Chlamydia family has only 1 genus, namely chlamydia, including four kinds of chlamydia, namely Chlamydia trachomatis and Chlamydia psittaci (C? Parrot fever), Chlamydia pneumoniae (C.pneumoniae) and Chlamydia pneumoniae (C. PE Corum). Objective: To explore the diagnosis and differential diagnosis of Chlamydia pneumoniae. Methods: The diagnosis was made according to the clinical manifestations and examination results. Conclusion: The clinical manifestations of Chlamydia pneumoniae pneumonia are not specific, and the diagnosis depends entirely on laboratory examination. The diagnosis of psittacosis pneumonia is mainly based on the relevant occupational history, contact history and cell culture of blood and bronchial secretions to find pathogens.
Keywords Chlamydia pneumoniae diagnosis
Chlamydia family has only 1 genus, namely chlamydia, including four kinds of chlamydia, namely Chlamydia trachomatis and Chlamydia psittaci (C? Parrot fever), Chlamydia pneumoniae (C.pneumoniae) and Chlamydia pneumoniae (C. PE Corum). Chlamydia trachomatis causes trachoma, inclusion conjunctivitis, nongonococcal urethritis and cervicitis. If the mother has genital chlamydia trachomatis infection, the fetus can be infected during delivery, which is manifested as neonatal chlamydia trachomatis pneumonia and inclusion body conjunctivitis. Chlamydia psittacosis causes human psittacosis, which manifests as respiratory tract infection or systemic infection mainly in respiratory system. Chlamydia bovis only infects cattle and sheep, and there are no reports of human illness. Chlamydia pneumoniae is a new species of chlamydia confirmed in recent years, and it is an important pathogen of pneumonia, bronchitis and sinusitis. Chlamydia pneumoniae pneumonia is usually mild, but it takes a long time to recover. Unlike psittacosis, patients infected with Chlamydia pneumoniae have no contact history with infected birds. Human infection caused by Chlamydia pneumoniae is far more common than other chlamydia species.
(1) Chlamydia pneumoniae pneumonia
1. Overview
Chlamydia pneumoniae is a newly named chlamydia, which mainly causes respiratory and lung infections.
2. epidemiology
Seroepidemiological investigation shows that human chlamydia pneumoniae infection is universal in the world. More than half of people in the United States and other parts of the world have been infected with Chlamydia pneumoniae, that is, there are specific IgG antibodies against Chlamydia pneumoniae in serum. Our study found that the infection rate of Chlamydia pneumoniae in China increased rapidly with age, and there was no gender difference. The infection rate of children is about 20%, which can reach 50% ~ 60% for young adults and 70% ~ 80% for the elderly. Considering the high positive rate of Chlamydia pneumoniae in the population and the decreasing antibody after infection, it is estimated that all people may be infected with Chlamydia pneumoniae at some time in their lives, and reinfection is also common. The annual incidence of Chlamydia pneumoniae in the age group of 5-9 years and the age group of 10 ~ 14 years were 9% and 6% respectively, which was the highest in the whole population. Chlamydia pneumoniae is strictly human chlamydia, and there is no animal intermediate host. The route of infection is through respiratory secretions and person-to-person transmission. There may be a local epidemic or a general epidemic in the work areas where families, schools, armies and other people are concentrated. Chlamydia pneumoniae infection spreads slowly, even in the densely populated areas mentioned above. Another study shows that chlamydia pneumoniae infection is not necessarily the source of infection, but asymptomatic carriers may be the source of infection. Chlamydia pneumoniae pneumonia accounts for about 5% ~ 10% of all community-acquired pneumonia.
Different from mycoplasma pneumoniae, chlamydia pneumoniae infection is mostly asymptomatic recessive infection or mild systemic infection, which has not attracted the attention of patients. Chlamydia pneumoniae pneumonia is more common in adults and elderly patients, but less common in adolescents under the age of 20.
3. Etiology
Chlamydia pneumoniae is a strict intracellular parasitic pathogen, gram-negative staining, parasitic in cytoplasm, producing inclusion bodies visible under light microscope. Different from virus, it has both DNA and RNA, and a cell wall similar to gram-negative bacteria, which is sensitive to broad-spectrum antibiotics.
