Chlamydial Infections

C. trachomatis can cause infections in many organs of the body such the urethra, cervix, and rectum. It is primarily spread sexually and can also be transmitted from pregnant people to their infants. (See also Chlamydial and Other Nongonococcal Infections.)

C. trachomatis is the most commonly reported bacterial infection in the United States. STIs are infections that are passed from person to person through sexual contact. Safer sex practices are recommended to decrease risk of spreading C. trachomatis to other people. (See also Prevention of Chlamydia.)

When spread through sexual contact, C. trachomatis can cause the following infections:

• In women: Cervicitis, urethritis, and pelvic inflammatory disease

• In men: Urethritis and, less commonly, epididymitis

• In both: Infection of the rectum (proctitis), lymphogranuloma venereum, and reactive arthritis

Pregnant people who are infected with C. trachomatis can transmit the infection to their baby during childbirth, which can cause an eye infection (conjunctivitis) or lung infection (pneumonia) in the newborn. To prevent these infections in newborns, doctors screen and treat pregnant people who are at risk of infection with chlamydia. These measures have greatly reduced the number of newborn conjunctivitis and pneumonia infections in the United States. (See also Screening for Chlamydia.)

Certain strains of C. trachomatis cause an eye infection called trachoma. Trachoma is a prolonged infection of the conjunctiva (the thin membrane lining the surface of the eye and inside of the lids).

C. pneumoniae can cause the lung infection pneumonia. C. pneumoniae is spread from person to person when people with the infection cough or sneeze while in close contact with others who then breathe in droplets that contain the bacteria.

Many cases of pneumonia that develop outside of hospitals (that is, from spread within a community) may be caused by C. pneumoniae. C. pneumoniae infection poses a particular risk for people in nursing homes, schools, military camps, prisons, and other crowded conditions. C. pneumoniae may also be a trigger of reactive airway disease (a diagnosis that doctors give when they suspect a person has asthma but have not yet confirmed it) and acute bronchitis.

C. psittaci causes psittacosis, which is an uncommon type of pneumonia. Psittacosis is a rare infection.

C. psittaci is present in birds, including pet birds such as parrots, parakeets, and cockatiels, and poultry. Psittacosis can develop in pet owners, veterinarians, and workers in the poultry industry exposed to turkeys or ducks. People become infected if they inhale dust from the waste of infected birds.

People infected with C. psittaci may have a high fever, severe headache, muscle pain, and cough. In rare cases, people may have trouble breathing.

C. psittaci is suspected mainly in people who have had close contact with birds, typically pet birds such as parrots or parakeets, and also in veterinarians and workers in turkey and duck processing plants. Doctors confirm the diagnosis by doing blood tests to detect antibodies, and certain laboratories are equipped to do the polymerase chain reaction (PCR) technique. For PCR, a sample of blood is used. The PCR technique increases the amount of the bacteria’s DNA and thus enables doctors to identify the bacteria more rapidly.

Doctors treat people with psittacosis with antibiotics that are taken by mouth such as azithromycin, levofloxacin, moxifloxacin, and doxycycline. Doctors treat people with psittacosis with antibiotics that are taken by mouth such as azithromycin, levofloxacin, moxifloxacin, and doxycycline.Doxycycline is preferred in most cases. People who have a severe case of psittacosis, such as those who have severe pneumonia or respiratory failure, may be hospitalized and given antibiotics by vein (intravenously).