Green forest episode 13
Green children who thought the green light was going to be turned off, as soon as they heard CEO William say that as long as they won the relay race tomorrow, the green light primary school would not be turned off. Everyone was jubilant, and William walked step by step to the trap set by the cannon. Who will sit in that chair covered with super glue?
William received the information from the best medical institution in the world and found that Sophie's disease is a kind of Pseudomonas which is difficult to cure. If Sophie is infected with the most serious drug resistance, or the antibiotics used can't kill the virus, Sophie may lose her life. Susan, who never wanted Sophie to be happy, knew Sophie's illness. Susan suddenly felt how ridiculous and outrageous her plunder and hostility to Sophie in the past 20 years was. However, such recognition will be in Susan's heart. What method will he choose to treat Sophie?
The confident green children came to Spencer College, and the relay race to defend the green light was about to begin. As we all know, if Green Capital wins, not only can Green Capital be independent of Spencer, but William will also keep his position as CEO. But if the green light loses, the green light will disappear from now on, and William will give up his post unconditionally. On the track, what unexpected things will happen when the powerful Spencer team and the green children who get along with nature all day face such great challenges? Can Green Light Primary School really win the championship smoothly?
Pseudomonas aeruginosa belongs to Pseudomonas genus of Pseudomonas family, with more than 40 species/kloc-0. Most of them are saprophytic bacteria or can cause plant diseases, and about 25 species can infect humans, but most of them are opportunistic infections. Pseudomonas aeruginosa is the most studied and important pathogen of nosocomial infection in this genus.
Because it is rod-shaped, it is classified as aerobic gram-negative rod-shaped bacteria and cocci in Berger's handbook of systematic bacteriology.
Pseudomonas aeruginosa means copper green, because most Pseudomonas aeruginosa secretes two water-soluble pigments, one is light blue pyocyanin without fluorescence, and the other is light green fluorescein, so when a wound is infected by Pseudomonas aeruginosa, blue-green pus often appears, which is the origin of the name of Pseudomonas aeruginosa.
Third, natural habitats.
Pseudomonas aeruginosa likes humid environment, so it is usually distributed in soil, water, air and plants, on the skin of some healthy people, and even in rotten food.
Four. Size and type
The size of Pseudomonas aeruginosa is about 1.5 ~ 3.0 microns long and 0.5 ~ 0.8 microns wide, which is similar to Enterobacteriaceae, but thinner and less colored. Most of them are single-ended flagella, and many strains have fimbriae or saccular outer membrane composed of alginate, which makes their colonies sticky, and this strain will not produce spores.
Pseudomonas aeruginosa can quickly grow into a smooth and round colony on the culture medium, which is caused by its secreted viscous algal polysaccharide, while the green color with fluorescence is caused by the above two water-soluble pigments, which can decompose aromatic benzene rings and produce a special aromatic smell.
According to the different growth environment, it can be divided into three different types: urinary tract and respiratory tract mucoid; The colonies separated from soil and water are small and irregular; As for clinical culture, the scale is larger and the edge is relatively flat.
V. Suitable growth environment
The most suitable growth temperature of Pseudomonas aeruginosa is 25 ~ 37℃, which is equivalent to human body temperature, so it can grow in human body, but it can still survive in refrigerator or when the temperature is as high as 42℃. The pH range of survival is pH 5 ~ pH 9, and the most suitable pH value for growth is around pH7.
As long as the humidity is appropriate, Pseudomonas aeruginosa can grow anywhere, so it is very easy to pollute medical instruments, disinfection water, respirators, medicines and so on. In hospitals, it is often spread through fruits, plants and vegetables.
In the hospital, on the liquid surface polluted by Pseudomonas aeruginosa or the wet surface of medical equipment, this bacteria will secrete a lot of alginate and connect them into a thin film, so it is not easy to be washed off; It can even prevent bactericides or antibiotics from entering bacteria, so that Pseudomonas aeruginosa can survive in high-concentration sterilized water.
VI. Cultural characteristics
Pseudomonas aeruginosa has a simple demand for nutrients, which can not only decompose and utilize a variety of organic substances, but also use simple ammonium sulfate as nitrogen source and acetate as carbon source.
If it is cultured in semi-solid medium, after inoculation with puncture technology, the diffusion mode along the inoculation line will be found, and all of them will be concentrated in the upper layer, which can prove that it has the characteristics of sports and aerobic.
Pseudomonas aeruginosa can grow for the first time in various nutrient media, with flat colonies and irregular edges, which will produce blue-green pigments, and hemolysis can be observed in blood agar media.
Because Pseudomonas aeruginosa can't ferment lactose to produce acid, colorless colonies will be produced on Maconchy agar (MCA) and eosin methylene blue agar (EMB).
