Staphylococcus epidermidis pneumonia
Introduction
Introduction to Staphylococcus epidermidis pneumonia Staphylococcus epidermidis (SE) can cause pneumonia. Can be divided into primary (inhalation) and secondary (blood) sex. The onset is rapid, the symptoms of systemic toxicity are obvious, coughing, cough and blood stasis, and most patients are thin. The condition is heavier and prone to complications. The white blood cell count and the neutrophil ratio were significantly increased. Treatment with active antibiotics and supportive therapy, accompanied by empyema or other sites of purulent disease, should be promptly cut open drainage. basic knowledge Proportion of the disease: the incidence rate is 0.0230% in the susceptible population Susceptible people: no specific people Mode of infection: non-infectious Complications: bacteremia, osteomyelitis, septic arthritis
Cause
Staphylococcus epidermidis pneumonia
Causes:
There are 31 species of staphylococci, half of which can live in the human body. Staphylococcus aureus and SE are the most commonly colonized species in the human body and the most susceptible to disease. According to the sensitivity of bacteria to methicillin, staphylococcus is divided into Sensitive and resistant parts are divided into negative and positive according to the condition of coagulase. SE is the common coagulase-negative staphylococci (CNS). Kleeman reported that 499 strains of CNS, SE accounted for 64.5%, Staphylococcus haemolyticus 13.4%, human grapes Cocci is 7.4%. CNS is often the pathogen of foreign body infections (such as artificial catheters). Mack believes that hexose is the main component of glycogen and plays a role in SE. Christensen reported that a mucus-associated antigen (SAA) also has this type of Role, Baldassarri L on the bacterial surface of 50 strains of SE on the mucus layer and / or SAA detection, the results of 37 strains (74%) with strong or weak mucus layer, 22 of these 37 strains (59.4%) SAA positive, but No mucus layer negative and SAA positive, which also indicates that there is more than one antigen in the mucus layer. The CNS mucus (ESS) has a certain relationship with pathogenicity.
1 The bacteria covered by mucus are protected.
2ESS interferes with the phagocytosis of normal conditioning.
3 inhibits lymphocyte transformation induced by hemagglutination of plants.
4 The penetration of bacteria in the effective antibiotics is directly inhibited by certain antibiotics. In addition, the adhesion of SE to artificial catheters is mediated by its capsular polysaccharide/adhesion factor (PS/A), and PS/A is still very Strong immunogenicity, Shang's et al. believe that foreign body infection and SE caused endocarditis, the pathogenesis of osteomyelitis is a typical surface infection.
Pathogenesis:
The first step in the pathogenesis of SE is adhesion. This bacterium usually adheres to the surface of the skin and mucous membrane. The mediating effect of adhesion is non-specific in the absence of protein. If foreign matter enters human tissue or blood vessels, it will It is rapidly surrounded by matrix proteins. Two substances are very important in adhesion. One is the linear homologous glycine N-acetylaminopolyglucose called intercellular adhesin; the other is NOKD2 protein, which removes polysaccharides. Or the gene of the protein will significantly change the function of the isogenic strain. The mutant strain still has the surface adhesion ability, but loses the accumulation function, and then the specific mechanism mediates the adhesion of the bacteria, which occurs between the epitope of the matrix protein and the SE structure. The interaction between the receptor and the ligand, the second step is accumulation: the bacteria proliferate on the surface and develop on the surface of other bacteria, because an intercellular adhesion mechanism allows SE to accumulate and grow into a cell population.
Prevention
Staphylococcus epidermidis prevention
Actively treat skin edema, suppurative osteomyelitis and deep abscess infections, take strict disinfection and standard operation in the hospital to prevent cross-infection, chronic patients should strengthen nutrition support and increase immunity, try to avoid abuse of antibiotics and immunosuppressants Etc., are all necessary measures to prevent this disease.
Complication
Staphylococcus epidermidis pneumonia Complications bacteremia osteomyelitis septic arthritis
Can cause bacteremia with endocarditis, osteomyelitis, septic arthritis.
Symptom
Symptoms of Staphylococcus epidermidis pneumonia Common symptoms Bacteremia sepsis granulocytopenia
Compared with Staphylococcus aureus, CNS does not produce alpha-toxin or toxic shock syndrome toxin. Because it does not contain superantigen, SE has less virulence factors than Staphylococcus aureus, rarely causes acute outbreaks, and SE is a premature infant. The main pathogen of sepsis after 18 hours of birth, the incidence of sepsis is significantly related to pregnancy and neonatal birth weight. People with neutropenia, especially leukemia, have about one-third of SE sepsis, and their infections are Related to the reduction of opsonophagocytosis, many acute clinical infections caused by SE, such as endocarditis caused by heart valve repair, cerebrospinal fluid drainage caused by ventriculitis, about one-third of cases continue to have SE, Lin et al reported 1995 In the two years after the year, 61 cases of pneumonia were obtained in the hospital, 56 cases were positive (91.8%), 41 were Gram-negative bacilli, and the highest infection rate was Pseudomonas aeruginosa (20/56, 35.7%), 11 strains. For Staphylococcus epidermidis (11/56, 19.6%), patients had fever, 53 (87%) above 38 °C, 57 (93%) with sputum, 51 (84%) with cough and cough, peripheral blood leukocytes > 10 × 109 / 144 cases (72%).
Examine
Examination of Staphylococcus epidermidis pneumonia
Peripheral blood leukocytes >10 × 109 / L.
Intradermal test of phytohemagglutinin: The method of specific binding of phytohemagglutinin to CNS surface carbohydrate residues improves the typing rate of CNS. The method is simple, inexpensive, and reproducible. If combined with other methods, it can be improved. The typing rate of CNS.
Diagnosis
Diagnosis and identification of Staphylococcus epidermidis pneumonia
The lower respiratory tract infection pathogens must be followed by the same principle, SE is no exception, SE is pure culture or 2 times for the same strain, useful for diagnosis, but the lack of specificity of pneumonia caused by SE, plus more mixed There is infection, so it is necessary to be cautious in determining SE culture positive. Wang et al reported 70 cases of blood culture CNS positive, only 37 cases were bacteremia, and the rest were contaminated specimens. 15 cases of invasive portals in 37 cases (40.5%) were venous cannula and artificial device, 8 cases (21.6%) were postoperative wound infection, 4 cases were respiratory tract, 4 cases were umbilical cord, 1 case was ophthalmology, 5 cases were unknown, and blood culture was judged. The sputum culture is more rigorous. Jarl reports that the phytohemagglutinin specifically binds to the CNS surface carbohydrate residue method to improve the CNS typing rate. The method is simple, inexpensive, and reproducible. If combined with other methods, it is better. Increase the typing rate of the CNS.
Must be distinguished from Staphylococcus aureus.
