It is a bacterium with low pathogenicity but strong drug resistance. Widely distributed in nature, it is a common bacterium of wound infection. Can cause purulent lesions. The pus is green, hence the name.
Pseudomonas aeruginosa belongs to the genus Pseudomonas, which is widely distributed in the skin, intestine and respiratory tract of nature and normal people. It is one of the common conditional pathogens in clinic. The size is 1.5 ~ 3.0× 0.5 ~ 0.8 um, g- bacilli. Bacteria usually have flagella at one end, which is very lively. Rice liquid strain has no spore, polysaccharide capsule or sugar calyx, and has anti-phagocytosis effect. It grows well on ordinary culture medium and needs oxygen. Colonies have different shapes, most of which are 2 ~ 3 mm in diameter, with uneven edges, flat and moist. Transparent hemolysis ring was formed on blood agar plate. The liquid culture showed turbid growth and biofilm formation. Pseudomonas aeruginosa can produce two kinds of water-soluble pigments: one is pyocyanin, which is a blue-green phenazine compound with no fluorescence and antibacterial effect. The other is fluorescein, which is green. Pseudomonas aeruginosa is only produced by Pseudomonas aeruginosa, so it has diagnostic significance. However, the mutant strains screened after extensive use of effective antibiotics often lose their synthetic ability.
The ability to decompose protein is very strong, but the ability to ferment sugar is low. It can decompose glucose, produce acid without producing gas, liquefy gelatin without decomposing mannitol, lactose and sucrose. Urea decomposes, indole is not formed, oxidase test is positive, citrate can be used. Pseudomonas aeruginosa has bacterial O antigen and flagella H antigen. O antigen contains endotoxin and protoendotoxin protein. Protein is a protective antigen with high molecular weight, low toxicity and strong immunogenicity. It exists not only in different serotypes of Pseudomonas, but also in other bacteria of Pseudomonas and g- bacteria such as pneumonia, Escherichia coli and Vibrio cholerae. It is a good cross-protection antigen.
Pseudomonas aeruginosa can produce many toxic substances, such as endotoxin, exotoxin A, elastase, collagenase and trypsin, among which exotoxin A is the most important. Pseudomonas aeruginosa exotoxin A is a thermally unstable single-stranded polypeptide with a molecular weight of about 66,000. After being treated with formaldehyde or glutaraldehyde and neutralized with specific antitoxin, it can detoxify into toxoid. Strong toxicity, after being injected into animals, the liver of the main target organ can undergo cell swelling, steatosis and necrosis; Other organ diseases include pulmonary hemorrhage and renal necrosis. The mechanism of action of exotoxin A is similar to diphtheria toxin, that is, elongation factor 2 (EF ~ 2) on ribosome is finally inactivated, and protein synthesis of host cells is inhibited, but the specific process is different. In addition, exotoxin A and diphtheria toxin are different in protein structure, immunogenicity, whipping cells, sensitive animals and so on.
Pseudomonas aeruginosa infection can occur in any part and tissue of human body, and often occurs in burn or trauma sites, middle ear, cornea, urethra and respiratory tract. It can also cause endocarditis, gastroenteritis, empyema and even sepsis. Patients can produce specific antibodies after infection, which has certain anti-infection effect. The application of anti-Pseudomonas aeruginosa immune serum can reduce the incidence and mortality of secondary sepsis in patients.