At the end of 1930, a group of pneumonias with insignificant symptoms (X-ray confirmed) were clinically found to be called atypical pneumonia, which was distinguished from high fever, chest pain, and typical pneumonia with obvious signs of lung consolidation. Moreover, the pathogens of this group of atypical pneumonia were mainly Mycoplasma pneumoniae and some Legionella or viruses
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Until September 2012, when the SARS virus broke out and the new SARS was named Middle East Respiratory Syndrome, there is an in-depth discussion on epidemiology, symptoms, laboratory tests and treatment.
Author: Liang Shaochun, Hong Yong, Pan Hui
This article is published by the author with the authorization of Medical Pulse, please do not reprint it without authorization.
I. Epidemiology
01 Mycoplasma pneumoniae pneumoniae
Generally occurs in autumn and winter, children and young people are prone to occur, < 5 years old or > 65 years old people are relatively rare, almost every four years there is an epidemic, Mycoplasma pneumoniae size is between bacteria and viruses, is currently known to be able to live independently of the smallest microorganism, most of the infected population (dominant onset), a small number of Mycoplasma pneumoniae carrying state, is an important source of infection, 4-10 years after 62% can have a second onset, so its immunity after infection is non-persistent. Respiratory droplets are the main route of transmission. Among susceptible people, more than 60% of pneumonia in Canadian 4-20 years old, mycoplasma pneumonia is as high as 60%.
02 Middle East Acute Respiratory Syndrome pneumonia
Also known as severe acute respiratory syndrome (SARS) compared to other known coronaviruses, it is a completely new coronavirus that can survive in the blood for 15 days and can be transmitted by short-distance droplets and aerosols. Populations are generally susceptible, with clusters of diseases in families and hospitals. It is more common in young adults and has a relatively low rate of infection in children. In the United States, respiratory tract infections are caused by strains 229E and OC43 every 2-3 years, and mutant strains are 8-16 years. There is a 16-year interval between the new atypical in 2003 and the new topic pneumonia in 2019 to the present.
03 Chlamydia pneumonia
These include Chlamydia trachomatis and Chlamydia psittaci. It occurs throughout the year, has no sex differences, and is more common in school-age children. In a semi-enclosed environment. Such as homes, schools, the military, and other densely populated work areas can be endemic to a small extent. Chlamydia is an obligate intracellular bacterial-like parasite that is transmitted from person to person.
Chlamydia psittaci is found in the blood, liver, spleen secretions and feathers of infected birds, and the pathogens of bird droppings and feathers can also be infected by inhalation. Epidemiological investigation: Parrot and pigeon breeders, poultry processing plant workers, zoo workers, pet shopkeepers all have access to infection. The author found that there are chlamydia pneumonia pathogens in the wax museum environment and the phenomenon of infection.
04 Legionella pneumonia
In 1976, the American Veterans Association rallied in Philadelphia and there was an epidemic of pneumonia, a gram-negative bacillus without capsular membranes that can cause outbreaks, sporadic and in-hospital epidemics in three ways. The incidence is higher in summer. The bacteria are suitable for air-conditioned environments and places where water supply systems are convenient. For the first time, the author confirmed that the bacterium can be found on the air conditioner and caused an epidemic. Male patients are 3 times higher than females. Studies have confirmed that less than 1% of the respiratory infections in the outpatient survey, and ICU severe pneumonia Legionella pneumonia accounted for 25%, ranking second. People with chronic cardiopulmonary diseases or malignant tumors, diabetes and other decreased immune function of the body are prone to lung infections with mixed microorganisms, resulting in the occurrence of "refractory pneumonia". In patients with leukemia and AIDS, the chance of hemoptysis caused by the bacteria increases.
2. Clinical manifestations
X-rays are generally required in this group of patients for early diagnosis, and are collectively referred to as atypical pneumonia due to atypical early symptoms and signs. There are generally no symptoms of chills, high fever, chest pain, and signs of lung consolidation, such as dull lung percussion, bronchial breath sounds, diplodges, and voice tremors are atypical.
Among them, cough and sputum production are the most common symptoms, which are difficult to distinguish from upper respiratory tract infections, but bronchial infections generally cough up sputum in the morning and lie down at night for 1-2 hours. Sputum production from pneumonia is not associated with postural changes. Fever in Mycoplasma and Chlamydia pneumonia rarely exceeds 38.5 °C, while coronavirus and Legionella pneumonia are usually irregularly high-fever, especially in the afternoon and at night. Chest pain is less than 10% and less pronounced than typical lobar pneumonia. Dyspnea is rare unless it occurs in patients with chronic cardiopulmonary disease or in people with tumors or AIDS.
Literature statistics: the incidence of atypical pneumonia pulmonary claudication is less than 10%, tubular breath sounds (bronchial breath sounds) are 3.5%, wet rales are 33%, and local voice tremors are enhanced by 18%.
In addition: Mycoplasma pneumoniae pneumonia occurs in 55% of adults with headache and is most prominent in the afternoon, associated with an increase in the condensation hormone of the bacteria. Dry cough is common. Moderate and low-grade fever, dry cough, headache as a "triple sign" of the pneumonia. Coronavirus pneumonia is dominated by white viscous sputum, often accompanied by local muscle spontaneous pain and tenderness. Mild pharyngeal hyperemia without local lymphadenopathy is one of the characteristics of the disease. In addition to pulmonary symptoms, chlamydia pneumonia is often accompanied by nosebleeds or a macule rash that appears 3 to 4 days after the onset of the disease. Legionella pneumonia is most common with gastrointestinal symptoms. Symptoms such as nausea, vomiting, and diarrhea are often present. If there is immunodeficiency in people with immunodeficiency, a variety of extrapulmonary manifestations can occur: cellulitis, sinusitis, and even peri-rectal abscesses, pericarditis, pyelonephritis, such as left pneumonia can be combined with acute pancreatitis, amylase elevation or endocarditis has a volatile murmur or small emboli shedding causes splenomegaly, subcutaneous hemorrhage.
