Legionnaires' disease in children
Introduction
Introduction to Pediatric Legionnaires' Disease Legionnaires pneumonia (legionnaires'pneumonia) is caused by Gram-negative Legionella pneumoniae (Legionellapneumophila), which has been shown to be a novel pathogen and can cause pneumonia and Pontiac fever ( Pantiacfever) two infections. This new type of pneumonia has received widespread attention in the past decade or more. basic knowledge The proportion of illness: 0.23% Susceptible people: children Mode of infection: respiratory transmission Complications: pleural effusion, acute toxic encephalopathy in children, respiratory failure, lung abscess
Cause
Pediatric Legacy
(1) Causes of the disease
Legionella is a type of Gram-negative Aerobacter aeruginus requiring special nutrition. It is 0.3-0.9m wide and 23m long. It can not grow in ordinary medium. Generally, it uses Mullner-Hinton agar, Feeley-Gormall agar or CYE agar. The medium is cultured in 2.5% carbon dioxide and 35 ° C for 2 to 7 days. The cell wall contains a high proportion of short-branched fatty acids, which is rare in Gram-negative bacilli and is an important identification point. Legionella is associated with human diseases in six species, namely L. pneumophila, L. micdadei, L. dumoffii, L. gormanii and L. long-beachae, of which the first species, Legionella pneumophila, is most common. There are 10 serotypes. Legionella contains a variety of exotoxins and endotoxins. The combination of several toxins causes disease.
(two) pathogenesis
At present, the pathogenesis of Legionella pneumonia is still not very clear. Legionella pneumophila enters the lungs through the air. After the bacteria enter the lung tissue, the lesions are mainly located in the alveoli, from alveolar retrograde to respiratory bronchioles, and then to the larger bronchioles. A few extend to the interstitial or pleural, lymphatic, thoracic duct and blood circulation, into the blood circulation to the liver, spleen, kidney and central nervous system, etc., causing multiple organ damage, when Legionella enters the human body and is swallowed by monocytes Can not be inactivated, and continue to multiply in monocytes, neutrophils and monocytes can kill Legionella outside the phagocytic cells with the participation of specific antibody C3, late stage of Legionella infection, due to neutrophils And monocytes rapidly increase, other cell chemokines and specific antibodies are formed, so that bacterial growth is inhibited. When serum antibodies reach a peak, Legionella is eliminated, pathological changes: focal nodular lesions or fusion Bronchial pneumonia can progress to lobar pneumonia, 25% of cases have small abscesses, severe cases have serous or serous pleural effusion, microscopically, lung And respiratory bronchioles next to severe inflammation, alveolar epithelial cell loss, how thick neutrophils, macrophages and cellulose exudate, less affected large airways and alveoli alveolar septum.
Prevention
Pediatric Legionnaires' Disease Prevention
At present, there is no vaccine against Legionnaires' disease, which can only be controlled by early detection, early treatment and prevention-based comprehensive measures.
1. Precautions against environmental factors
Focus on cooling towers, water pipes and other fixed facilities that may lead to the proliferation and spread of Legionella, in the design, maintenance and management, the corresponding implementation methods for easy disinfection and cleaning, followed by the health sector to strengthen the soil in the region Animals' Legionella monitoring work, focusing on strengthening water source monitoring and management, cooling towers should be drained when not in use, regular mechanical cleaning, removal of scale, disinfection water supply system methods are: increase water temperature (60 ° C), regular water supply Pipes, disinfected with chlorine disinfectants.
2. Regular inspection
Hospitals, hotels, dance halls, cinemas, offices, etc., the water network, air conditioning, cooling tower water regularly check the contamination of Legionella, once the pollution is found, disinfection is immediately carried out.
3. Regular cleaning
For air conditioners used in homes, air filters, household hot water pipes, showers, heaters, etc., where water bodies may remain, are often cleaned.
4. Regular ventilation
In the confined space where the air conditioner is used, the indoor air must pay attention to the regular window ventilation, and the window must not always be sealed.
