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Atypical pneumonia refers to pneumonia caused by certain bacteria - namely, Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae. While atypical pneumonias are commonly associated with milder forms of pneumonia, pneumonia due to Legionella, in particular, can be quite severe and lead to high mortality rates.
Atypical pneumonia is a pneumonia that does not respond to the usual antibiotic treatment. It can be caused by bacteria, in particular Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila and Bordatella pertussis, or viruses including influenza and coronaviruses. Normally, these infections are not as severe as typical pneumonia, but legionella causes legionnaire’s disease, which kills up to 50% of its victims if left untreated. The deadly SARS virus, which appeared only last year, is a new coronavirus that causes atypical pneumonia.
Atypical pneumonia due to Mycoplasma and Chlamydophila usually cause milder forms of pneumonia and are characterized by a more drawn out course of symptoms unlike other forms of pneumonia which can come on more quickly with more severe early symptoms. Mycoplasma pneumonia often affects younger people and may be associated with symptoms outside of the lungs (such as anemia and rashes), and neurological syndromes (such as meningitis, myelitis, and encephalitis). Severe forms of Mycoplasma pneumonia have been described in all age groups. Chlamydophila pneumonia occurs year round and accounts for 5-15% of all pneumonias. It is usually mild with a low mortality rate. In contrast, atypical pneumonia due to Legionella accounts for 2-6% of pneumonias and has a higher mortality rate. Elderly individuals, smokers, and people with chronic illnesses and weakened immune systems are at higher risk for this type of pneumonia. Contact with contaminated aerosol systems (like infected air conditioning systems) has also been associated with pneumonia due to Legionella
The incidence of atypical pneumonia is dependent on the patient and the patient’s environment. For instance, mycoplasma and chlamydia pneumonias are spread by close contact (i.e. military barracks or college dormitories). Other factors that predispose individuals to atypical pneumonias are chronic illnesses, especially respiratory illnesses (i.e. bronchitis, emphysema, COPD), and a history of smoking. Also, use of chronic immunosuppressants like steroids tend to make people more susceptible to infection.
The mainstay of treatment for atypical pneumonia is antibiotic therapy. In mild cases, treatment with oral antibiotics at home may be appropriate. Severe cases (especially common with pneumonia caused by Legionella) may require intravenous antibiotics and oxygen supplementation. Antibiotics with activity against these organisms include - erythromycin, azithromycin, clarithromycin, fluoroquinolones and their derivatives (such as levofloxacin), and tetracyclines (such as doxycycline).
Atypical Pneumonia Causes
Atypical Pneumonia Symptoms
Atypical Pneumonia Diagnosis and Treatment
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