Overview of Haemophilus influenzae
Haemophilus influenzae, short for Haemophilus influenzae, is a normal bacterial group that resides in the upper respiratory tract of humans and belongs to the genus Haemophilus, which is named Haemophilus because it must be cultured artificially with fresh blood or blood components to grow. Haemophilus influenzae is the most common bacterium in the genus Haemophilus that is pathogenic to humans and can cause primary septic infections and secondary infections of the respiratory tract.
Etiology
Pathogenic bacteria can be divided into six biotypes according to different biochemical reactions: I, II, III, IV, V and VI. Pathogenicity is mostly of type I, II, III and IV. According to the different antigenicity of podocarp polysaccharide, podocarp bacteria can be divided into 6 serotypes: a, b, c, d, e and f. Among them, type b has the strongest pathogenicity, followed by e and f. According to the bacterial outer membrane proteins (OMP), they can be divided into different subtypes. Those with pods are more pathogenic than those without.
Haemophilus influenzae is mainly transmitted from person to person through the respiratory tract, and can also cause suppurative infections of the skin and soft tissues through direct contact, as well as infection of the fetus through the birth canal of pregnant women. Neonates have low morbidity within 2 months of birth due to passive immunization from the mother, while infants and young children from 2 months to 3 years of age have the lowest level of serum antibodies and are susceptible to infection during this period.
Symptoms
1. Pneumonia
Adult patients are mostly patients with existing chronic respiratory diseases, manifesting as bronchopneumonia, segmental pneumonia, multilobar pneumonia and lobar pneumonia. Half of the pleura is involved, but the occurrence of pyothorax is rare. Most are caused by b organisms with pods, but some patients are caused by pod-less organisms. The prognosis depends on the original health status of the patient, and the morbidity and mortality rate can be more than 30%.
2. Genitourinary tract infection
The bacteria can cause prostatitis and urethritis in men, endometritis, salpingitis and abscess in women, cervicitis, vaginitis, urethritis, puerperal fever and neonatal bacteremia. Bacteria mostly cannot be divided into serotypes, and the biotypes are Ⅰ, Ⅱ, Ⅲ, Ⅳ. Ⅰ, Ⅱ, Ⅲ mostly seen in respiratory tract infections, Ⅳ type is more unique in genitourinary tract infections, so some people will not be able to distinguish serotypes of biological Ⅳ type bacteria called genitourinary tract type.
3. Meningitis
More than 60% of infantile purulent meningitis is caused by this organism, and from the 1950s to the 1980s, the incidence in children under 5 years of age increased sixfold. The incidence in adults used to be low, at 1% to 3%, but in recent years the incidence has also increased, and has been reported to be as high as 20%. Adults tend to have primary lesions, such as sinusitis, pneumonia, epiglottitis, etc., especially prone to head trauma or cerebrospinal fluid leakage, the causative organisms are mostly b-type bacteria. Clinical manifestations and cerebrospinal fluid examination are similar to other purulent meningitis. Adult mortality rate is 10%～20%.
4. Epiglottitis
Most patients are healthy and young. The manifestations are fever, sore throat, due to the rapid swelling of the pharynx can lead to respiratory tract obstruction, which is the main cause of death in this disease. Therefore, patients with rapid development of pharyngeal swelling should be intubated promptly.
5. Other purulent infections
(1) Appendicitis, it has been reported that 376 cases of surgical excision of appendix specimens were subjected to bacterial culture, and the culture results showed that this bacterium accounted for 4%;
(2) Biliary tract infection, can cause chronic cholecystitis and cholelithiasis;
(3) Cellulitis, mostly in children;
(4) Septic arthritis, which can involve a single joint or multiple joints;
(5) Sinusitis;
(6) Osteomyelitis;
(7) Epididymitis;
(8) mastoiditis, etc.
6. Secondary infection
It often occurs after respiratory infections such as influenza, measles, whooping cough, tuberculosis, etc. It is also often the etiologic agent of secondary infections of chronic bronchitis, and it can also cause sinusitis and otitis media secondary to viral infections in children.
Laboratory examination
1. Pathologic examination
(1) Smear direct examination Sputum of pneumonia patients, cerebrospinal fluid of meningitis patients, purulent secretions from the foci of suppurative infections can be examined by smear staining, and gram-negative bacilli can be found to help diagnosis.
(2) Bacterial culture Culturing of pathogenic bacteria in blood, cerebrospinal fluid, urine and local secretions can be used as the basis for diagnosis; immunochemical identification of podoconiosis reaction of newly isolated bacteria and examination of podoconiosis material from the above specimens of body fluids and concentrated urine can also be used as the supporting evidence. Positive pharyngeal and sputum cultures may only be a carrier state, and whether it is a clinical infection should be considered in conjunction with clinical manifestations and other examinations.
