Haemophilus influenzae pneumonia
Introduction
Introduction to Haemophilus influenzae pneumonia Hemophilus influenzae pneumonia (hemophilus influenzapneumonia) is a lung inflammation caused by Haemophilus influenzae. It was thought to be rare in adults. It occurs mainly in infants from 6 months to 5 years old, often with purulent meningitis. The status of Haemophilus influenzae in adult pneumonia is clinically recognized. According to statistics, 10% to 20% of community-acquired pneumonia is caused by Haemophilus influenzae, and 33% to 65% of hospital pneumonia is first of all nasopharyngeal influenza. Endogenous inhalation of Haemophilus is used as an initial bacterium, secondary to infection by other Gram-negative bacilli. basic knowledge The proportion of the disease: the probability of the population is 0.0035% Susceptible people: no special people Mode of infection: respiratory transmission Complications: empyema
Cause
Haemophilus influenzae pneumonia
(1) Causes of the disease
Pathogenic bacteria infection (45%):
The Haemophilus influenzae is a Gram-negative bacillus, which is classified into capsular type 6. The type B is the most pathogenic, and nearly 95% of clinically serious Haemophilus influenzae infections are caused by type b. The younger the age, the greater the risk of infection with Hib, and the higher the incidence. 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 peaks in the winter. Among the infections caused by it, respiratory tract infections are mostly. Genetic factors may have a more important role.
Disease factors (20%):
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 application of a large number of broad-spectrum antibiotics, long-term use of immunosuppressive drugs in children with leukemia or other malignant lymphomas, and increased tracheal intubation.
As a Gram-negative bacillus, Haemophilus influenzae is about 1.5m×0.3m in size and has a rod-like shape and a filamentous shape. In acute infection specimens, it often appears in the form of B. brevis, and the bacteria in this group do not form spores. No flagella, can not exercise, some strains have polysaccharide capsules, the bacteria are aerobic bacteria, high nutritional requirements, need X and V growth factors, X factor is a hemoglobin present in hemoglobin, iron-containing Porphyrin, high temperature resistant, is a bacterial synthesis of peroxidase, catalase and cytochrome oxidase, these enzymes are important substances in the oxidation and reduction of bacteria to transfer electrons, V factor is a vitamin B substance The V factor contained in the blood is usually in a suppressed state, and the V factor can be released after being heated at 80 to 90 ° C for 10 minutes. Therefore, the influenza bacillus grows better on the chocolate medium, and after 24 hours of cultivation, the colony can be three kinds. Morphology: M type (mucus type), R type (rough type) and S type (smooth type), the colony of the capsulated strain is M type, sticky and shiny, strong toxic to human body, Haemophilus influenzae and Staphylococcus aureus in blood agar culture The satellite phenomenon can be seen when the nutrient is incubated together. Because Staphylococcus can synthesize the V factor, the Haemophilus influenzae colonies growing around the colony are larger, and the farther away is smaller. In addition, nicotine can promote the growth of Haemophilus influenzae.
Capsular Haemophilus influenzae contains capsular polysaccharide antigen, also known as M antigen, which is type-specific and can stimulate the body to produce protective antibodies. Serum-specific typing can be used for serological typing. Haemophilus influenzae is usually divided into two types. a ~ f 6 types, of which type b is the most pathogenic, its polysaccharide antigen contains ribose, polyribosvl-ribitol phosphate (PRP), can inhibit cell phagocytosis, clinically, Haemophilus influenzae type b The most common pneumonia is caused by f-type, and the non-capsulated strain is generally not pathogenic, but recent studies have shown that 25% of adults have antibodies to the capsular strain, and in patients with chronic obstructive pulmonary disease, there is no capsule. Type strains and Streptococcus pneumoniae often cause acute exacerbation of underlying diseases on the basis of acute upper respiratory viral infections. Until the 1960s, Haemophilus influenzae was generally sensitive to ampicillin. Since the first report on ampicillin resistant strains in the 1970s, The rate of drug resistance is rising, and there is a problem of resistance to multiple antibiotics. Different antibiotics have different resistance mechanisms.
(two) pathogenesis
The virulence of Haemophilus influenzae is related to a variety of virulence factors. In addition to endotoxin, Haemophilus influenzae can also produce histamine, shrink bronchial smooth muscle, secrete mucus, increase the permeability of epithelial cells, and destroy cilia. Exercise, pathogenic Haemophilus influenzae has IgA protease, which can hydrolyze secretory IgA of the respiratory mucosa and play a pathogenic role.
