What is Hemophilic Infection?
Hemophilic infection – acute infectious diseases caused by the stick of influenza, is characterized by a primary lesion of the respiratory system, the central nervous system and the development of purulent foci in various organs. Children get sick more often.
Causes of Hemophilic Infection
The causative agent, Haemophilus influenzae (bacillus influenzae, Pfeiffer bacillus), belongs to the genus of hemophilus (which includes 16 species of bacteria) and is of the greatest importance in human pathology. It is a small coccobacillus (0.3-1 μm in diameter), for its growth requires the presence of thermolabile factor Y and thermostable factor X contained in erythrocytes. According to cultural properties (production of indole, urease activity, etc.), it is divided into 7 biotypes ( from 1 to VII). A part of the secreted mucous membranes of Influenza sticks has capsules. There are 6 known antigenically distinct capsular types, denoted from A to F. Haemophilus influenzae type b has the greatest significance in human pathology. Influenza bacillus is sensitive to ampicillin, chloramphenicol, tetracycline antibiotics, but in recent years there has been an increase in pathogen resistance to ampicillin and other antibiotics.
The source and reservoir of infection is only man. The pathogen is localized on the mucous membrane of the upper respiratory tract. It can be distinguished from the nasopharynx in 90% of healthy people, and about 5% of all isolated strains fall into the more virulent type b. A healthy carrier state can last from several days to several months. Carrier is maintained even with a high titer of specific antibodies and even with the appointment of high doses of antibiotics. Children most often get sick at the age of 6-48 months, less often – newborns, older children and adults. The incidence rates of hemophilic type b infection are thousands of times higher in children of susceptible ages and in individuals with certain types of pathology (sickle cell anemia, agammaglobulinemia, persons with spleen removed, patients with lymphogranulomatosis who receive chemotherapy). The greatest danger to these individuals is contact with patients with hemophilic infection. The incidence increases in late winter and spring. In recent years, the incidence of adults has increased markedly. The infection is transmitted by airborne droplets.
The incidence increases in late winter and spring. In recent years, the incidence of adults has increased markedly.
It should be noted that the variant of the clinical form of hemophilus infection depends on age. Thus, according to foreign data, meningitis is more common in children aged 6–9 months, epiglottitis is more common in children older than 2 years, cellulite (inflammation of the subcutaneous tissue) is more common in children at the age of one year. For adults and the elderly, meningitis is uncharacteristic – pneumonia is more common.
Pathogenesis During Hemophilic Infection
The gated infection is the nasopharyngeal mucosa. The transmission mechanism is airborne, but in young children the transmission path may be contact. The pathogen can persist for a long time in the gate area of the infection in the form of a latent asymptomatic infection. In some cases, mainly in persons with weakened defensive forces and persons at risk, the latent form becomes manifest. The risk of transition of inapparent carriage into manifest form increases with the presence of concomitant viral infection and an increase in the microbial mass. It is necessary to note the role of secondary contacts. This transmission mechanism is most relevant for children under two years of age. It is necessary to distinguish the primary disease, which occurs due to contact with a healthy carrier and secondary, which occurs when contact with the patient in manifest form. The infection spreads to the surrounding tissues, causing the development of sinusitis, otitis, bronchitis, pneumonia, inflammation of the subcutaneous fatty tissue, or by hematogenous dissemination affects joints and other organs, leaking according to sepsis. Strains of a hemophilus bacillus without capsules affect only mucous membranes. Systemic diseases are caused only by pathogens possessing a capsule, in 95% of cases this is a hemophilus bacillus type b. A unique property of bacteria of this type is their ability to enter the bloodstream by severing the intercellular connections. Also, a more pronounced pathogenicity of these strains is due to the fact that the capsule is able to suppress phagocytosis. The pathogen may persist in the bloodstream asymptomatically for several days until the mass of microbial bodies becomes critical. Then the bacterium enters the CNS through choroidal plexus, causing infiltration and purulent inflammation of the pia mater. Have suffered a disease develops durable immunity.
The body’s immune response to this type of infection has several features. Due to the suppression of phagocytosis, the production of antibodies by B-lymphocytes is activated without the participation of T-helpers. That is why the immune response of the body in response to Hib invasion in most cases is insufficient, there is no so-called. booster (shock) response during re-exposure of the antigen of a hemophilic rod. There is also an extremely weak T-independent production of specific antibodies under the age of 18 months. In addition, polysaccharides are a set of oligosaccharides, each of which is able to induce a weak immune response. This in turn determines the multiplicity and variability of antibodies produced to the detriment of the quantitative factor. The local immunity represented by IgA class secretory antibodies is not well understood. Moreover, it was found that the capsular species of H.influenzae secrete proteases that inactivate antibodies. Studies of local immunity in healthy carriers have shown that the role of local immunity can be quite important – blocking the penetration of mucous membranes by bacteria, preventing the penetration of microorganisms into the bloodstream. A complement for a hemophilic infection can be activated both by the classical (antibody-dependent) pathway and by an alternative pathway. H.influenzae cell wall antigens are able to activate complement along an alternative pathway, while a complex of antibodies and antigens is capable of activating complement along the classic pathway.
Symptoms of Hemophilic Infection
The duration of the incubation period is difficult to establish, since the disease is often a consequence of the transition of latent to manifest infection. A local inflammatory process of the respiratory mucosa may develop or hematogenous diseases develop.
