Chlamydial pneumonia refers to one of several types of pneumonia that can be caused by a variety of the bacteria known as Chlamydia.

Pneumonia is an infection of the lungs. The air sacs (alveoli) and tissues of the lungs become swollen, and the alveoli may fill with pus or fluid. This prevents the lungs from taking in sufficient oxygen, which deprives the blood and the rest of the body's tissues of oxygen.

There are three major types of Chlamydia: Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis. Each of these has the potential to cause a type of pneumonia.

Chlamydia trachomatis is a major cause of sexually transmitted diseases (called nongonococcal urethritis and pelvic inflammatory disease). When a woman with an active chlamydial infection gives birth to a baby, the baby may aspirate (suck into his or her lungs) some of the mother's bacteria-laden secretions while passing...