Haemophilus influenzae pneumonia in children

Introduction to pediatric Haemophilus influenzae pneumonia Hemophilus influenzae pneumonia (hemophilus influenzalpneumonia) is caused by Haemophilus influenzae, more common in infants under 4 years old, occasionally in newborns and adults, often complicated by influenza virus or staphylococcal infection, symptoms, signs and X-ray examination results are not easily distinguished from other bacterial pneumonia. basic knowledge The proportion of illness: the probability of illness in infants and young children 7% Susceptible people: children Mode of infection: droplet spread Complications: sepsis meningitis septic arthritis bronchodilation

Causes of childhood haemophilic influenza bacillus pneumonia

(1) Causes of the disease

The Haemophilus influenzae is a Gram-negative bacillus, which is divided into two types, capsular type and non-capsulated type. Non-capsulated strains generally do not have a type-specific capsular-type strain containing a capsular polysaccharide antigen. Application-specific immune sera can be divided into a type-v6 type with type b-type virulence and strongest clinically nearly 95% of severe Haemophilus influenzae infection is caused by type b. The younger the age, the greater the risk of infection with Hib, and the higher the incidence.

Bacterial infection (40%):

Hib is mainly transmitted through air droplets or contact secretions, and newborns can be infected through the mother's birth canal. Most of the infections are sporadic, and there are morbidity all year round, but it usually starts to rise in the fall, and the peak in winter is caused by the infection, and most of the respiratory tract infections. Genetic factors may have a more important role.

Low immunity (35%):

In addition, disease factors such as congenital immunodeficiency disease, congenital or functional splenomegaly, premature delivery, malnutrition, etc. can increase the risk of Hib infection. In recent years, Hib infection has increased due to the long-term application of immunosuppressive drugs and the increase of tracheal intubation in children with leukemia or other malignant lymphomas due to the use of a large number of broad-spectrum antibiotics.

(two) pathogenesis

The most vulnerable people are infants and young children, the elderly, and those with low immune function (tumor, diabetes, etc.), who often develop systemic infections such as Haemophilus pneumoniae and sepsis.

Pathogenic mechanism

Haemophilus influenzae adheres to the oral and nasopharyngeal epithelial cells through its filamentous fimbriae, secretes IgA protease, prevents SIgA from acting on it, and Haemophilus influenzae produces endotoxin-like lipid A component (lipopolysaccharide LOS). Glycoprotein-related factors, or low-molecular-weight glucopeptides, can inhibit epithelial cell cilia movement, so that Haemophilus influenzae is not excreted into the airway, and the capsular polysaccharide of type b strain has anti-phagocytosis, which makes Hib evade the elimination of host phagocytic cells. The effect is combined with the airway epithelial gland by filamentous fimbriae or adhesion factor. Haemophilus influenzae penetrates into the airway epithelial cell barrier and can grow locally and spread to adjacent tissues, causing respiratory diseases and invading blood. Flow causes sepsis, causing systemic disease, which can invade the central nervous system through blood, causing meningitis.

2. Immune response

The bactericidal antibodies to capsular antigens, complement, phagocytic cells and neutrophils play an important role in anti-infective immunity.

(1) Antibody: Local SIgA plays an important role in preventing Haemophilus influenzae from adhering to the respiratory mucosa. Anti-Hib capsular polysaccharide bactericidal antibody, anti-LOS antibody and anti-OMP antibody bind to bacteria, and its Fc segment binds to phagocytic cells. It has a conditioning effect on the phagocytic phagocytosis of phagocytic cells. The anti-capsular bactericidal antibody level induced by Haemophilus influenzae infection is lower in children <2 years old, higher in older children, high level anti-LOS antibody, anti- OMP antibodies help prevent the recurrence of Hib disease.

(2) Complement: Hib has the function of activating the classical pathway of complement and the alternative pathway. Complement promotes the bactericidal action of phagocytic cells through conditioning, and is mainly activated by alternative pathways in the early stage of infection, and relies on the role of classical pathways in the late stage of infection. In children with congenital complement deficiency, such as C2, C3, C4 or C3b inactivation factor deficiency, the susceptibility to Haemophilus influenzae infection is increased.

(3) phagocytic cells: neutrophils and mononuclear macrophages work together to eliminate Haemophilus influenzae, mainly in the body by the mononuclear-macrophage system, in children with splenectomy, bloodthirsty to the flu The susceptibility to bacillus infection is increased.

Childhood haemophilus influenza bacillus pneumonia prevention

In the autumn and winter seasons, attention should be paid to the prevention of Haemophilus influenzae infection, especially for children and the elderly and the infirm. During the epidemic, it is necessary to go to crowded places, pay attention to cold and warmth, and keep indoor air open.

1. Haemophilus influenza vaccine

Vaccination is the main measure to prevent infection. The Haemophilus influenzae type b capsular polysaccharide vaccine is the most widely used new type of coupled vaccine. The World Health Organization has confirmed the preventive effect and safety of this vaccine. Widely used in infant populations worldwide, Hib capsular polysaccharide vaccine (PRP) has been approved for use in the United States and has been shown to be safe and effective for children over 2 years of age. It should be noted that the ability to synthesize anti-PRP antibodies in infants is not perfect. After the initial infection with the blood-borne influenza bacillus, it may be re-infected for the second or third time. In addition, various Hib capsular polysaccharide protein vaccines such as PRP pertussis vaccine, PRP diphtheria tetanus pertussis combined vaccine (PRP-DTP) The PRP-diphtheria toxoid combination vaccine is under experimental and evaluation, and the purpose of the research is to improve the antibody reactivity of the body.

