Staphylococcus is a groupGram-positive cocci , which is named because it is often stacked into clusters of grapes.Most are notpathogenic bacteriaA few can cause disease.Staphylococcus is the most commonPyogenic coccus, is an important source of hospital cross infection, with a diameter of about 0.8 μ m, small sphericalLiquid mediumOfthe beginning stageIn culture, bacterial cells are often scattered and exist alone.
StaphylococcosisMainly byStaphylococcus aureusCaused bypoultryAcute or chronicInfectious DiseasesIn clinical practice, it often presents multiple types, such asarthritis、Tenosynovitis, foot pad swellingOmphalitisandGrapeCoccalsepticemiaWait, herePoultry industryCause great losses.The typical staphylococci of the pathogen are round or oval, often arranged in a grape shape,Gram staining positive, no flagella, noCapsule, not generatedSpore, in normalculture mediumGood growth.Staphylococcus is widely distributed in nature. Staphylococcus exists in the skin, feathers, eyelids, mucous membranes and intestines of healthy birds. At the same time, it is also a common microorganism in the environment of poultry incubation, feeding and processing.
Staphylococcus isKoch (R. Koch. 1878), L. Pasteur (1880) and A. Og ston (1881) fromPurulent fluidIt is F. J. Rosenbach (1884) who discovered in, but studied in detail through pure culture.Staphylococcalcell wallDetachedProtein AAccessibleimmunoglobulin(MainlyIgG）Specific binding, which was discovered by K. Jensen (1959), has been applied to variousimmune reaction。
Germ classification
Announce
edit
StaphylococcalRepresentative speciesyesStaphylococcus aureus(Staphylococcus aureus) (yellow)Staphylococcus albus(S.albus) (white)LemonStaphylococcus (orange), etc.S. Aureus is of various abscessesPathogen, S.albus and S.citreus are semi saprophytic on human health surface.Because in commonGravyculture mediumIt can be well developed, so the culture is relatively simple, but it is just separated from animalsamino acidandgrowth factorHigh requirements, especially fornicotinic acid、ThiamineThe requirements of are more obvious.Many species between S.aureus and S.albus have been found in nature.
The bacteria are toxic and commoninnutritionBecomes secondary whenMicrofloraThe main bacteria.Poisoning caused by the corruption of dairy products and meat is believed to be caused byBacteroidThe reason is that Staphylococcus can produceenterotoxin（enterotoxin）。This toxicbiological activityIt can stimulateVomiting centerIt produces emetic effect.However, the type similar to human skin abscess is not easy to occur in animals, and only a few can occur inAnthropoid apeSimilar symptoms occurred with rabbits.
Biological characteristics
Announce
edit
Morphological staining
Spherical or slightly elliptical, with a diameter of about 1.0um, arranged in grape shape.Staphylococcus has no flagella and cannot move.nothingSpore, generally not formed except for a few strainsCapsule。Easily usedalkaline dyeto color,Gram stainingIs positive.Its aging, death orwhite blood cellAfter phagocytosis, and some drug-resistant strains can be dyed Gram negative.
Culture characteristics
Staphylococcus aureus Gram staining
The nutritional requirements are not highculture mediumIt grows well onglucoseIt grows better in the medium ofObligate anaerobic。It can grow at 28~38 ℃,pathogenic bacteriaOptimum temperature37 ℃,PH4.5~9.8, the most suitable is 7.4.stayBroth culture mediumin24 hoursThen it grows evenly and turbidly, forming a round bulge on the agar plate, with neat edges, smooth and wet surface,OpaqueOfcolony of bacteria。Different strains of bacteria produce different pigments, such as golden yellow, whiteLemon。The pigment isLiposolubility。Staphylococcus inBlood agar plateThe colony formed on the top is large, and some strains form an obvious completely transparent hemolytic ring around the colony（β-hemolysis）There are also people who do not have hemolysis.Most hemolytic strains havePathogenicity。
biochemical reaction
Most staphylococci can decompose glucosemalt dustandsucrose, producing acid but not gas.Pathogenic strains can decomposemannitol。
Classification and typing
Staphylococcus epidermidis
according tobiochemical reaction Different from producing pigment, it can be divided intoStaphylococcus aureus（Staph.aureus）、Staphylococcus epidermidis(Staph. epidermidis) and Staphylococcus saprophyticus.Staphylococcus aureus is mostly pathogenic bacteria, and Staphylococcus epidermidis occasionally causes disease,staphylococcus saprophyticus Generally, it is not pathogenic.60%~70% Staphylococcus aureus can bephageLysis, Staphylococcus epidermidis is not sensitive.Phage can be used toStaphylococcus aureusThey are divided into 4 groups and 23 types.enterotoxintypefood poisoningIt is caused by group III and IV Staphylococcus aureus, and group II bacteria produce antibioticsDrug resistanceOfSpeed ratioGroups I and IV are much slower.causenosocomial infectionThe serious epidemic strains are 52, 52A, 80 and 81 strains in group I.causeherpesSex andExfoliative dermatitisThe most common strain is group II 71.