Normally, the colonized Haemophilus influenzae does not cause disease. The bacteria are excreted by the ciliary movement after inhalation of the trachea or bronchus from the oropharynx. At the same time, secretory IgA in the secretion of respiratory mucosa can protect the body from infection. However, when the body's resistance is reduced and the immune function is imperfect, it can cause infection, Haemophilus influenzae pneumonia, and even sepsis, purulent meningitis and life-threatening. This disease is easy to occur in infants from 6 months to 5 years old. This is related to the immune defense state of the body. Most breast-bred infants can obtain passive immunity against Haemophilus influenzae capsular polysaccharide antibody from the mother, but gradually weaken or even disappear with the baby's age. Because adults have improved immune systems and acquired protective antibodies after infection, it is rare for infants and older children less than 6 months old, and Haemophilus influenzae pneumonia is rare in recent years. The rate has increased, which may be related to the improvement of detection technology, the increase of drug-resistant strains and the change of bacterial virulence. The occurrence of pneumonia is also related to the lack of specific antibodies in patients, which is often associated with diabetes, nephrotic syndrome, gamma globulin deficiency, alcoholism or anti-tumor chemotherapy drugs, immunosuppressive drugs; in chronic obstructive pulmonary disease, In patients with cystic fibrosis and long-term smoking, Haemophilus influenzae is prone to invade the lower respiratory tract due to impaired local defense mechanisms.
The disease is often caused by tracheal-bronchial infection in infants and young children, developing suppurative bronchitis, bronchial epithelial cell necrosis, partial mucosal separation from the basement membrane, infiltration of bronchioles and surrounding lymphocytes and neutrophils, causing fine Bronchitis, bacteria invade the alveoli and grow in the alveoli, causing pulmonary telangiectasia, congestion, alveolar edema, exudation, enhanced neutrophil chemotactic phagocytic activity, accompanied by inflammatory exudate resulting in lung consolidation .
The lesions of adult patients are mostly bronchial pneumonia. The distribution of large leaves is not uncommon. The fusion of lesions can cause necrosis of lung tissue and even cavity, forming lung abscess, and extending into the pleura to form pleural effusion and empyema.
Prevention
Haemophilus influenzae pneumonia prevention
Haemophilus influenzae type b infection can stimulate the body to produce protective antibodies, but the duration is short, so the improvement of the vaccine has become an important issue in recent years. At present, the following vaccines are used:
1. Capsular polysaccharide vaccine (PRP) The vaccine has no protein component and is a hapten. It can stimulate the body to produce IgM antibodies, and can not stimulate the activation of helper T lymphocytes. Therefore, it does not amplify the immune and recall reactions, and has a short duration.
2. Polysaccharide-carrier protein-binding bacterin combines capsular polysaccharide antigen with carrier protein (usually diphtheria or tetanus toxoid) to enhance immunogenicity, strengthen the body's immune response, and have a long-lasting recall response. For infants and young children aged ~18 months, the effect is 80% to 90%.
3. The capsular oligosaccharide-variant diphtheria toxoid-binding bacterin is covalently bonded between the two, and it is currently considered to be strongly immunogenic and safe, with an efficiency of 97%.
Because nicotine is a nutrient component of Haemophilus influenzae, smoking cessation is one of the measures to prevent this disease in adults. Avoiding the abuse of antibiotics and preventing the emergence of drug-resistant strains is also an important preventive measure, especially for clinicians.
Complication
Haemophilus influenzae pneumonia complications Complications
Concurrent empyema.
Symptom
Haemophilus influenzae pneumonia symptoms Common symptoms Breathing sound low breath shortness of fever fever pleural effusion hairy pus
History of upper respiratory tract infection before onset, manifested as fever, cough, sputum purulent sputum, shortness of breath, cyanosis, similar to general pneumonia, low breath sounds, smelling wet voice, a few empyema, pleural effusion Signs.
Examine
Examination of Haemophilus influenzae pneumonia
Haemophilus influenzae pneumonia check item: serum adenosine deaminase, chest radiograph.
The adenosine deaminase (ADA) system is named adenosine aminohydrolase, which mainly catalyzes adenosine and deoxyadenosine, produces hypoxanthine and ammonia, and is one of the important enzymes for adenylate catabolism. ADA is widely distributed in various tissues of the human body, with the highest content of mucosa and spleen in the small intestine, followed by liver, kidney, bone and skeletal muscle. Intracellular ADA is mainly localized in the cytoplasm, and ADA activity in leukocytes is higher than that in red blood cells.
The total number of white blood cells is mostly increased, and serum adenosine deaminase (ADA) is increased. Serum adenosine deaminase normal value: 1 ~ 25U.
X-ray performance:
1 is usually the lung segment and the lung lobes.
2 showed bronchial pneumonia, manifested as patchy or multi-leaf infiltration, rarely formed lung abscess, about 20% of empyema occurred.
Diagnosis
Diagnosis and identification of Haemophilus influenzae pneumonia
diagnosis
Patients with susceptibility or risk factors with community-acquired pneumonia and early-onset ventilator-associated pneumonia in patients with mechanical ventilation of the tracheal intubation should be alert to Haemophilus influenzae pneumonia.
Differential diagnosis
Differential diagnosis should be differentiated from other pathogens, depending on the correct collection of specimens and selection of media.
1, staphylococcus pneumonia: general onset of rapid onset, systemic toxicity symptoms, cough, cough and blood stasis, most patients are thin. The condition is heavier and prone to complications. The white blood cell count and the neutrophil ratio were significantly increased.
2, Streptococcus pneumoniae infection: clinical features are local redness, swelling, heat, pain and dysfunction. Fever is accompanied by varying degrees of symptoms of toxemia, such as headache, nausea, vomiting, bloating, abdominal pain, general discomfort, muscle and joint pain. It is generally necessary to identify the culture by sputum culture.
