2 English references to cure Staphylococcus
3 Staphylococcus aureus The biological characteristics of Staphylococcus aureus are spherical, with a diameter of 0.48 microns, arranged in grape clusters, without flagella and spores, and most of them have no capsule. A large amount of phosphomuramic acid in the cell wall of Staphylococcus aureus constitutes the surface antigen of bacteria, which is connected with muramic acid in mucin layer through valence bond of * * *. There is also muramic acid outside the cell membrane, which is of great significance for maintaining the stability of cell membrane and activating cell membrane enzymes. The cell wall can withstand 25 atmospheres.
The specificity of Staphylococcus aureus phage typing is not high, because most strains can react with more than two phages.
There is a protein component on the surface of Staphylococcus aureus, called staphylococcal protein A(SPA), which binds to the mucin part of the cell wall. About 30% of them are produced in the logarithmic growth period of Staphylococcus aureus division. If the cell wall is treated with trypsin, the activity of SPA will be destroyed. SPA can inhibit the phagocytosis of Staphylococcus aureus and Escherichia coli in vitro. Damage to platelets; There are still differences on whether human T and B lymphocytes can promote mitosis. SPA also affects the adsorption of bacteriophages by Staphylococcus aureus, and its content is negatively correlated with the number of bacteriophages adsorbed, and the strain with low SPA content has great ability to adsorb bacteriophages.
The nutritional requirements of Staphylococcus aureus are not high, and it grows well after 24 ~ 48 hours on ordinary agar medium at 37℃ and pH7.4. Staphylococcus aureus grows best under the conditions of oxygen, CO, 22℃ and cream, and the colonies produced on blood agar plate are large, and most of them can see hemolytic rings around the colonies. Staphylococcus aureus has strong resistance to spore-free bacteria and can survive for 3 ~ 6 months on dry clothes. Bacteria can still be cultured in dry sputum after 2 ~ 3 months. Staphylococcus aureus grows well in 10 ~ 15% NaCl solution. Pure culture can tolerate 1% phenol solution 15 minutes, and increasing the concentration to 2% can kill Staphylococcus aureus. The bacteria can be killed at 80℃ for 30 minutes, but Staphylococcus aureus is very sensitive to gentian violet, and the serum medium containing gentian violet 1: 125000 (concentration) can inhibit its growth.
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Variation of Staphylococcus aureus can occur naturally, but the clinical relationship may be drug sensitivity variation and colony L-form variation. There are also strains resistant to penicillin, oxacillin (new penicillin), cefazolin and other drugs. These strains, also known as methicillin-resistant Staphylococcus aureus (MRSA), pose a threat to hospital infection control. There are two ways to produce drug resistance:
① Produce inducible enzymes, such as β-lactamases, to decompose effective genes in antibiotics.
② Sensitive strains acquired drug resistance through plasmids related to phage transduction of drug resistance genes.
Another variant of Staphylococcus aureus is Staphylococcus aureus L-form isolated from some chronic or recurrent infections. These variants can not be detected by conventional methods, but can only be obtained by special culture medium and prolonged culture time. Therefore, if the culture of Staphylococcus aureus is clinically suspected to be negative, it is necessary to consider whether it mutates into L-form.
5 The laboratory test of Staphylococcus aureus mainly includes the following contents:
① Direct smear. Take a smear sample and examine it under a microscope after Gram staining.
② Culture and identity. The specimens were inoculated on blood agar plate, mannitol and high salt medium, and identified according to colony characteristics and biochemical reaction. The main characteristics of pathogenic Staphylococcus aureus are lutein production, hemolysis, mannitol fermentation, coagulase test positive, skin necrosis and animal lethal test positive. Regarding the drug sensitivity test of Staphylococcus aureus, the paper bacteriostatic ring method is commonly used in clinic, and there are also methods to determine penicillinase, but it is complicated and not used as a routine application.
③ Serological examination. Convective immunoelectrophoresis and passive gel diffusion methods can be used to detect the antibodies to muramic acid phosphate in patients' serum. Normal people have low titer and low positive rate. The antibody titer of muramic acid phosphate in the serum of Staphylococcus aureus infected patients was ≥ 1: 4. Detection of Staphylococcus aureus antigen by convection immunoelectrophoresis is helpful for early diagnosis. Antigens can be found in cerebrospinal fluid and pleural effusion, but few reports have been found in blood.
④ Toxin test. Animal experiments were carried out with kittens or monkeys, and the residual food containing toxins was injected into the stomach, abdominal cavity or vein to observe whether the animals had nausea, vomiting, diarrhea, chills and other reactions, or serological tests such as immunoagar diffusion method, indirect hemagglutination method and reverse indirect hemagglutination method, immunofluorescence method and radioimmunoassay were used to detect the content of enterotoxin in food.