Chlamydia pneumoniae infection

Introduction to Chlamydia pneumoniae infection Chlamydiapneumonia infection (chlamydiapneumoniainfection) is an infectious disease caused by Chlamydia pneumoniae, which mainly causes atypical pneumonia in adults and adolescents, and can also cause acute respiratory infections such as bronchitis, pharyngitis and tonsillitis. The occurrence and prevalence of this disease is higher in the tropical countries than in the developed countries in the north. In some areas, the incidence of the 5-14 age group is higher than that of adults. basic knowledge The proportion of sickness: 0.0026% Susceptible population: the incidence of 5 to 14 years old is higher than that of adults Mode of infection: respiratory transmission Complications: Myocarditis Meningitis Endocarditis

Causes of Chlamydia pneumoniae infection

(1) Causes of the disease

The pathogen of this disease is Chlamydia pneumoniae. In 1965, Grayston first isolated a chlamydia different from other chlamydia in the conjunctival secretion of children in Taiwan, which was named TW (Taiwan)-183, and in 1983 in Seattle, USA. In the pharyngeal secretion of a college student with acute respiratory infection, another chlamydia was isolated and named as AR-39 (acute respiratory-39). After identification, the two strains were found to be the same chlamydia and inclusion bodies. The morphology is similar to that of Chlamydia psittaci, but its ultrastructure, monoclonal antibody reaction and DNA homology are different from Trachoma and Chlamydia psittaci. In 1989, it was officially named TWAR, also known as Chlamydia pneumoniae. The third type of chlamydia.

The morphology of Chlamydia pneumoniae is different from that of the other two chlamydia, but it is similar to Chlamydia psittaci, the inclusion body is densely oval, and it is not stained with glycogen iodine. The electron microscope is usually pear-shaped and may be pleomorphic. The average diameter is 380 nm, and the surrounding raw pulp area is larger; the starting body is spherical, and the average diameter is 510 nm.

The main outer membrane protein (MOMP) of Chlamydia pneumoniae is the main structural protein, the most important of which is heat shock protein (HSP), which is an important pathogenic substance, especially related to the formation of intimal injury and atherosclerosis. Currently known to have two serotypes.

Tissue culture is more difficult than other chlamydia, and Hela cells, 229 cells, HEP-2 (human laryngeal carcinoma) cells, Mc Coy cells and MTED (human tracheal epithelial) cells can be cultured, among which HEP-2 cells are most sensitive.

(two) pathogenesis

In view of the fact that the pathogens of this disease are not found for a long time, the pathogenesis is still unclear. After Chlamydia pneumoniae invades the human body, it mainly causes mononuclear macrophage reaction, and alveolar macrophages act as carriers for the storage and transmission of pathogens, causing their persistent infection in the host. In the study of experimental animals in non-human mammals such as mice and monkeys, it was found to be asymptomatic after infection, most of which showed pulmonary lesions after 2 months, mainly as interstitial pneumonia, and early localized multinucleated cell infiltration. In the future, macrophages and lymphocytes infiltrate, and Chlamydia pneumoniae can be isolated from the lungs and spleen. The infection is mostly chronic, so it is associated with many chronic infections, such as coronary heart disease, atherosclerosis, and chronic obstructive pulmonary disease ( COPD), bronchial wheezing, sarcoidosis and reactive arthritis.

Chlamydia pneumoniae infection prevention

1. Reasonably take effective antibiotics, and cure as soon as possible to prevent the disease from prolonging and turn into chronic or long-term bacteria.

2. Pay attention to collective and personal hygiene, and strengthen the management and supervision of environmental public health.

3. There is currently no vaccine.

Complications of Chlamydia pneumoniae infection Complications Myocarditis Meningitis Endocarditis

Can be complicated by frontal sinusitis, endocarditis, myocarditis, meningitis and so on.