Hemophilic bacillus type b is one of the common causes of generalized infection (bacteremia) in children, half of them develop purulent meningitis, quite often (15-20%) pneumonia and less often other focal lesions. As a rule, hemophilic infection is acute, but some clinical forms can take a protracted course.
Hemophilic infection can occur in the following clinical forms:
- purulent meningitis;
- acute pneumonia;
- inflammation of the subcutaneous tissue;
- purulent arthritis;
- other diseases (pericarditis, sinusitis, otitis media, respiratory diseases, etc.).
Purulent meningitis occurs mainly in children from 9 months to 4 years (for this age group this is the most common cause of meningitis). The disease begins acutely, sometimes with symptoms of acute respiratory infections, then rapidly develops clinical symptoms characteristic of bacterial meningitis. Sometimes meningeal syndrome is combined with other manifestations of a hemophilic infection (purulent arthritis, inflammation of the epiglottis, cellulitis). The disease is severe and often lethal (about 10%).
Hemophilic pneumonia can manifest itself both as focal and lobar (lobar), very often (up to 70%) accompanied by purulent pleurisy (in children), may be complicated by purulent pericarditis, inflammation of the middle ear. May take a protracted course. In adults, especially in elderly people, a hemophilic infection can build up on other lung diseases.
Hemophilic sepsis often develops in children 6–12 months of age who are predisposed to this disease. It flows violently, often as lightning, with septic shock and rapid death of the patient. Secondary lesions in this form is not observed.
Inflammation of the subcutaneous tissue (cellulite) also develops in children up to 12 months, more often localized on the face. Often begins with a picture of acute respiratory infections (rhinopharyngitis), then swelling appears in the cheek area or around the orbit, the skin over the swelling is hyperemic with a cyanotic shade, sometimes the disease is accompanied by inflammation of the middle ear. Body temperature is low-grade, symptoms of general intoxication are mild. In older children, the inflammation of the subcutaneous tissue may be localized on the extremities.
Inflammation of the epiglottis (epiglottitis) is a very severe form of hemophilic infection, in most cases (about 90%) is accompanied by bacteremia. It begins acutely, characterized by a rapid rise in body temperature, severe general intoxication and a picture of rapidly progressing croup, which can lead to the death of a child from asphyxia (complete obstruction of the respiratory tract or respiratory arrest).
Purulent arthritis is a consequence of hematogenous drift of a hemophilic rod, often accompanied by osteomyelitis. Other manifestations of hemophilic infection are rare.
Diagnosis of Hemophilic Infection
In recognition, it is necessary to take into account the age of the patient, the presence of factors contributing to infection with a hemophilic rod, characteristic clinical manifestations (cellulitis, epiglottitis, etc.). Confirmation of the diagnosis is the release of hemophilic sticks (pus, sputum, cerebrospinal fluid, material taken from the mucous membranes). In the cerebrospinal fluid (and sometimes in the urine), the capsular antigen of a hemophilus bacillus can be detected using the reaction of a counter immunoelectrophoresis or an immunoassay method.
Treatment for Hemophilic Infection
Without etiotropic therapy, some forms of hemophilic infection (meningitis, epiglottitis) almost always result in the death of the patient. It is necessary to start etiotropic therapy as soon as possible. Ampicillin was considered the most effective and low-toxic until 1970, when the fact of antibiotic resistance was found in H. influenzae, was considered ampicillin, but in recent years hemophilus bacillus strains that are resistant to this antibiotic have become more frequent. H.influenzae is resistant to penicillins, some of the strains produce penicillinase. Ampicillin is administered intravenously at a daily dose of 200-400 mg / kg / day for children and 6 g / day for adults. In some recommendations, in particular in the leadership of the American Pediatric Academy, it is proposed to apply ampicillin, cephalosporins in combination with chloramphenicol from the very beginning. However, according to recent studies, strains of hemophilus bacilli circulating in these areas are resistant to almost all classes of antimicrobial drugs. Recently, there has been information in domestic and foreign publications about a higher, than for ampicillin, effectiveness of antibiotics such as amoxiclav (co-amxiclav, biseptol) and azithromycin (sumamed), even when used in short courses.
Prevention of Hemophilic Infection
Healthy carriers of hemophilus bacillus type b and those at risk who come in contact with patients with hemophilic infection are advised to take rifampicin orally at a dose of 10–20 mg / kg / day (maximum 600 mg / day) once a week after registering the first case of the disease. for 4 days.
In 1974, the first large-scale study of the efficacy of a capsular polysaccharide vaccine was carried out in Finland, which was included in the annals of the history of Hib vaccination. It was found that the vaccine is extremely effective (55-85% with a confidence level of 95%) at the age of 18-71 months and provides 4-year protection in 90% of cases. However, more modest results were obtained in children under the age of 18 months.
Later, numerous tests of polysaccharide vaccines were conducted in Europe and North America. In particular, a clinical trial in the UK (1991-1993) showed a 87% reduction in the incidence of hemophilic meningitis. In Holland, when conducting a similar study, there was a complete absence of cases of hemophilic etiology meningitis within 2 years after the start of immunization.
Currently, compulsory immunization against hemophilic infection has been introduced in the United States (1990), Canada (1990), and several other countries.