5. Strengthen health care
Exercise, improve the body's resistance, protect vulnerable populations, old or infirm as few as possible to the crowds, air-poor public places and other general protective measures, the current prevention and control of Legionella disease should be comprehensive preventive measures.
Complication
Pediatric Legionnaires Complications Complications pleural effusion children acute toxic encephalopathy respiratory failure lung abscess
Pleural effusion, toxic encephalopathy, respiratory failure, a small number of respiratory distress syndrome, shock, acute renal failure, lung abscess, DIC, etc. After 1 to 2 days, it showed high fever, dry cough (or cough), difficulty breathing, shortness of breath, chills, occasional diarrhea, and x-ray films showed signs of pneumonia. In severe cases, extrapulmonary signs can occur, which can be manifested as liver damage and renal failure. There are proteins and red blood cells in the urine, and some even have mental disorders. Some can also cause infective endocarditis, lung abscesses and even lungs. Empty and so on. And there is a certain mortality rate.
Symptom
Pediatric Legion Disease Symptoms Common Symptoms Voice pleural effusion high fever lethargy muscle pain diarrhea dyspnea coma respiratory failure lung consolidation
There are two basic types of diseases caused by Legionella pneumophila; non-pneumonia type is Pontiac fever, pneumonia type is called Legionella pneumonia or commonly known as Legionnaires' disease, Legionella pneumonia is a serious multi-system damaging disease, mainly It is characterized by pneumonia and fever. The incubation period is 2 to 10 days, with an average of 4 days. The main manifestations are fever, cough, cough, dyspnea, headache, myalgia, etc. Some children have mental disorders, and children are more acute than adults. Progress is faster, and some soon develop into respiratory failure, lethargy, coma, high mortality, often in the early stage, the lungs are scattered in the wet voice, 20% to 60% have a small amount of pleural effusion, and then most patients show pulmonary Metamorphosis, about 1/3 of the relative heart rate is slow, is one of the characteristics of this disease.
Examine
Pediatric Legionnaires' Disease Check
1. Routine and biochemical tests
Most of the children have white blood cells >10×109/L, neutrophil nucleus left shift, poor prognosis of leukopenia, proteinuria, microscopic hematuria, abnormal liver function, hyponatremia is also one of the characteristics of this disease, ESR Increased degree, cerebrospinal fluid examination is often negative, a small number of pressure increased, monocytes rose to (25 ~ 100) × 106 / L.
2. Special laboratory inspection
(1) Pathogen inspection
It is difficult to culture pathogens from secretions, blood, sputum, pleural effusion, etc., the positive rate is not high, and the culture takes more than 1 week, so it is difficult to make a diagnosis in time. If the specimen to be tested is sputum, it needs to be in the medium. Sino-plus polymyxin, vancomycin, etc., and acidified sputum, can increase the positive rate, of which the highest rate of tracheal aspiration culture, the positive results can confirm the disease, the current use of BCYE medium.
(2) Detection of bacteria and their antigens
1 Direct fluorescent antibody staining (DFA): the specificity is up to 94%, but the sensitivity is about 40%, and the results can be obtained within 2 hours, which is beneficial for early diagnosis.
2 Gene probe technology for detecting microorganisms in specimens: The method of detecting and identifying Legionella at the genetic level by using nucleic acid hybridization technology has been widely recognized. The probe method is relatively fast, but the technical requirements are high, and its specificity is currently controversial. Further research using polymerase chain reaction (PCR) is currently underway.
3 enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA): detection of urine antigens in Legionella pneumophila, suitable for early diagnosis of Legionella Legionella type I Legionella pneumonia, detection rate is high, up to 80 %, specificity is also strong, the most widely used.