Third, the value of laboratory tests and diagnosis
01 Blood routine
In 90% of patients with Mycoplasma pneumoniae pneumoniae, leukocytes are normal, but neutrophils are generally in the middle of 80% to 90%, with mild elevation. Coronavirus mild to moderate infection, almost all white blood cells decline, the proportion of lymphocytes is greater than 40%, because now the blood routine is no longer using staining classification, but instead of mechanical automated determination, it is classified according to the size of the cell, often some large lymphocytes are divided into monocytes, so monocyte pseudo-elevation occurs. In severe coronavirus infection, white blood cells and neutrophils are significantly elevated, a bit like bacterial pneumonia. Cells for chlamydia pneumonia are mostly normal. About 15% of chlamydia pneumonia can be accompanied by mild microcytic positive pigment anemia, legionella pneumonia leukocytes and neutrophils are almost all elevated, and 1/3 of legionella pneumonia is accompanied by transient increase in platelet count.
02 Condensation test
It has been used as the gold standard for Mycoplasma pneumoniae infection, but generally does not occur until the 7th to 10th day of the course of the disease, and the positive rate is highest at 4 °C at room temperature. However, it is not suitable for early diagnosis.
03 Mycoplasma-specific nucleic acid determination
By collecting sputum or serum from patients, the onset of the disease can be positive within 2-3 days, and there is no false positive or false negative.
04 Coronavirus pneumonia
D&D of pharynx and sputum or serum nucleic acid can occur positive within 1-2 days.
05 Chlamydia pneumoniae determination
Both local secretion nucleic acid assays or serum antibody assays can confirm the diagnosis, but the former is not yet widespread, and the latter can only reflect the disease after 7-10 days.
06 Legionella pneumonia
Serum antibodies can be positive for IgM about a week after infection, while IgG is produced later, rises after 2 weeks, and peaks at about 4 weeks. The bacterial nucleic acid determination can be determined by secretions and serum, and the positive reaction is 2-3 days after the onset of the disease.
07 Imaging studies
CT is more sensitive than ordinary chest x-ray, but solid exudation of alveoli can be found 2 to 3 days after the onset of the disease. However, the specificity is not high, and the change of inflammatory absorption is later than the decrease in body temperature and the absorption of luo yin. As with sputum production, it takes 3-4 weeks to disappear.
Mycoplasma pneumonia is segmental, rarely completely solid, and often has mixed normal alveolar translucency in the alveolar consolidation area. Typical pneumonia may extend outward from the hilars. Haze-like shadows are an important differentiator from bacterial pneumonia. Mycoplasma pneumoniae 15% can be combined with a pleural effusion in small amounts.
The shadow progression of coronavirus pneumonia changes rapidly, dominated by interstitial pneumonia, often in a butterfly-like distribution, grid-like shadow. In severe cases, diffuse, nodular infiltrates may be seen in both lower lungs with little to no pleural effusion.
Chlamydia pneumonia is more common in infiltrative shadows on one or both sides of the lower lung, which may be gridded or with changes in interstitial pneumonia or bronchopneumonia. The pneumonia does not present with pulmonary cavities and pleural effusions. Another feature is that it changes most slowly of all atypical pneumonia. Legionella lung early flaky infiltrative shadow, dominated by the middle and lower lung field. 50% involve both lungs, and cavities are rare. 25% with a small amount of pleural effusion. The range of inflammation in the lungs found on X-rays is inconsistent with clinical examination. X-ray lesion absorption begins only one week after clinical symptoms improve, with complete absorption 1-4 months.
4. Treatment
01 Mycoplasma pneumonia
Insensitive to penicillin and cephalosporins, macrolides are preferred, including fourteen macrolide structures of erythromycin, bermomycin and roxithromycin, clarithromycin, fifteen macrocyclic compounds azithromycin, sixteen, macrocyclic structures of metamycin, crosamycin, spiramycin. Taking azithromycin as an example, in order to prevent adverse reactions such as liver damage that may be caused by continuous medication, it is recommended to use three days of suspension for four days, and then use three days of intermittent therapy, and the following is a comparison of the efficacy of various drugs to kill Mycoplasma in recent decades.
Table 1 Comparison of drug efficacy is reported in the literature
02 Coronavirus infection
Drugs that inhibit viral adsorption (dimidamo) ion channel blockers (amantadine) inhibit viral protease synthesis (ribavirin) and neuraminidase inhibitors (drugs such as oseltamivir (Tamiflu)) are currently recommended.
Table 2 Efficacy of various drugs on coronavirus
Tetracycline is the first choice for treatment, macrolide antibiotics are also very effective, and quinolones (banned in pregnant children) can also be considered in young adults, and macrolides can be used intermittently (4-3-3) per course of treatment for 7 to 14 days.
Table 3 Inhibitory effects of various drugs on Legionella
5. Conclusion
The manifestations of all kinds of atypical pneumonia vary widely, but better results can be achieved by removing the source of infection, protecting susceptible people, and preventing and treating classic infectious diseases from the source, early diagnosis, and early treatment.
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