Antigenic structure
Staphylococcus A protein
The structure of staphylococcal antigens is complex, more than 30 kinds have been found, and only a few of their chemical composition and biological activity are known.
2．Polysaccharide antigenIt has group specificity and exists in the cell wall, so it can be grouped. The chemical composition of group A polysaccharide antigen body isPhosphoteichoic acidN-acetylglucosamine ribol residue in.The chemical composition of group B is N-acetylglycosaminoglyceride residue in phosphoteichoic acid.
3. The capsule antigen is found on the surface of almost all Staphylococcus aureus strainsCapsular polysaccharideThe presence of antigens.Only a few strains of Staphylococcus epidermidis have this antigen.
Pathogenicity
Announce
edit
Pathogenic substance
Staphylococcus aureus produces various toxins and enzymes
Staphylococcus aureus septicemia
1．Plasma coagulase(Coagulase) can makeCitric acidSodium orheparinAnticoagulantIt is an enzyme substance that coagulates human or rabbit plasma and can produce pathogenic bacteria. It is often used to identify whether there is staphylococcusPathogenicityImportant signs of.CoagulaseThere are two kinds: one is secreted to the outside of the bacteria, which is called Free Coagulaseprotein。Similar functionprothrombinSubstance that can be activated by cofactor in human or rabbit plasma to becomethrombinAfter the sample, make the liquidFibrinogenBecome solidfibrinTo coagulate the plasma.Another kind of coagulase binds to the cell surface and does not release, called Bound Coagulase or Chumming factor. It acts as a specific receptor for fibrinogen on the surface of the strain. When the bacteria are suspended in human or rabbit plasma, fibrinogen and the cell receptor are cross-linked to make the bacteria coagulate.Free coagulase was detected by tube method, and combined coagulase was detected by slide method.Coagulase is heat-resistant, and the crude product is 100 ℃ for 30 minutes orAutoclaveIt still retains some activity after treatment, but is easily covered by proteinCatabolic enzymedestruction.
CoagulaseStaphylococcalvirulenceClose relationship.After coagulase positive strains enter the body, fibrin in blood or plasma will be deposited on the surface of the cell, which will hinder the bodyPhagocyteEven if swallowed, it is not easy to be killed.At the same time, coagulase gathers around the bacteria, which can also protect the bacteria from the bactericidal substances in the serum.The infection caused by staphylococcus is easy to be localized and form thrombus, which is related to the production of coagulase.
Coagulase hasImmunogenicityAntibodies that stimulate the body to produce have a certain protective effect on coagulase positive bacterial infection.Chronic infectionPatient serum may haveCoagulaseThe presence of antibodies.
2. StaphylococcushemolysinMost pathogenic staphylococci produce hemolysis, etc.PressantigenicityDifferent, there are at least five kinds of α, β, γ, δ and εPathogenicityα hemolysin is the main factor of α hemolysin.It is an "attack factor",chemical compositionIt is a protein with a molecular weight of about 30000. It is heat resistant and can be destroyed at 65 ℃ for 30 minutes.If α - hemolysin is injected into animal skin, it can cause skin necrosis, such asintravenous injection, the animals will die quickly.Alpha hemolysin can also makevasoconstriction, resulting inLocal ischemiaAnd necrosis, and can causesmooth muscle spasm 。Alpha hemolysin is aExotoxin, with good antigenicity.throughformaldehydeProcessing can be made intotoxoid。
4．enterotoxin(Enterotoxin) clinically isolatedStaphylococcus aureusAbout 1/3 of them produce enterotoxin according to antigenicity andIsoelectric pointAnd so on,Staphylococcal enterotoxinDivided into A, B, C1, C2C3Eight serotypes, D, E, and F (the serotype F has been canceled, because in fact, type F enterotoxin is TSST1),Bacterial energyProduce one or more types of enterotoxin, and the enterotoxin is singlePolypeptide chain, containing moreLysine、Tyrosine、Aspartateandglutamate。Enterotoxins can causeAcute gastroenteritisI.efood poisoning。Contaminated milk, meatFish isShrimp, eggs and other foods can produce a large amount of enterotoxin after 8-10 hours at 20 ℃ or above.Enterotoxin is asoluble protein , heat-resistant, not damaged or damaged after boiling at 100 ℃ for 30 minutesTrypsinTherefore, after ingesting the food contaminated with enterotoxin by mistake, it acts on the internal fat in the intestineNeuroreceptors, afferent center, stimulationVomiting center, causing vomiting and acute gastroenteritis.The onset is acute, the course of disease is short, and the recovery is fast.commonlyincubation period1~6 hoursdizzyVomiting and diarrhea, which can recover on their own within 1 to 2 days after onset, and recover well.