(3) Serum specific antibody detection
The specific IgM antibody can be detected about 1 week after infection, and the IgG antibody starts to rise in about 2 weeks. The blood indirect fluorescence method (IFA) is the most widely used method in China, and the microagglutination test (mAA) can also be used for convective immunoelectrophoresis. Test (CIF), serum antibody determination has two problems in the diagnosis of Legionella. One is that the antibody can exist for several months to three years after the disease, so the serum antibody positive is difficult to distinguish whether it is a disease or a disease now, followed by a cross. The presence of antibodies, such as Chlamydia psittaci, Pseudomonas, Proteus, Escherichia coli, Staphylococcus aureus, Mycobacterium tuberculosis, Mycoplasma infection, cross-antibodies with Legionella, X-ray chest initially showing patchy Nodular infiltration shadow, often manifested as subarachnoid alveolar consolidation or alveolar-interstitial mixed lesions, usually unilateral localization, and later developed bilateral diffuse pneumonia, about half of which have pleural effusion, Others need to do B-ultrasound, electrocardiogram, EEG and other tests according to the condition.
Diagnosis
Diagnosis and diagnosis of pediatric legion disease
diagnosis
It is difficult to make a diagnosis in time based on clinical manifestations. The diagnosis needs to rely on laboratory tests:
1. Pathogen isolation: Legionella isolated from respiratory secretions, pleural effusion, blood or lung tissue is the most powerful diagnostic evidence.
2. Antigen detection: The methods include direct immunofluorescence (DFA), latex agglutination, radioimmunoassay, ELISA, etc. The most commonly used method is DFA.
3. Serological examination: The most commonly used indirect immunofluorescence method (IFA) is used to determine the serum antibody titer of children. In the recovery period, the double serum is increased by 4 times or more compared with the acute phase, reaching 1:128, or a single recovery period serum. The titer is 1:256 to confirm the diagnosis. This method is mainly used for retrospective diagnosis. The serum antibody is also determined by ELISA. The IgG antibody titer 1:160 has diagnostic significance. This method is suitable for epidemiological investigation.
4. Lack of specificity: The clinical manifestations of this disease lack specificity, but the following cases are highly suspected of this disease, for diagnosis:
(1) Epidemiology, pneumonia occurs collectively, and is related to hospitals or nurseries with air conditioning and hot and cold water systems.
(2) Pneumonia continues to be hot and relatively slow, with no symptoms at the beginning of the disease, relatively few respiratory symptoms, and more symptoms of the nervous system.
(3) Pneumonia with watery diarrhea, abnormal liver and kidney function.
(4) There are a large number of neutrophils on the smears of respiratory secretions, but bacteria are rarely found by Gram staining, and the common bacteria culture is negative.
(5) Ineffective for the treatment of penicillins, cephalosporins and aminoglycoside antibiotics.
5. Diagnosis
(1) respiratory secretions, sputum, blood or pleural effusion cultured in a special medium with Legionella growth; or direct secretion of respiratory secretions positive by fluorescence; or two indirect immunofluorescence (IFA) before and after antibody titer Increased by 4 or more times up to 1:128 or above.
(2) The antibody titer was increased by 4 times or more before and after the blood tube agglutination test (TAT) test, reaching 1:160 or above.
(3) Two times before and after the blood microagglutination test (MAA), the antibody titer increased by 4 times or more, reaching 1:64 or above, such as single IFA>1:256, TAT>1:320, combined with clinical X-ray May consider Legionella pneumonia.
Differential diagnosis
Legionella pneumonia should be differentiated from mycoplasmal pneumonia and influenza virus pneumonia.
(1) respiratory secretions, sputum, blood or pleural effusion cultured in a special medium with Legionella growth; or direct secretion of respiratory secretions positive by fluorescence; or two indirect immunofluorescence (IFA) before and after antibody titer Increased by 4 times or more. Up to 1:128 or above.
(2) The antibody titer was increased by 4 times or more before and after the blood tube agglutination test (TAT) test, reaching 1:160 or above.
(3) Two times before and after the blood microagglutination test (MAA), the antibody titer increased by 4 times or more, reaching 1:64 or above, such as single IFA>1:256, TAT>1:320, combined with clinical X-ray May consider Legionella pneumonia.