Chlamydia pneumoniae (TW- 1983 in Washington, AR-39 1965 in Taiwan Province) is strictly a human pathogen, and there is no animal intermediate host. Seroepidemiological investigation shows that human chlamydia pneumoniae infection exists worldwide and is positively correlated with population density.
4. Clinical manifestations
Mild people can have no obvious symptoms. Teenagers often have hoarseness, dry cough, and sometimes symptoms of pharyngitis, sinusitis and bronchitis such as fever and sore throat, which can last for several weeks. Pneumonia is usually mild, which is very similar to the clinical manifestations of mycoplasma pneumoniae infection. Adult pneumonia can be very serious, especially in the elderly, and usually requires hospitalization.
Chlamydia pneumoniae pneumonia, as a kind of atypical pneumonia, its X-ray manifestations are similar to other atypical pneumonia, that is, consolidation sign of air cavity, ground glass shadow, reticular shadow, bronchopneumonia and small nodular shadow. HRCT (high resolution CT) images showed lobular shadows, glandular bubbles, air cavity consolidation and ground glass shadows with lobular distribution, while air cavity consolidation and bilateral lung lesions were more common in Chlamydia pneumoniae pneumonia. Chlamydia pneumoniae pneumonia is mainly interstitial pneumonia and focal pneumonia with irregular distribution. The difference is that Chlamydia pneumoniae pneumonia can be seen in scattered or small focal foam cell reactions.
5. Laboratory inspection
The count and classification of white blood cells in peripheral blood are normal, but the erythrocyte sedimentation rate in 80% patients is accelerated. Specific laboratory examination methods include cell culture, serology and PCR technology.
1) cell culture nasopharyngeal or retropharyngeal swabs, tracheal and bronchial aspirates, alveolar lavage fluid and other specimens can be used for chlamydia culture. Recently, it was reported that the isolation rate of Chlamydia pneumoniae was greatly improved in the samples treated with trypsin and/or sodium EDTA. Isolates can be identified by species-specific monoclonal antibodies against Chlamydia trachomatis and Chlamydia pneumoniae and species-specific monoclonal antibodies against Chlamydia pneumoniae.
HL cell line is the most sensitive to the growth of Chlamydia pneumoniae, and HEP-2 (human laryngeal epidermal carcinoma) is also reported to be sensitive to the growth of Chlamydia pneumoniae. Nasopharyngeal or retropharyngeal swab is the most commonly used specimen, and trachea, bronchial aspirate and bronchoalveolar lavage fluid are the most ideal specimens, because there are more pathogens in the specimens, and the results are more clinical. Sputum specimens are usually toxic to cell culture.
Just like collecting samples of mycoplasma pneumoniae, wipe off as many cells as possible with a cotton swab, because chlamydia is accompanied by cells. The cotton swab should be made of calcium alginate, polyester and polyester fiber, and the handle is made of plastic or aluminum. Wood or bamboo cotton swabs should not be used because they may contain potential chlamydia inhibitors. The transport fluid of the specimen is 2SP containing antibiotics (0.2mol/L sucrose phosphate buffer containing 10% inactivated fetal bovine serum). Specimens should be refrigerated at 4℃ after collection. If they cannot be inoculated within 24 hours, they should be stored at -70℃. The samples were inoculated into centrifugal culture tubes or plates, so that the chlamydia particles in the samples were squeezed and adsorbed to the cultured cells under the action of external physical force, thus improving the sensitivity. Inclusion bodies can be seen in positive samples within 72 ~ 96 hours after inoculation. Isolates can be identified by using species-specific monoclonal antibodies against Chlamydia pneumoniae and stained by indirect fluorescence or direct fluorescence. 2) Serological micro immunofluorescence test (MIF) is the most commonly used standard method for chlamydia serology in the world, and its sensitivity is much higher than that of complement fixation test (CF) with chlamydia specific antigen as antigen, and also better than that of enzyme immunoassay (EIA) based on lipopolysaccharide (LPS).
Serological diagnostic criteria: any chlamydia species, such as MIF test IgG ≥ 1: 5 12 and/or IgM ≥ 1: 32, can be diagnosed as a recent infection after excluding the false positive caused by rheumatoid factor (RF); When the titer of double serum antibody increases by 4 times or more, it is also diagnosed as recent infection. IgG ≥ 1: 16, but < 1: 5 12, IgM antibody was negative, suggesting that chlamydia pneumoniae had been infected in the past.
