mycoplasma pneumoniae, and Yersinia pestis.
Coxiella burnetii causes Q fever, a potentially fatal flu-like disease. If it leads to pneumonia, Q fever can cause acute respiratory distress syndrome (ARDS), a life-threatening condition. Chlamydophila pneumoniae causes a relatively mild form of pneumonia, but the closely related Chlamydophila psittaci causes the serious infection psittacosis, with symptoms including severe pneumonia, joint pain, nosebleed, diarrhea, and conjunctivitis.
Legionella pneumophila also causes a serious and potentially fatal condition, legionellosis or Legionnaire's disease. Mycoplasma pneumoniae causes one of the less severe forms of stypical pneumonia and typically affects young people. Yersinia pestis, the same bacterium responsible for bubonic plague, causes pneumonic plague, a rare but very serious condition.
The antibiotic used to treat bacterial pneumonia is selected based on the specific bacterial pathogen involved. They are often delivered intravenously, especially in hospitalized patients. Patients with severe or advanced pneumonia may also be administered oxygen if they are having trouble breathing.