Chlamydia pneumoniae

• Chlamydia pneumoniae is a type of bacteria that causes respiratory tract infections, such as pneumonia (lung infection).
• The bacteria cause illness by damaging the lining of the respiratory tract including the throat, windpipe, and lungs. Some people may become infected and have mild or no symptoms.

Chlamydia pneumoniae

Pathogenesis

C. pneumoniae cannot survive outside the host for very long. For this reason, the bacteria are usually transmitted from close person-to-person contact by respiratory droplets. C. pneumoniae can also infect people who touch surfaces contaminated with these droplets and then touch their nose or mouth.

In the past 20 years, researchers have linked a wide variety of diseases to C. pneumoniae infection including:

• Atherosclerotic cardiovascular disease
• Multiple sclerosis
• Asthma
• Age-related macular degeneration
• Alzheimer’s disease
• Chronic fatigue syndrome
• Chronic skin wounds

However, researchers have not been able to confirm a causal relationship between these diseases and C. pneumoniae infection.

Chlamydiae are Gram-negative bacteria

Clinical Features

Chlamydia pneumoniae infections can occur in the upper or lower respiratory tract. Clinical presentations can vary widely. The incubation period is generally between 3 to 4 weeks; however, studies have documented shorter times.

People with C. pneumoniae infection most commonly present with cough, fever, headache, malaise and can develop:

• Laryngitis
• Pharyngitis
• Coryza
• Pneumonia

After gradual illness onset, symptoms due to C. pneumoniae respiratory infection may continue over extended periods. Patients may experience a persistent cough and malaise for several weeks or months despite appropriate antibiotic therapy.

Clinical Complications

Most respiratory infections caused by C. pneumoniae are asymptomatic or mild, although severe complications can occur. These severe complications can result in hospitalization and sometimes death. Complications include:

• Exacerbation of asthma
• Encephalitis
• Myocarditis

People at Increased Risk

People of all ages can get sick from C. pneumoniae. It most commonly infects people for the first time when they are school-aged children or young adults. However, reinfection is most common in older adults.

People at increased risk include those who live or work in crowded settings where outbreaks most commonly occur8, such as:

• Schools
• College residence halls
• Military barracks
• Nursing homes
• Hospitals
• Prisons

Older adults are at increased risk for severe disease caused by C. pneumoniae infection, including pneumonia.

Signs and Symptoms

In general, Chlamydia pneumoniae infection is a mild illness that most commonly causes an upper respiratory tract infection. These upper respiratory tract infections can include a sore throat or an ear or sinus infection. Common symptoms include:

• Runny or stuffy nose
• Fatigue (feeling tired)
• Low-grade fever
• Hoarseness or loss of voice
• Sore throat
• Slowly worsening cough that can last for weeks or months
• Headache

C. pneumoniae can also cause lower respiratory tract infections like bronchitis and lung infections like pneumonia. Some reports say that people with pneumonia caused by C. pneumoniae are more likely to have laryngitis compared to people with other types of bacterial pneumonia.

Disease progression

It can take 3 to 4 weeks for symptoms to appear after someone has been exposed to the bacteria. Symptoms can also continue for several weeks after they start.

Diagnosis

• Laboratory test that involves taking a sample of sputum (phlegm) or swab from the nose or throat and blood tests including blood culture and sensitivity.
• Currently, there are multiple commercially available systems for the detection of C. pneumoniae infection, including several Food and Drug Administration (FDA)-cleared tests.
• Real-time Polymerase Chain Reaction (PCR) is the preferred method of diagnostic testing for acute C. pneumoniae infection, assuming the availability of an appropriate specimen type.

Treatment

Illness caused by Chlamydia pneumoniae is usually self-limiting and patients may not seek care. Clinicians can treat the disease on a case-by-case basis with:

• Macrolides (azithromycin) — first-line therapy
• Tetracyclines (tetracycline and doxycycline)
• Fluoroquionolones

Note: Clinicians should not prescribe tetracyclines for young children under normal circumstances.

C. pneumoniae shows in vitro resistance to the following antibiotics, which are not recommended for treatment:

• Penicillin
• Ampicillin
• Sulfa drugs

Symptoms of C. pneumoniae infection can reappear after a short or conventional course of antibiotics. Persistent infection after treatment has been demonstrated by recovery of viable bacteria; therefore, a secondary course of treatment may be recommended.

Complications

Most respiratory infections caused by C. pneumoniae are asymptomatic or mild, although severe complications can occur. These severe complications can result in hospitalization and sometimes death. Complications include:

• Exacerbation of asthma
• Encephalitis
• Myocarditis

Prevention

There is no vaccine to prevent Chlamydia pneumoniae infection, but there are steps you can take to help protect yourself.

Hygiene

Like many respiratory diseases, people are likely to spread C. pneumoniae by coughing and sneezing. To keep from getting or spreading the bacteria, wash your hands often. This is especially important after coughing or sneezing. To practice good hygiene, you should:

• Cover your mouth and nose with a tissue when you cough or sneeze.
• Put your used tissue in the waste basket.
• Cough or sneeze into your upper sleeve or elbow, not your hands, if you don’t have a tissue.
• Wash your hands often with soap and water for at least 20 seconds.
• Use an alcohol-based hand rub if soap and water are not available.