3)PCR detection PCR has been successfully applied to detect Chlamydia pneumoniae in samples, such as throat swab samples. Studies have shown that PCR technology is 25% more sensitive than traditional culture methods. In addition, the advantage of PCR is that it does not need live Chlamydia pneumoniae, so the death of Chlamydia caused by improper transportation or freezing does not affect the test results.
6. Diagnostic criteria
The clinical manifestations of Chlamydia pneumoniae pneumonia are not specific, and the diagnosis depends entirely on laboratory examination. Chlamydia pneumoniae was obtained by respiratory tract specimen culture; The diagnosis can be made if the serum antibody titer of Chlamydia pneumoniae changes more than 4 times (increasing or decreasing), and the antibody titer of Chlamydia pneumoniae (micro-immunofluorescence test) is ≥ 1: 32. Serum chlamydia pneumoniae IgG antibody titer ≥ 1: 5 12 or IgM antibody titer ≥ 1: 16 (micro immunofluorescence test) is significant, so chlamydia pneumoniae infection should be highly suspected.
7. Differential diagnosis
Chlamydia pneumoniae pneumonia is similar to mycoplasma pneumoniae pneumonia, Legionella pneumonia and some viral pneumonia, and the differential diagnosis basically depends on laboratory examination.
(2) psittacosis pneumonia
1. Overview
Psittacosis is caused by chlamydia psittacosis, a gram-negative and inactive pathogen. The pathogen has the characteristics of other chlamydia, and is an obligate intracellular parasite, which is parasitic in tissues, blood and feces of parrots and other birds (such as chickens, ducks, turkeys, pigeons, peacocks and finches). Contact with the above poultry or inhalation of bird droppings can cause disease; During the acute attack, it can occasionally cause interpersonal transmission through the respiratory tract. After infection, people can carry pathogens for up to ten years. Most of this disease is sporadic.
2. Physiology and Pathology
After inhalation, the pathogen enters the blood stream and reaches the liver and spleen mononuclear macrophages for reproduction, and then spreads to the lungs or other organs through the blood stream. Lung diseases often start from hilum and blood. Objective Inflammatory reaction spreads to the surrounding area, causing lobular and interstitial pneumonia, especially the drooping parts of lung lobes or segments. The bronchioles and bronchial epithelium cause exfoliation and necrosis; Inflammatory cells and edema fluid oozed from alveoli, accompanied by a small amount of bleeding. In severe cases, lung tissue necrosis and hilar lymph node enlargement may occur, sometimes pleurisy reaction, local necrosis of liver and splenomegaly may occur, involving the heart, kidney, nervous system and digestive tract.
3. Clinical manifestations
The incubation period of the disease is 1 ~ 2 weeks, and the elderly can reach 4 weeks. The onset is more subtle. Symptoms may be like the flu. Severe pneumonia begins with chills and fever, and the temperature gradually rises above 40℃, accompanied by a relatively slow pulse. The patient feels weak, myalgia, joint pain, nose or macula, and cough occurs around 1 week, accompanied by a small amount of sputum or blood in sputum. In addition, patients can also have digestive tract symptoms such as nausea, vomiting and abdominal pain, as well as mental symptoms such as lethargy, delirium, numbness and convulsions, especially in children. In severe cases, there may be signs of consolidation, and occasionally hepatosplenomegaly. X-ray signs showed that the infiltrative foci of the two lungs radiated outward from the hilum, and the foci could be fused and distributed in a leaf shape, with more lower lobes. There are often diffuse bronchopneumonia or interstitial pneumonia, and sometimes miliary or obvious consolidation or a small amount of pleural effusion can be seen. White blood cell count is normal or slightly increased.
4. Diagnostic criteria
Mainly according to the relevant occupational history, contact history and blood and bronchial secretions to do cell culture to find pathogens for diagnosis. Although positive serum complement fixation test can not distinguish the types of chlamydia, it is still a simple diagnostic method if combined with contact history. If the titer of double serum antibody is increased by 4 times or the titer of single serum antibody is above 1: 64, it has diagnostic value. At present, direct immunofluorescence is used to detect monoclonal fluorescence samples, which has high sensitivity and specificity.
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