Atypical Pneumonia

Pneumonia is an infection of the lungs that can be caused by viruses, bacteria, and fungi. A common cause of bacterial pneumonia is Streptococcus pneumoniae. Other bacteria can cause pneumonia, including Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, and Legionella pneumophila. These bacteria are referred to as “atypical” because pneumonia caused by these organisms might have slightly different symptoms, appear different on a chest X-ray, or respond to different antibiotics than the typical bacteria that cause pneumonia. Even though these infections are called “atypical,” they are not uncommon.