Formerly known as Clostridium welchii orClostridium perfringensClostridium perfringensGas gangreneClostridium, the most common pathogen, can decompose muscle andconnective tissueSugar in, producing a large amount of gas, causing serious tissue damageEmphysema, and then affect the blood supply, resulting in a large area of tissuenecrosis, plus the bacteria can form in the bodyCapsule, hence the name Clostridium perfringens.
human beingsGas gangreneThe main pathogenic bacteria.In 1892, American pathologist WH. Welch and others separated this bacterium from a corpse, so it is also called Clostridium westermani.The cell is large, with a size of (0.9~1.3) × (3.0~9.0) μ m, withoutFlagellum, with capsule.SporeOval, located at the secondary end.Anaerobic is not strict.colony of bacteriaDiameter 2-5mm,Blood agar plateThere is a hemolytic circle on it.Strong sugar fermentation capacity, acid and gas production.One of the characteristics of this bacterium is thatculture mediumIt shows violent fermentation.There are 12 kinds of toxic substances that can damage the cell membranevascular endothelial cellAnd decomposes sugars, leading toCell necrosis, tissue edema, inflation and other lesions.According to the type of toxin produced and the pathogenicity, this bacterium has 6 types: A, B, C, D, E, and F.Some strains produce enterotoxin, which can causefood poisoning。G+C in DNAMoleThe content is 24-27%.This bacterium widely exists in soil, human and animal intestines, as well as animal and human feces, and will give off odor.It is often infected by deep trauma.causeGas gangreneThe pathogenic bacteria include Clostridium norvegicum, Clostridium putrescens, Clostridium histolyticum, Clostridium sporogenes, etc.In addition, Clostridium perfringens can cause dysentery andcalf, piglets, rabbitschickWaitingNecrotizing enteritis；Clostridium norvegicum causes infectious gangrenous hepatitis in sheep and cattle;Clostridium putrescens causes intestinal gangrene "braxy" in cattle, sheep, pigs and other domestic animals;Clostridium shawii causes emphysema and gangrene in cattle and sheep.[1]
Morphology and dyeing
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Clostridium perfringens form Gram staining, X1000
Gram positive bacteria are short and largebacillus, size (1~1.5)μm×（3~5）μm。Both ends are blunt, single or double arranged, and occasionally chain shaped.SporeOval shape, located in the center or sub extreme of the cell, with spore diameterNot greater thanThe mycelium is not easy to form spores in general culture, but it is beneficial to form spores in sugar free medium.In the body can produce obvious capsule, no flagella, unable to move.[1]
Cultivation characteristics
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Although this fungus belongs toAnaerobic bacteriaHowever, the requirement for anaerobic degree is not too strict, and it can grow even in the environment of EH=200-250mv.
In normalculture mediumIt can grow. If glucose and blood are added, it will grow better.The suitable temperature for growth is 37-47 ℃. Most people think that 43-47 ℃ is the most suitable temperature for the growth and reproduction of this bacterium. The time of subculture is only 8 minutes under the appropriate conditions. The high temperature rapid culture method can be used to selectively isolate this bacterium. If the temperature is 45 ℃, it is easy to obtain the strain by breeding once every 3-4 hoursPure cultureA large amount of gas is produced in the deep glucose agar, causing the agar to break.
stayPork cooking mediumAfter several hours of medium culture, the growth can be seen, and a large amount of gas will be produced. The meat dregs or meat pieces will become slightly pink, but will not be digested.
It can be seen after incubating on ordinary agar plate for about 15 hourscolony of bacteriaThe diameter of colony after 24 hours of culture is 2-4mm, round, convex, smooth, translucent, with neat edges and noswarming growth phenomenon 。
On the blood plate, mostStrainsThere are double hemolytic rings, and the inner ring is completely hemolytic becauseθEffect of toxin;Incomplete hemolysis of the outer ring is caused byαToxin.