Symptoms of Chlamydia pneumoniae infection Common symptoms Coma hoarse fever

The incubation period of this disease is 10 to 65 days, lacking specific clinical manifestations, asymptomatic infections and mild patients are common.

1. Acute respiratory infection is its main manifestations, such as pharyngitis, laryngitis, sinusitis, otitis media, bronchitis and pneumonia. The most common cause of pneumonia is more than 50%, followed by bronchitis, and the elderly are more common with pneumonia. The following young people are mostly bronchitis and upper respiratory tract infections, often with fever, general malaise, sore throat and hoarseness, and coughing occurs several days later. At this time, the body temperature is normal, and can also cause bronchitis and bronchial asthma. The original bronchial asthma patients infected with Chlamydia pneumoniae, can aggravate the condition, can also cause pharyngitis, sinusitis and otitis media, which is more common with pneumonia and bronchitis, the lesions are generally lighter, but even with antibiotic treatment, the disease recovers Symptoms such as slowness, cough, and general malaise can last for weeks to months, and severe cases can result from aggravation of the underlying disease or death from complications such as bacterial infection.

2. Typhoid type A small number of patients showed high fever, headache, relatively slow pulse and hepatosplenomegaly, easy to develop myocarditis, endocarditis and meningitis, severe cases of coma and acute renal failure, similar to severe typhoid.

3. Correlation between Chlamydia pneumoniae infection and atherosclerotic coronary heart disease and acute myocardial infarction According to statistics, 50% of patients with chronic coronary heart disease and 68% of patients with acute myocardial infarction can detect anti-Chlamydia pneumoniae antibodies (IgG and IgA). Only 17% of the control group were immunohistochemically stained with monoclonal antibodies against Chlamydia pneumoniae or by PCR. In the sclerotic plaques of coronary or aorta, Chlamydia pneumoniae antigen or its DNA was detected, confirming the presence of pathogens in the lesion. It was not detected in normal arterial tissues. It was also observed under electron microscopy that pears with similar size and morphology to Chlamydia pneumoniae were observed on the hardened coronary artery wall. Gloria et al. reported immunofluorescence with monoclonal antibodies, respectively. Chlamydia pneumoniae antigen was detected in arterial and coronary arteriosclerosis specimens, the positive rate was 13% and 79%, respectively, and the normal aorta was 4%. Therefore, Chlamydia pneumoniae infection is associated with the occurrence of arteriosclerosis, which is a risk factor for coronary heart disease. Patients with coronary heart disease should be aware of the exclusion of Chlamydia pneumoniae infection, and believe that prevention and treatment of Chlamydia pneumoniae infection may reduce the incidence of coronary heart disease, it is reported that Patients with cardiovascular disease such as atherosclerosis, coronary heart disease and peripheral arterial embolism are often infected with Chlamydia pneumoniae, treated with macrolide antibiotics such as roxithromycin, and after 2 to 7 years of follow-up, the heart can be significantly reduced. The progress of vascular disease, as well as coronary heart disease patients with renal failure, has a higher infection rate of Chlamydia pneumoniae and is more likely to promote the progression of cardiovascular disease.

4. Others can cause iritis, hepatitis, endocarditis, meningitis and nodular erythema. It is one of the important pathogens of secondary infections such as AIDS, malignant tumors or leukemia. It is also found in some diseases such as malignant tumors. , cerebrovascular disease, renal insufficiency, Parkinson's syndrome, cirrhosis and diabetes, can detect a higher positive rate of Chlamydia pneumoniae antibody, the exact relationship between the two is not clear, in recent years, found that Chlamydia pneumoniae infection Common in COPD (65%), patients with severe disease are higher, and the positive rate of specific antibodies against Chlamydia pneumoniae in COPD patients is significantly higher than that in healthy people, especially those with COPD >50 years old, more than 4% of acute attacks and Chlamydia pneumoniae infection related.