Seven, biochemical characteristics
Pseudomonas aeruginosa is a gram-negative bacterium, which is absolutely aerobic, but it can also grow in an anaerobic environment, using nitrate as an electron acceptor.
This strain can't ferment, and mainly metabolizes carbohydrates by oxidation reaction. Positive oxidase test is the most commonly used test method to distinguish Pseudomonas aeruginosa from other gram-negative bacteria.
In terms of separation and purification, bacteria belonging to different species can first make a general biochemical reaction to see if fluorescein is produced, as listed in the following table; The existence of arginine biohydrolase narrows the range of possible strains, and the decisive feature of identifying Pseudomonas aeruginosa is the difference of culture temperature: among all bacteria belonging to different species, only Pseudomonas aeruginosa can still grow above 42℃, and other bacteria can't; In addition, only Pseudomonas aeruginosa can not grow below 4℃, and all other species can.
Because Pseudomonas aeruginosa doesn't require much nutrients, it can grow on general culture medium without special culture medium, so generally speaking, because the algae polysaccharide secreted by Pseudomonas aeruginosa is a sticky substance, as long as the colony with sticky surface is observed with naked eyes on the culture medium, if it is cultured on general culture medium alone, it is almost certain to be Pseudomonas aeruginosa.
The following table summarizes the important biochemical reactions of Pseudomonas aeruginosa and some identification characteristics of non-fermented gram-negative bacilli:
Page (abbreviation of page)
pseudomonas aeruginosa
Page (abbreviation of page)
luciferin
Page (abbreviation of page)
Pseudomalleus
Page (abbreviation of page)
Hammerhead (deformation of malleus)
Page (abbreviation of page)
cepacia
Page (abbreviation of page)
Maltophilia
Page (abbreviation of page)
Stuzeri
luciferin
+
+
_
_
_
_
_
Arginine biohydrolase
+
+
+
+
_
_
_
Maconchy agar
+
+
+
_
+
+
+
motive power
+
+
+
_
+
+
+
oxidase
+
+
W+
W+
+
_
+
Grow at 42℃
+
_
+
+
+/_
+/_
+/_
4℃ growth
_
+
_
_
_
_
_
Gluconic acid oxidation
+
+/_
_
_
_
_
_
glucose
+
+
+
+
+
_
+
gelatinase
+
+
+
_
+/_
_
_
W= weak; += positive; -= negative; +/_ = variable.
Eight, pathogenicity or application
According to the current literature reports, the pathogenic mechanism of Pseudomonas aeruginosa can be summarized as follows: after Pseudomonas aeruginosa invades the host through the wound or respiratory mucosa, it first adheres to the cell surface by using the cilia on the cell surface, and the cell begins to grow and reproduce, while secreting many toxins and proteolytic enzymes.
These proteolytic enzymes will destroy the tissues at the infected site to provide nutrients for the growth and division of bacteria, and at the same time, they will decompose antibacterial defense proteins such as complement, immunoglobulin or cytohormone in the host, making it difficult for the patient's immune system to play its usual defense level and destroy the invading Pseudomonas aeruginosa.
Due to the increase in the number of bacteria, the nutrients near the wound decreased. At this time, flagellated Pseudomonas aeruginosa began to move to the blood stream with sufficient nutrition supply. At this time, protein hydrolase may also be beneficial for Pseudomonas aeruginosa to penetrate the blood vessel wall and enter the blood stream to cause bacteremia.
Because Pseudomonas aeruginosa continuously secretes toxins or proteolytic enzymes, the components of cell wall endotoxin may even reach various internal organs through blood circulation. For example, protein hydrolase continuously decomposes serum proteins with immune and antibacterial effects, making the host unable to fight Pseudomonas aeruginosa. Coupled with the influence of endotoxin, the mortality rate of Pseudomonas aeruginosa infection is often as high as 70%, which is higher than other common opportunistic infections.
Pseudomonas aeruginosa can cause different diseases due to different infection routes: if the intubation equipment is polluted, it will lead to urinary system infection; Infection during spinal puncture can lead to meningitis; And because it has the function of inhibiting or destroying white blood cells, it may cause septicemia when infected by anticancer drugs or burn patients, and its mortality rate will exceed 80%, which can be said to be an extremely difficult pathogen in hospitals.
At present, hospitals use carbolic acid or glutaraldehyde to disinfect instruments that may be contaminated by Pseudomonas aeruginosa; Amikacin, gentamicin, tobramycin and colistin are widely used in the treatment, and the mixed treatment of gentamicin and carbenicillin is the most extensive and effective.
References:
Edited by Ding Mingzhe. 1996 first edition. Chapter 26, Pseudomonas and other non-fermentative bacilli. Medical microbiology. Hutchison Book Publishing House. p333~p339 .