2. Antibiotics

Some authors suggest that taking rifampicin in contact with patients with Hib infection can prevent it. The dose is 20 mg/kg per day for 4 days, or intramuscular injection of gamma globulin or bacterial polysaccharide immunoglobulin (BPIG). Produces effective protection against infection of type B strains. For all children with invasive Hib infection, rifampicin should be taken before or after completion of antibiotic treatment, because the application of antibiotics does not completely confirm the bacteria in the nasopharynx. Clear.

Pediatric haemophilic influenza bacillus pneumonia Complications sepsis meningitis septic arthritis bronchodilation

Small infants with multiple empyema, pericarditis, sepsis, meningitis and septic arthritis, easy bronchiectasis.

Pediatric haemophilus influenza pneumonia symptoms common symptoms dyspnea sputum cough sputum vocal meningitis sepsis pericardial filling heart failure empyema pericarditis

The onset is slower, the course of the disease is subacute, and there is often a history of upper respiratory tract infection before onset, followed by fever, cough, cough, difficulty breathing, cyanosis and other symptoms. In addition, clinical manifestations of spastic cough and heavier Symptoms of systemic poisoning, physical examination can be seen bronchial pneumonia or signs of lung consolidation, can smell tubular breath sounds and wet voice, etc., easy to have empyema, meningitis, sepsis, pericarditis, etc., the course of disease for several weeks, severe heart failure Or pericardial tamponade, X-ray chest X-ray can be bronchial pneumonia, lobar pneumonia or consolidation of lung segments, about 20% of empyema, pneumonia can form lung bullae after absorption.

Examination of children with Haemophilus influenzae pneumonia

Blood picture

The white blood cell count can be reduced or increased to (20-70) × 10 ⁹ /L, and most of them are (1.5 ~ 2) × 10 ⁹ / L, accompanied by relative or absolute elevation of lymphocytes.

2. Pathogen examination

The most important laboratory test is the pathogen examination, which can take blood, pharyngeal secretions, sputum, cerebrospinal fluid, pleural effusion, pericardial fluid, joint fluid, tracheal aspirate and other specimens for smear to find bacteria, or with Levinthol stock solution. Special Hi medium for culture, Hib antiserum, -f multivalent antiserum can be used for further classification, sputum examination is the most commonly used method, generally requires 2 or more consecutive sputum culture results, flu The diagnosis of Haemophilus pneumonia depends on the culture of sputum. If the blood or pleural effusion culture is positive, it is more meaningful. The baby is not easy to cough up. The bronchial secretion can be sucked out by a sterile catheter for culture. Blood culture is very important for diagnosis. Through blood culture results, not only can we understand the existence of asepticemia, but also can estimate the prognosis. It is reported that the blood culture positive rate of Haemophilus influenzae is 60%, pleural effusion examination or pathological examination of lung puncture It also has diagnostic value. In addition, latex microagglutination (LPA) and convective immunoelectrophoresis (CIE) have been used for antigen detection of Haemophilus influenzae, contributing to Haemophilus influenzae. Rapid diagnosis of pneumonia.

3. Bacterial antigen examination

Because Haemophilus influenzae is a common flora of the upper respiratory tract, it is not advisable to use the nasopharyngeal specimen for antigen detection when diagnosing respiratory hibric infection. It can be checked with sinus puncture fluid, tracheobronchial fluid and bronchoalveolar lavage fluid. These specimens are difficult to obtain. Generally, blood and urine specimens are usually used for examination.

(1) capsular antigen: Hib secretes b-type polysaccharide capsule during growth. ELISA method, latex particle agglutination test, synergistic agglutination test, convection immunoelectrophoresis, etc. can be used to determine serum, cerebrospinal fluid, urine, pericardium, and joint fluid. In the specimens, the type b polysaccharide capsular antigen, in Hib meningitis, the positive rate of capsular antigen in cerebrospinal fluid was 90%.

(2) Outer membrane protein (OMP) antigen: The double-antibody sandwich ELISA method is used to determine the OMP antigen of Hib, and the application of two monoclonal antibodies (coated antibody and enzyme-labeled antibody) against different antigenic determinants can improve the examination. Sensitivity.

4. Serological testing

The type B polysaccharide capsule antibody can be determined by ELISA, the anti-Hib polysaccharide (Hib-PRP) antibody can be determined by radioimmunoassay, and the specific anti-OMP IgG, IgM of Hib can also be determined by indirect ELISA. The anti-OMP-IgM level is higher than the standard deviation of the same age by 2 standard deviations, or the double serum antibody is increased by 3 to 4 times or more to diagnose Hib infection.

5. Molecular biology examination

DNA molecular hybridization technique and PCR method were used to determine the specificity and sensitivity of Haemophilus influenzae DNA-specific fragments in clinical specimens. X-ray films may show bronchial pneumonia, lobar pneumonia or consolidation of lung segments. The lungs of the leaves are often affected, and may also be diffuse bronchopneumonia or bronchiolitis changes, often accompanied by pleural effusion, about 20% of empyema, pneumonia can form lung bullae after absorption.

Diagnosis and identification of children with Haemophilus influenzae pneumonia

According to clinical characteristics, symptoms and signs, combined with peripheral blood and chest X-ray examination, bacterial culture and virus isolation, or viral serology, immunofluorescence, enzyme-linked immunosorbent assay, hemagglutination inhibition test, etc., can determine the cause Diagnosis, the diagnosis of Haemophilus influenzae pneumonia depends on sputum culture.

Different from other pathogens caused by pediatric pneumonia, such as hemolytic streptococcus, Streptococcus pneumoniae and staphylococcus; viruses are pathogens of pneumonia, mainly RSV, adenovirus, parainfluenza virus, influenza A and B viruses, etc. Mainly rely on laboratory test results to identify.

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