Overview of Chlamydia pneumoniae
Chlamydia pneumoniae is an infectious disease caused by Chlamydia pneumoniae, which mainly causes atypical pneumonia in adults and adolescents, and also causes acute respiratory infections such as bronchitis, pharyngitis and tonsillitis. Chlamydia pneumoniae is the third most common cause of community-acquired pneumonia after pneumococcus and Haemophilus influenzae. The rate of positive serum antibodies to Chlamydia pneumoniae is 54.8% in patients with respiratory infections and 24.8% in those with severe infections.
Etiology
Chlamydia pneumoniae is the causative agent of the disease, and was first isolated by Grayston in 1965 in the conjunctival secretions of a child in Taiwan, China, as a strain of Chlamydia different from other Chlamydia, named TW (Taiwan)-183 at that time, and in 1983 in the pharyngeal secretions of a college student with acute respiratory infection in Seattle, USA, as a strain of Chlamydia, named AR-39 (acuterespiratory syndrome), and in the same year, the strain of Chlamydia was also isolated. 39 (acuterespiratory-39) After research and identification, it was found that these two strains were actually the same chlamydia, and in 1989, it was officially named TWAR, also known as Chlamydia pneumoniae.
Symptoms
1. Acute respiratory infection
Acute respiratory infections are the main manifestations, such as pharyngitis, laryngitis, sinusitis, otitis media, bronchitis and pneumonia, with pneumonia being the most common and bronchitis the second most common. Pneumonia is most common in the elderly, and adolescents under 20 years of age are more likely to have bronchitis and upper respiratory tract infections. Often start with fever, generalized discomfort, sore throat and hoarseness, and then cough for a few days, at which time the body temperature is mostly normal. Can also cause bronchitis, bronchial asthma, the original bronchial asthma patients infected with Chlamydia pneumoniae, can aggravate the condition. Severe cases may be aggravated by the original underlying disease or die due to complications such as bacterial infection.
2. Typhoid type
A small number of patients show high fever, headache, relatively slow pulse and hepatosplenomegaly, easily complicated by myocarditis, endocarditis and meningitis, and severe patients have coma and acute renal failure, similar to severe typhoid fever.
3. Other
It can cause iritis, hepatitis, endocarditis, meningitis and erythema nodosum. It is an important cause of secondary infection in diseases such as AIDS, malignant tumor or leukemia. In recent years, Chlamydia pneumoniae infection has been found to be common in COPD. And the rate of Chlamydia pneumoniae-specific antibody positivity was found to be significantly higher in COPD patients than in the healthy population. In particular, more than 4% of acute exacerbations in COPD patients >50 years of age are associated with Chlamydia pneumoniae infection.
Tests
1. Laboratory tests
(1) Blood white blood cell counts are mostly normal, but may be elevated in severe cases. Blood sedimentation rate is often increased.
(2) Pathologic examination is a reliable method to confirm the diagnosis of the disease.
(3) Micro immunofluorescence test (MIF) is the international standard and the most commonly used serological diagnostic method of Chlamydia pneumoniae. Except for STD clinic patients and specific groups of prostitutes, the MIF serological diagnosis of Chlamydia pneumoniae can be made by using a single antigen of Chlamydia pneumoniae, i.e., it is not necessary to detect antibodies against Chlamydia trachomatis and Chlamydia psittaci at the same time. Serologic diagnostic criteria are: MIF test IgG ≥1:512 and/or IgM ≥1:32, after excluding false positives due to rheumatoid factor (RF), can be diagnosed as recent infection, double serum antibody titer 4-fold or more elevated is also diagnosed as a recent infection. 1:16 ≤IgG <1:512 is considered as previous infection.
(4) PCR method can detect the DNA of Chlamydia pneumoniae, which is more sensitive and can be distinguished from other species of Chlamydia.
2. Other auxiliary examinations
X-ray examination of lungs: atypical pneumonia manifestation, often unilateral stage pneumonia manifestation, severe cases of extensive lesions or even spread to both lungs, may be accompanied by pleurisy or pleural effusion.
Diagnosis
Since the disease lacks specific clinical manifestations, if the disease is suspected in patients with pneumonia or the above clinical manifestations, pathogenetic or immunologic tests can be done to confirm the diagnosis.
Differential diagnosis
This disease must be differentiated from other pathogen-induced pneumonias such as Mycoplasma pneumonia, viral pneumonia, Severe Acute Respiratory Syndrome (SARS), Legionnaires’ Disease, and other bacterial pneumonias, of which SARS is characterized by:
1. Epidemiological characteristics
Is a history of close contact with the onset of the disease, or is one of the infected group onset of the disease, or there is clear evidence of transmission to others. Or have visited or resided in an area where patients with the disease have been reported and secondary infection outbreaks have occurred within 2 weeks prior to the onset of the disease.
2. Clinical manifestations
The onset of the disease is rapid, with fever as the first symptom, body temperature > 38 ℃, may be accompanied by headache, joints, muscle aches and pains, cough with little sputum, chest tightness, and in severe cases, respiratory distress or respiratory distress, the lung signs are not obvious, and there may be a few wet rales or solid lesions in the lungs.
3. Blood test
Peripheral blood leukocytes and lymphocytes may be decreased.
4. Flaky, patchy or reticular changes in the lungs.
Others are mainly determined by the respective pathogenetic and/or serum immunologic tests.
Complications
Endocarditis, myocarditis, and meningitis may complicate.
Treatment
Chlamydia pneumoniae is extremely susceptible to tetracyclines, erythromycin, and fluoroquinolones, and is resistant to sulfonamides, so tetracycline or erythromycin is often given orally. Doxycycline can also be used. Tetracyclines and quinolones are contraindicated in pregnant and lactating women and children. Children can use clarithromycin (erythromycin) with good efficacy. Some cases may recur after stopping the drug, especially those treated with erythromycin, and then doxycycline treatment is still effective. In recent years, azithromycin, a new macrolide antibiotic, has been found to be highly sensitive to Chlamydia pneumoniae in the in vitro drug sensitivity test, which is easy to enter the cell, and has the advantages of high efficiency and low gastrointestinal reaction.
Prognosis
Most Chlamydia pneumoniae infections are asymptomatic or mild, with occult infections up to 90%. Occasionally, deaths are seen in the elderly and infirm.
Prevention
1. Take antibiotics reasonably to prevent the disease from prolonging and turning into chronic or long-term carrier.
2. Pay attention to collective and personal hygiene, and strengthen the management and supervision of environmental public health.