Due to the lack of specific clinical manifestations of this disease, patients with pneumonia or the above clinical manifestations, such as suspected and the disease, can be diagnosed by pathogenic or immunological tests.

Examination of Chlamydia pneumoniae infection

1. Blood picture The white blood cell count is normal, the severe cases can be elevated, and the blood sedimentation is increased.

2. Pathogen examination is a reliable method for the diagnosis of this disease, clinical diagnosis is not commonly used.

(1) Direct smear: After smear, staining with Giemsa or immunofluorescent monoclonal antibody to detect inclusion bodies and protoplasts of Chlamydia pneumoniae is simple, but the positive rate is low.

(2) Tissue culture method: Chicken embryo yolk sac inoculation has been used less because of the low positive rate. Cell culture method can be used to take throat swab or collect lower respiratory tract specimens, and use HEP-2 cells (laryngeal cancer cells) or Hela229 cells. After 24 hours of culture, staining with specific monoclonal antibodies against Chlamydia pneumoniae was used to detect specific inclusion bodies. The method was more complicated and the detection rate was lower than other Chlamydia.

3. Immunological examination is a commonly used diagnostic method.

(1) Direct immunofluorescence: staining with monoclonal antibody against Chlamydia pneumoniae and direct immunofluorescence assay for Chlamydia pneumoniae antigen is method sensitive, rapid and simple.

(2) Microimmunofluorescence (MIF) method: detection of Chlamydia pneumoniae antibody, specific IgM titer 1:16 and (or) IgG 1: 512 or double serum titer more than 4 times higher, can be diagnosed Acute infection, such as IgM 1:16 or IgG 1: 512, is a previous infection, the specific sensitivity of this method is high, and can be used to distinguish between primary infection and reinfection, is currently the most commonly used and most sensitive Serological methods, but to rule out the effects of rheumatoid factors in the blood circulation.

(3) Detection of complement-binding antibodies: acute titers can be diagnosed if the titer is 1:64 and/or the serum titers are more than 4 times higher, but it cannot be used for early diagnosis, and it cannot be distinguished as which chlamydia. infection.

4. PCR method Detection of Chlamydia pneumoniae DNA, the sensitivity is higher, and can be distinguished from other species of chlamydia, its specific sensitivity is higher than other methods, according to statistics, PCR detection rate is 50% to 55%, and direct immunization Fluorescence and smear methods are 24% to 27% and 6% to 10%, respectively. The detection of polymerase chain reaction (LCR) can further improve the sensitivity and detection rate, but it has not been used in clinical applications. The PCR-EIA method is a rapid and simple enzyme immunoassay that can improve the efficiency of PCR detection of Chlamydia pneumoniae DNA amplification, which is superior to the PCR method and is superior to the culture method.

X-ray examination of the lungs: atypical pneumonia, often manifested as unilateral stage pneumonia, severe lesions and even spread to both lungs, may be associated with pleurisy or pleural effusion.

Diagnosis and identification of Chlamydia pneumoniae infection

Differential diagnosis

The disease must be differentiated from pneumonia caused by other pathogens such as mycoplasmal pneumonia, viral pneumonia, severe acute respiratory syndrome (SARS), Legionnaires' disease and other bacterial pneumonia. The characteristics of SARS are:

1 Epidemiological characteristics are closely related to the onset of the disease, or one of the infected group, or have evidence of a clear infection, or have been or have lived in the report for 2 weeks before the onset of the disease And there is an area of secondary infection,

2 clinical manifestations of acute onset, with fever as the first symptom, body temperature >38 ° C, may be associated with headache, joints, muscle soreness, cough and less sputum, chest tightness, severe breathing difficulties or respiratory distress, lung signs are not obvious, There may be a little wet voice or lung consolidation.

3 peripheral blood leukocytes and lymphocytes can be reduced,

4 The lungs are flaky, patchy or reticular, and others are determined primarily by their respective pathogens and/or serum immunological tests.

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