OVERVIEW
Haemophilus influenzae meningitis was isolated by Pfeiter in 1892 from the nasopharyngeal secretions of an influenza patient. The vast majority of H. influenzae meningitis is caused by H. influenzae type b. The majority of meningitis is caused by H. influenzae type b. H. influenzae is generally found in the upper respiratory tract of humans and is classified into six serotypes, a, b, c, d, e, and f, based on the antigenic composition of the pod polysaccharide, using type-specific immune sera for the pod swelling test. Of these, type b is the most pathogenic in humans (infants and young children). H. influenzae only invades human beings, the age of onset is mainly 3 months to 3 years old infants, because infants less than 2 months old have antibodies from the mother to kill bacteria, so they seldom get sick, and then with the growth of age, the specific antibodies from the mother to kill bacteria declined, and their own have not been able to produce a sufficient amount of antibodies, so they are susceptible to this disease. 5 years old and above and the adults seldom develop the disease. Children over 5 years of age and adults rarely develop the disease. If the disease develops after 5 years of age, it is important to check for anatomical and immunodeficiency defects. The disease can develop throughout the year, but it is most common in the fall and winter seasons.
Causes
Most cases of H. influenzae meningitis are caused by H. influenzae type b. H. influenzae is generally found in humans. Influenza bacilli are generally found in the upper respiratory tract of humans and are classified into six serotypes, a, b, c, d, e, and f, according to the antigenic composition of the polysaccharide in the pods, using type-specific immune sera for the pod swelling test. Among them, type b is the most pathogenic to humans (infants and children). H. influenzae only invades human beings, and the age of onset of the disease is mainly between 3 months and 3 years old, because infants less than 2 months old have bactericidal antibodies in their bodies from their mothers, so they rarely get the disease, and then with the growth of age, the specific bactericidal antibodies from the mothers decline, and they are not yet able to produce sufficient antibodies, so they are susceptible to the disease.
Symptoms
The disease starts slowly with obvious symptoms of upper respiratory tract infection, pneumonia or otitis media. After a few days to one or two weeks, symptoms of meningitis appear. Most of the children have fever and vomiting, lethargy, coma, convulsions, cervical ankylosis and bulging fontanel, etc. Occasionally, there are ecchymoses on the skin and mucous membranes. Complications include subdural effusion, hydrocephalus, brain abscess, etc. Mainly subdural effusion (all kinds of purulent meningitis can occur, but influenza meningitis is more common), which often occurs in infants under 1 year old, and subdural effusion can be asymptomatic, but there are cases in which the fever goes down and then rises again, or the temperature does not go down even after several days of treatment; or after the symptoms get better, there are again convulsions, vomiting, fontanelle bulging, and the head circumference is enlarged. Cranial X-ray and subdural puncture should be performed to assist in the diagnosis. Severe cases may have sequelae, such as ataxia, paralysis, blindness, deafness and mental retardation.
Examination
1. Laboratory examination
Routine cerebrospinal fluid is similar to other bacterial meningitis. Gram-negative bacilli are often found in the smear, and the positive rate is higher than that of rheumatoid encephalitis, and the positive rate of blood culture is also high. The positive rate of blood culture is also high. The pod swelling test can identify the type of influenza bacillus, and the positive result of horseshoe crab cytolysate test to measure endotoxin in the cerebrospinal fluid is helpful for the diagnosis of this disease. In recent years, the use of convection electrophoresis, latex agglutination test, ELISA and other immunological methods to detect the cerebrospinal fluid in the podocarp polysaccharide antigen can quickly make a pathogenic diagnosis, and the positive rate can reach 80%.
2. Other auxiliary examinations
Cranial X-ray examination can detect abnormalities.
Diagnosis
Positive cerebrospinal fluid smear and culture are the main basis for diagnosis.
Differential diagnosis
The disease should be distinguished from pneumococcal meningitis.
Complications
There are subdural effusion, hydrocephalus, brain abscess and so on.
Treatment
Ampicillin is a broad-spectrum antibiotic with bactericidal effect, in the case of meningitis, the cerebrospinal fluid concentration of the drug is 30% of the blood concentration, which is effective in the treatment of this disease. Ampicillin is preferred for non-enzyme-producing strains of influenza bacillus, which cause meningitis. Intravenous push (15-20 minutes per push or intravenous drip) can also be injected intramuscularly, the course of treatment is not less than 10 days or after the use of the drug until 7 days after the fever subsides. In recent years, there have been reports of resistance of this bacterium to ampicillin, and the time for fever to subside is longer and the relapse rate is higher after the use of the drug. Chloramphenicol is more toxic to newborns, so its dose should be reduced to 25mg/(kg-d). In recent years, due to the widespread prevalence of β-lactamase-producing strains, foreign countries advocate the use of cefotaxime or ceftriaxone. Ceftriaxone in the cerebrospinal fluid bactericidal efficacy is strong, the concentration of the drug in the cerebrospinal fluid greatly exceeds the minimum inhibitory concentration (MIC) of the bacterium, so the removal of bacteria in the cerebrospinal fluid is faster, fewer after-effects such as deafness after the use of the drug, the recovery of abnormal neurological signs faster, fewer side effects.