5．Epidermolytic toxin(Epidermolytic toxin)Epidermal exfoliationToxin (Exfoliatin) causes human or new lifemiceExfoliative lesions of the epidermis.It mainly occurs in neonates and infants, leading toScald like skin syndrome。Mainly byphageType II goldGrapeThe produced protein, with a molecular weight of 24000, has antigenicity and can be detoxicated into toxoid by formaldehyde.
6. Toxic shock complex toxin I(Toxic shock syndrome toxin 1, TSST1) is produced by Staphylococcus aureus phage group I.May causefever, add pairendotoxinOfsusceptibility。enhanceblood capillarypermeability, causing vascular disorder and shock.
7. Other staphylococci can be producedStaphylokinaseStaphylokinaseCellulase(Staphylococcal fibrolysin) to produce heat resistant nuclease (Heat-stablenuclease)，Hyaluronidase(Hyaluronidase), Lipase, etc.
2. Toxic diseases are caused by related exotoxins produced by Staphylococcus aureus.
(1) Food poisoningSymptoms such as nausea, vomitingabdominal painDiarrhea, most patients recover within a few hours to 1 day.
(2) Scald like skin syndromeMore common in newborns, young children andLow immune function20% of adults begin to have erythema, skin wrinkling in 1~2 days, and then formBlister, till the epidermis falls off.It is caused by epidermal lysotoxin.
（3）Toxic shock syndromeCaused by TSST1, mainly shown asHigh fever、hypotension, Erythema rash withDesquamationAnd shock, more than half of the patients have nausea, diarrheaMyalgiaCongestion of conjunctiva and mucosa, damage of liver and kidney functions, and occasional cardiac involvement.
（4）PseudomembraneInflammatory enteritis is a kind ofDysbacteriosis enteritisThe pathological feature is that the intestinal mucosa is covered by a layer of inflammatory pseudomembrane, which is composed of inflammatory exudate, intestinal mucosal necrosis block and bacteria.About 10-15% of the population has a small amount of Staphylococcus aureus living in the intestinal tract. When the dominant bacteria such asBacteroides fragilis, Escherichia coli, etcAntibacterialsWhen the drug resistant Staphylococcus aureus is inhibited or killed due to the application of antibiotics, it will take the opportunity to reproduce and produce toxins, causing clinical symptoms mainly diarrhea.
Immunity
Human beings have certain natural immunity to pathogenic staphylococcus.Only whenSkin mucosaIt is easy to cause infection after trauma or when the body immunity is reduced.The acquired immunity after illness is not strong, and it is difficult to prevent re infection.
Microbiological diagnosis
Announce
edit
Different disease typesInspection materialSuch as pus, blood, suspicious food, vomit and feces.
Direct smear microscopy
Take samplessmear，Gram stainingThe initial diagnosis can be made according to the morphology, arrangement and staining of the bacteria by means of posterior microscopy.
Isolation culture
staphylococcus
Inoculate the specimen onBlood agar plate，mannitolAnd high salt mediumIsolation culture, select coagulable after incubationcolony of bacteriaSmear, stain and microscopic examination shall be performed.Main characteristics of pathogenic staphylococcus:CoagulaseIt produces positive, golden yellow pigment, hemolytic, and ferments mannitol.
The vomit, feces or residual food of food poisoning patients shall be inoculated into theBroth culture mediumAfter incubation, the filtrate was taken and injected into the abdominal cavity of 6-8 week old kittens. Vomiting, diarrhea, temperature rise or death occurred within 4 hours after injection, indicating the possibility of enterotoxin.
