Moraxella catarrhalis infection
Introduction
Introduction to Moraxella catarrhalis infection Neisseria includes five genera: Neisseria, Moraxella, Trichoderma, Acinetobacter, and Oligella, among which Moraxella includes Moraxella and Branhamella. Two subgenus, there is still controversy about the above naming and classification. Moraxella catarrhalis (MC) also known as Branhamella catarrhalis (BC) is a bacterium of the genus Moraxella that resides in the upper respiratory tract of humans. It was classified as Branhamella in 1970, 1984. The bacterium is classified as a subgenus of Moraxella, known as Moraxedla (Branhamella) catarrhalis, or catarrhal, and is currently widely accepted as M. catarrhalis (MC) or catarrh. Pulling bacteria. With the in-depth study of the bacteria of this genus, its naming will also change. MC bacteria is a Gram-negative diococcus. In the past, it was considered to be only a normal colony of the respiratory tract of healthy people. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of infection: non-infectious Complications: respiratory failure
Cause
Ethamella infection cause
(1) Causes of the disease
MC grows well on various media such as blood plate and chocolate plate. The colony is in the form of "ice ball". The colony is smooth, the diameter is 1-3 mm, opaque, milky white, easy to scrape off from the medium, the bacteria are no spores, no flagella. It is easily confused with other Neisseria species. MC can produce oxidase, enzyme and DNase. The GC content in the genomic DNA of the bacteria is 40.0~40.3mol%. The understanding of the surface structure of MC is helpful to elucidate the cause of bacteria. The disease mechanism, the human body's immune response to bacteria, the development of vaccines, etc., the MC isolated from different regions is purified by the outer membrane protein (OMP), sodium dodecyl sulfate polyacrylamide gel. Electrophoresis (SDS-PAGE) analysis revealed that the components were highly similar. The characteristics of the main OMP have been elucidated and used in the development of vaccines. The MC outer membrane contains lipid-oligosaccharides (LOS), which consist of a lipid A core and oligomerization. Sugar coupling, 95% of the isolates contain three major antigens, LOS, which are classified into different serotypes depending on the sugars attached to the ends of the LOS molecule. LOS may also be a virulence component of MC pathogenesis, and most MCs express Umbrella It binds to the sugar (neural) sphingolipid receptor of human epithelial cells, thereby adhering to the epithelial cells of the respiratory tract, and initiates the process of infection.
(two) pathogenesis
MC can cause mucosal infections in children and adults. The colonization of bacteria from the respiratory tract can spread the clinical symptoms of infection to the adjacent areas. The MC of the nasopharynx can enter the middle ear through the Eustachian tube to cause otitis media. Studies have confirmed the cause of otitis media. The colonization of MC in the respiratory tract is the first step in the development of otitis media. However, the colonization of pathogens does not necessarily cause infection. The mechanism of how the MC of adult COPD patients migrate from normal sites causes lower respiratory tract infections. OMP has A. 8 major proteins such as H, with a molecular weight of (21-98)×103, have hemagglutination. In recent years, a new 0MP is called high molecular weight OMP or ubiquitous surface protein A (UspA). It has attracted widespread attention and is encoded by two genes. The homology of the encoded protein sequence is more than 90%. The mutation of the UspAl-encoding gene results in greatly reduced adhesion of the encoded protein. The purified protein has HEp-2 cells. It is ecotropic and binds to fibronectin, and the virulence of this phenotype is reduced; the UspA2 gene is a complement resistance gene. The protein is easy to bind to the vitreous s protein. Animal experiments have shown that these two proteins have the function of scavenging bacteria from the lungs. The two proteins of UspA are the most studied MC proteins, and their development as a vaccine has not been successful. There are two receptors on the surface called transferrin binding protein (TbpA and TbpB), lactoferrin-binding proteins (LbpA and LbpB), and the genes encoding these proteins share partial homology, and these proteins are also present in Nesser. The surface of Gram-negative bacteria such as bacteria and Haemophilus is a causative agent of bacteria. The change or deletion of the coding gene can affect its pathogenicity and immunogenicity. The -lactamase produced by MC not only protects the bacteria. Various pathogenic enzymes, and other serious respiratory tract infections such as Streptococcus pneumoniae, untyped Haemophilus influenzae infection is ineffective for penicillin treatment, bacterial resistance-related gene transmission can occur, such as Bootsma It was found that MC and Gram-positive microorganisms occasionally have cross-resistance genes, which indicates that MC has indirect pathogenicity. In fact, treatment failure due to the above situation has been reported. It indicates that whether MC is pure culture positive or mixed culture positive has important clinical significance. In elderly patients, sputum specimens can often isolate complement-tolerant strains. Complement tolerance can be considered as a pathogenic factor of MC: 89% of children Lower respiratory tract isolation MC strains are tolerant to complement-mediated killing; while upper respiratory tract isolates are mostly sensitive (58%), complement-tolerant strains can bind to human vitreous binding proteins to form membrane complexes that impede complement attack. , thereby inhibiting the final pathway of complement.
Prevention
Moraxella infection prevention
Children and adults develop specific IgG after infection, which may have protective effects. Animal models of MC infection indicate that mucosal immunization with mice is better than systemic immunity. B1, CopB/OMP B2, LbpB, OMP in OMP CD, OMP E, OMP G, TbpB and UspA have all been used in vaccine research, but there is no definitive conclusion. It is estimated that it will take 10 years to develop an effective vaccine for clinical use.
Complication
Complications of Moraxella catarrhalis infection Complications, respiratory failure
Concurrent respiratory failure and circulatory failure.