(3) Convection immunoelectrophoresis (CIE) Bacterial culture and CIE for Hib antigen in the cerebrospinal fluid of children with bacterial meningitis found that the positive rate of bacterial culture was 13.3% (8/60), and the positive rate of CIE was 90% (54/60); among them, the positive rate of culture for Haemophilus influenzae type b was 5.0% (3/60), and the positive rate of CIE for Haemophilus influenzae type b was 51.7% (31/60).
(4) Bacterial nucleic acid examination Polymerase chain reaction (PCR) has been tried to examine bacterial specific nucleic acid fragments, but the sensitivity and specificity are not stable enough and are still under study.
(5) Immunological tests Enzyme-linked immunosorbent assay (ELISA) to detect specific IgM antibodies and reverse hemagglutination assay to detect bacterial antigens are faster than bacterial culture.
(6) Other tests Depending on the location of the infection, X-rays, CT and other tests may be chosen to assist in the diagnosis. The X-ray presentation of patients with pneumonia is similar to that of pneumococcal pneumonia.
2. Blood picture
The white blood cell count can be in the normal range in mild cases, but in severe cases, it can be increased to more than 10×109/L, and the neutrality can be more than 80%.
3. Cerebrospinal fluid examination
Similar to other cases caused by septicemia, protein is increased, sugar and chloride are decreased, leukocyte count is increased to more than 1000×106/L, and multinucleated cells account for the majority.
Diagnosis
1. Pathologic examination
(1) Smear direct examination Sputum of pneumonia patients, cerebrospinal fluid of meningitis patients, purulent secretions at the foci of septic infections, can do smear staining examination, such as the discovery of gram-negative short bacilli can help diagnosis.
(2) Bacterial culture Culturing of pathogenic bacteria in blood, cerebrospinal fluid, urine and local secretions can be used as the basis for diagnosis; immunochemical identification of podoconiosis reaction of newly isolated bacteria and examination of podoconiosis material from the above specimens of body fluids and concentrated urine can also be used as the supporting evidence. Positive pharyngeal and sputum cultures may only be a carrier state, and whether it is a clinical infection should be considered in conjunction with clinical manifestations and other examinations.
(3) Convection immunoelectrophoresis (CIE) Bacterial culture and CIE for Hib antigen in the cerebrospinal fluid of children with bacterial meningitis found that the positive rate of bacterial culture was 13.3% (8/60), and the positive rate of CIE was 90% (54/60); among them, the positive rate of culture for Haemophilus influenzae type b was 5.0% (3/60), and the positive rate of CIE for Haemophilus influenzae type b was 51.7% (31/60).
(4) Bacterial nucleic acid examination Polymerase chain reaction (PCR) has been tried to examine bacterial specific nucleic acid fragments, but the sensitivity and specificity are not stable enough and are still under study.
(5) Immunological tests Enzyme-linked immunosorbent assay (ELISA) to detect specific IgM antibodies and reverse hemagglutination assay to detect bacterial antigens are faster than bacterial culture.
(6) Other tests Depending on the location of the infection, X-rays, CT and other tests may be chosen to assist in the diagnosis. The X-ray presentation of patients with pneumonia is similar to that of pneumococcal pneumonia.
2. Blood picture
The white blood cell count can be in the normal range in mild cases, but in severe cases, it can be increased to more than 10×109/L, and the neutrality can be more than 80%.
3. Cerebrospinal fluid examination
Similar to other cases caused by septicemia, protein is increased, sugar and chloride are decreased, white blood cell count is increased to more than 1000×106/L, and multinucleated cells account for most of the cases.
Treatment
1. General and symptomatic treatment
According to the different diseases of the patients, appropriate symptomatic treatment should be given. For example, expectoration and cough suppression for patients with pneumonia, dehydration and lowering of cranial pressure and prevention of cerebral edema for patients with meningitis.
2.Pathogenic treatment
In the past, ampicillin and penicillin were mainly applied, but in recent years, due to the obvious increase of drug-resistant strains, fluoroquinolones, third-generation cephalosporins, erythromycin (including erythromycin and azithromycin) with higher sensitivity have been used instead. The dosage and duration of treatment depend on the severity of the disease, with oral administration in mild cases and intravenous administration in severe cases. For patients with meningitis, drugs that can cross the blood-brain barrier and reach effective therapeutic concentrations in the cerebrospinal fluid, such as cefotaxime and ceftriaxone, should be used. Since the drug resistance of bacteria is constantly changing, the drugs should be selected according to the local drug sensitivity, and be adjusted after the results of bacterial drug sensitivity of the patient are available.