It can be decomposed in milk culture mediumlactoseIt produces acid, coagulates casein, and produces a large amount of gas at the same time. It flushes the solidified casein into a honeycomb, pushes the vaseline layer on the liquid surface upward, and even breaks the cotton plug at the pipe mouth. It is fierce, called "stormy fermentation", which is the characteristic of this bacterium.[1]
Biochemical characteristics
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All strains can ferment glucosemalt dust、lactoseAnd sucrose, producing acid and gas.No mannitol fermentation orSalicin；Liquefied gelatin produces H2S and cannot digest coagulated protein and serum,Indole negative。The main metabolites are acetic acid and butyric acid, sometimes formedbutanol。
Typing
Produced according to this bacteriumExotoxinAccording to the different species, Clostridium perfringens can be divided into five toxin types: A, B, C, D and E.Among type 5, type A and type C are the most common, causingGas gangreneAnd gastroenteritisfood poisoning；Type C can causeNecrotizing enteritis。[1]
Pathogenic conditions
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Pathogenic conditions and all parts of the countryClostridium tetanusbe similar.Clostridium perfringens can produce strongExotoxinIt also has a variety of invasive enzymes and capsules, which constitute its strong invasiveness, causing infection and disease.Although the toxin is not as toxic asBotulinum toxinandTetanus toxinStrong, but there are many kinds of exotoxinsα、β、γ、δ、ε、η、θ、ι、κ、λ、μ、ν12 kinds, andToxic effectA variety of enzymes, such asLecithinase、Cellulase、Hyaluronidase、collagenaseAnd dna enzyme, etc., constitute a powerful invasive force.Clostridium perfringens can be divided into five types: a, b, c, d and e according to the types of exotoxins produced by bacteria.It is mainly type A that causes disease to peopleGas gangreneandfood poisoning。Type c causesNecrotizing enteritis。In various toxins and enzymesαToxins are the most important,αToxin is a kind of lecithinase, which can decompose lecithin. Human and animal cell membranes are complex of phospholipid and protein, which can be destroyed by lecithinaseαToxin can damage the cell membrane of various cells, cause hemolysis, tissue necrosis, vascular endothelial cell damage, increase vascular permeability, and cause edema.In addition,θToxin has the function of hemolysis and destruction of white blood cells. Collagenase can decompose muscle and subcutaneous collagen tissue, causing tissue disintegration. Hyaluronidase can decompose interstitial hyaluronic acid, which is conducive to the spread of lesions.This bacterium can cause many human diseases, the most important of which isGas gangrene。[1]
Disease caused
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1. Gas gangrene: 60%~80% of cases are caused by type A, but in addition to Clostridium perfringens, at least five other Clostridium species can also cause gas gangrene.The disease is mostly seen in war injuries and earthquake disasters, as well as in work-related injuries and traffic accidents that usually cause extensive injuries.Pathogenic conditions andClostridium tetani be similar.
The incubation period of gas gangrene is short, usually only 8~48 hours. The bacteria produce a variety of toxins andInvasive enzyme, destroy tissue cells, ferment sugars in muscles and tissues, produce a lot of gas, causing emphysema;At the same time, the permeability of blood vessels increases, water seepage, local edema, and then squeeze the soft tissue and blood vessels, affecting the blood supply, causingTissue necrosis。In severe cases, tissue swelling and pain are severe, moisture is mixed, hair twirling is felt when touching, and a large number of tissue necrosis and odor are finally produced.Toxins produced by bacteria and toxic products of tissue necrosis are absorbed into the blood, causingToxemia、shockThe mortality rate is as high as 40%~100%.
2. Food poisoning: food poisoning caused by this bacterium is caused by ingestion of food (mainly meat food) contaminated by a large number of bacterial propagules (10 ^ 8~10 ^ 9).The incubation period is about 10 hours, and the clinical manifestations are abdominal pain, abdominal distention, watery diarrhea;No fever, nausea and vomiting.Self healing after 1~2 days.Diagnosis is often difficult without bacteriological examination.[1]
