chlamydial pneumonia

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Related to chlamydial pneumonia: atypical pneumonia, Mycoplasma pneumoniae

Chlamydial Pneumonia



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


Pneumonia is an infection of the lungs. The air sacs (alveoli) and/or the 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.

Causes and symptoms

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 through the birth canal. This can cause a form of relatively mild pneumonia in the newborn, occurring about two to six weeks after delivery.
Chlamydia psittaci is a bacteria carried by many types of birds, including pigeons, canaries, parakeets, parrots, and some gulls. Humans acquire the bacteria through contact with dust from bird feathers, bird droppings, or from the bite of a bird carrying the bacteria. People who keep birds as pets or who work where birds are kept have the highest risk for this type of pneumonia. This pneumonia, called psittacosis, causes fever, cough, and the production of sputum containing pus. This type of pneumonia may be quite severe, and is usually more serious in older patients. The illness can last several weeks.
Chlamydia pneumoniae usually causes a type of relatively mild "walking pneumonia." Patients experience fever and cough. This type of pneumonia is called a "community-acquired pneumonia" because it is easily passed from one member of the community to another.


Laboratory tests indicating the presence of one of the strains of Chlamydia are sophisticated, expensive, and performed in only a few laboratories across the country. For this reason, doctors diagnose most cases of chlamydial pneumonia by performing a physical examination of the patient, and noting the presence of certain factors. For instance, if the mother of a baby sick with pneumonia is positive for a sexually transmitted disease caused by Chlamydia trachomatis, the diagnosis is obvious. History of exposure to birds in a patient sick with pneumonia suggests that Chlamydia psittaci may be the culprit. A mild pneumonia in an otherwise healthy person is likely to be a community-acquired walking pneumonia, such as that caused by Chlamydia pneumoniae.


Treatment varies depending on the specific type of Chlamydia causing the infection. A newborn with Chlamydia trachomatis improves rapidly with erythromycin. Chlamydia psittaci infection is treated with tetracycline, bed rest, oxygen supplementation, and codeine-containing cough preparations. Chlamydia pneumoniae infection is treated with erythromycin.


The prognosis is generally excellent for the newborn with Chlamydia trachomatis pneumonia. Chlamydia psittaci may linger, and severe cases have a death rate of as high as 30%. The elderly are hardest hit by this type of pneumonia. A young, healthy person with Chlamydia pneumoniae has an excellent prognosis. In the elderly, however, there is a 5-10% death rate from this infection.

Key terms

Alveoli — The small air sacs clustered at the ends of the bronchioles in the lungs, in which oxygen-carbon dioxide exchange takes place.
Aspiration — When solids or liquids that should be swallowed into the stomach are instead breathed into the respiratory system, or when substances from the outside environment are accidentally breathed into the lungs.
Sputum — Material produced within the alveoli in response to an infectious or inflammatory process.


Prevention of Chlamydia trachomatis pneumonia involves recognizing the symptoms of genital infection in the mother and treating her prior to delivery of her baby.
Chlamydia psittaci can be prevented by warning people who have birds as pets, or who work around birds, to be careful to avoid contact with the dust and droppings of these birds. Sick birds can be treated with an antibiotic in their feed. Because people can contract psittacosis from each other, a person sick with this infection should be kept in isolation, so as not to infect other people.
Chlamydia pneumoniae is difficult to prevent because it is spread by respiratory droplets from other sick people. Because people with this type of pneumonia do not always feel very sick, they often continue to attend school, go to work, and go to other public places. They then spread the bacteria in the tiny droplets that are released into the air during coughing. Therefore, this pneumonia is very difficult to prevent and often occurs in outbreaks within communities.



American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872.

chlamydial pneumonia

An atypical pneumonia caused by Chlamydia species, characterized clinically by cough, low-grade fever, sore throat, and malaise. A chest x-ray taken during the illness is more likely to show diffuse lung involvement than a lobar pneumonia.
See also: pneumonia