Symptom
Symptoms of Moraxella catarrhalis common symptoms dyspnea bacterial infection abscessation diabetes
The bacteria can cause a variety of human infections, such as acute otitis media, maxillary sinusitis and lower respiratory tract infections, can also cause meningitis, endocarditis, urethritis, infant and child conjunctivitis, keratitis and sepsis, recently reported MC Can cause male and female sexual genitourinary infections such as vestibular gland abscess, male urethritis, etc., the strain produces -lactamase strains, which brings certain difficulties for clinical treatment, otitis media: 80% of children before 3 years old Have had at least one otitis media, children with recurrent otitis media often accompanied by delayed language development, tympanostomy for otitis media, multi-center study, 20 years in the United States and Europe, 15 centers to puncture the middle ear fluid The identification of cultures has reached a completely consistent conclusion: the main pathogens of otitis media are Streptococcus pneumoniae, Haemophilus influenzae and MC, of which 15% to 20% are MC. Recently, more sensitive PCR methods than bacterial culture have been adopted. Identification of the puncture fluid may result in a higher positive rate of MC, lower respiratory tract infection in patients with COPD: because of the staining and colonization of MC and other Neisseria from Gram It is difficult to distinguish between the two, so until the last 15 years, the lower respiratory tract infection caused by COPD has been paid attention to. The following evidence indicates that MC infection accelerates the progression of COPD: COPD patients with accelerated progression of sputum Gram-stained dominant bacteria are MC, Sometimes even for MC pure culture; some patients with accelerated COPD condition can be cultured purely by tracheal aspiration; MC is considered to be a condition in which MC infection causes worsening of COPD, and the condition is improved after applying effective antibacterial drugs; The worsening person can detect a specific immune response to MC.
It is currently estimated that MC infection is the second cause of worsening COPD after uninfected Haemophilus influenzae infection. 30% is caused by MC. The clinical manifestations of COPD patients after MC infection are no different from those of other bacterial infections. Cough, increased cough, increased difficulty in breathing, etc., a large number of Gram-negative diplococcus can be found inside and outside the Gram-stained cells of the sputum specimens. Pneumonia in the elderly: The research centers in the United States and Europe found that MC is causing a considerable proportion of elderly pneumonia patients. The pathogen, because MC can parasitize the respiratory tract without any symptoms, it is difficult to accurately determine the proportion of pneumonia in the elderly, but a prospective study showed that 10% of community acquired pneumonia in the elderly is caused by MC, most infected people have Basic diseases such as COPD, heart failure, diabetes, etc. Although the elderly are critically ill after MC pneumonia, fulminant pneumonia is rare, and nosocomial respiratory infections: In the 1980s, people were concerned that MC can cause lower respiratory tract infections in hospitals. Reports of outbreaks in respiratory wards, these adult patients often have a basis for pulmonary heart disease, an isolated strain for outbreaks The identification found that some outbreaks were caused by multiple MC strains, while other outbreaks were from the same clone, indicating that MC can be transmitted from person to person. Sinusitis: specimens of patients with sinusitis can be obtained by sinus lavage. The pathogens causing sinusitis in adults and children are followed by untyped Haemophilus influenzae, Streptococcus pneumoniae and MC, sepsis: Recently, there have been reports in the literature that MC can cause sepsis, and the septicemia caused by MC is rare and can occur in people of any age. In the case of neonatal to elderly, the disease manifests a large difference, ranging from mild symptoms to life-threatening. The underlying disease is a key factor in determining the prognosis. After viral infection, MC can cause bacterial bronchitis in children, and MC can also cause eye in children. There is also a case of fatal meningitis caused by conjunctivitis and keratitis.
Examine
Examination of Moraxella catarrhalis infection
Bacteriological tests should be obtained as early as possible according to different infection sites and bacteriological identification. The traditional method is based on the degradation reaction of sugars and nitrate reduction test. This method requires a large number of bacteria, which takes a long time and is prone to false positives. Continuously introduce fast, accurate and simple methods, such as improved sugar degradation test; rapid enzyme test of chromogenic substrate; hydrolysis test of butyrate oil; butyrate test, wherein: Bacto-TB hydrolysis test is specific and practical. Simple, low cost, etc., can quickly identify MC, based on LPS-based serological typing, -lactamase protein isoelectric focusing, protein outer membrane electrophoresis spectrum has been used for MC phenotypic identification, recently based on nucleic acid polymorphism Sexual restriction enzyme analysis, macrorestriction enzyme and pulsed-field gel electrophoresis (PFGE) technology also provide a powerful weapon for bacteriological detection. Strain-specific DNA probes have also been tested in clinical, fragment length polymorphisms. Analysis (FLPA) and automated karyotyping systems for the identification of clinical isolates found that resistant MC is a heterogeneous gene of the same species, derived from the formation of a clone. Reproduction, in addition, PCR and 16S rRNA gene sequencing can be used to accurately identify MC, and multiplex PCR technology for the determination of three or more common pathogens has also been clinically applied. Blood routine examination of white blood cell count and neutral granules The number of cells is significantly increased, and there may be a left shift of the nucleus, but the lower body response such as low immunity or white blood cells such as the elderly and children may not be high, and imaging examination may be used for auxiliary diagnosis of infections such as lungs and sinuses.
In the case of pulmonary infection, X-ray chest radiographs showed abnormal lesions.
Diagnosis
Diagnosis and identification of Moraxella catarrhalis infection
According to the clinical manifestations of each system, laboratory tests, etc. can determine the location of infection, bacterial culture to MC is the basis for diagnosis, it should be noted that the clinical manifestations of infection in patients with underlying diseases and low immunity can be atypical, relying on sputum culture biochemistry Identification and smear Gram staining, if necessary, molecular biological testing.
Attention should be paid to the identification of other Neisserial bacteria.
