医学微生物学课件：12 厌氧菌

1、1Anaerobes (厌氧菌)2spore-formers & non-spore formersSpore-formers (clostridium,梭状芽胞杆菌属) exotoxinscommon in the environment (e.g. soil)found in normal floraNon - spore-formersno exotoxins mostly normal flora 3Most anaerobes in the normal flora are non-spore formers and anaerobic infections often occur

2、from this source.Contamination of wounds can also occur with anaerobic spore-formers (e.g. clostridia) which are common in the environment (e.g. soil). Non-spore-formers rarely produce exotoxins in contrast to spore-formers.Endogenous vs exogenous infection(内源性感染与外源性感染）4Clostridium(梭菌属)G+ , bacilliS

3、pore-forming, wide than rod Flagella all over the bacilli (周鞭毛)(besides C. perfringens, 产气荚膜梭菌)Strict anaerobic, 5Clostridium(梭菌属)Reservoir: found in the environment (particularly soil)intestine of man and animalsPathogenicity:Exotoxins Invasive enzymes6Important pathogensC.tetani(破伤风梭菌)- tetanus(破伤

4、风)C.perfringens(产气荚膜梭菌) - gas gangrene(气性坏疽)C.botulinum(肉毒梭菌)- botulism(肉毒中毒)C.difficile(艰难梭菌) -pseudomembanous colitis(假膜性结肠炎)7Sec. 1 C. tetani (破伤风梭菌)Morphology Round spore, on the top, drumstick-like (鼓槌状)Pathogenic factorsCommonly found in the soil; thus contamination of wounds can lead to colon

5、ization and tetanus.tetanospasmin(破伤风痉挛毒素) (lethal minimum: 1mg)diseaseTetanus(破伤风)8Tetanospasmin (破伤风痉挛毒素)C.Tetani (localized infection)along nerves/blood/lymph CNSbinds to gangliosides stops the nerve impulse transmission to muscles spastic paralysis of muscles9tetanospasminThe exotoxin (tetanospa

6、smin) binds to ganglioside receptors on inhibitory neurones in CNS;Glycine is commonly the neurotransmitterExotoxin stops the nerve impulse transmission to muscles leading to spastic paralysis. Continued severe muscle contractions and spasms result which can be fatal.10甘氨酸1112opisthotonos角弓反张13Preve

7、ntion and TreatmentSpecific preventionArtificial active immunizationDPT( diphtheria, tetanus, pertussis, 白百破三联疫苗)Tetanus toxoid (破伤风类毒素)Urgent prevention and specific treatmentArtificial passive immunizationTAT( Tetani antitoxin ,破伤风抗毒素)14Sec. 2 C. perfringens (产气荚膜梭菌)morphologyoval spore, is placed

8、 subterminally Forming capsule in hostscultureStrict anaerobic, stormy fermentation(汹涌发酵)double hemolysis rings (双层溶血环)1516Pathogenicity Wound infection-gas gangrene(气性坏疽)Lecithinase (卵磷脂酶) .Without treatment death occurs within 2 daysFood poisoningEnterotoxin 8-12h，self-healing after 12dNecrotic En

9、teritis (C type )17gas gangrene18morphologyOval spore, is placed subterminally, the shape like tennis racket (网球拍状)Pathogenic factor-botulinus neurotoxins (肉毒毒素)neurotoxin, strongest (lethal minimum: 0.1mg)Heat-labile, proteinase-stable Produce by lysogenic (溶原性) C.botulinumDisease- Botulism(肉毒中毒)Se

10、c. 3 C. botulinum (肉毒梭菌)19Botulin (botulinus toxin,肉毒毒素)lysogenic C. botulinum (contaminated canned food et al)Botulin is ingested and absorbedNervous systeminhibits the release of acetylcholineat cholinergic synapses(胆碱能突触) flaccid paralysis(松弛性麻痹)death (respiratory, cardiac failure)2021The organis

11、m does not grow in the gut, but pre-formed exotoxin from prior germination of spores may be present in inadequately sterilized canned food (usually at home)Wound botulism can occur but it is rare.22In the neonate, where the flora is not established, colonization with C. botulinum can occurInfant bot

12、ulism, although uncommon, is now the predominant form of botulismTreatment includes administration of anti-toxin and (for neonates) antibiotic therapy23C. Difficile (艰难梭菌）When the normal flora of the intestine is altered by antibiotic therapy this organism can colonize. It produces an enterotoxin an

13、d pseudomembanous colitis can result. Therapy includes discontinuation of the implicated antibiotic (e.g. ampicillin). Severe cases require specific antibiotic therapy (e.g. with vancomycin).24Clostridia The clostridia are large anaerobic, gram-positive, motile rods. Many decompose proteins or form

14、toxins, and some do both. Their natural habitat is the soil or the intestinal tract of animals and human beings, where they live as saprophytes. Among the pathogens are the organisms causing botulism（肉毒中毒）, tetanus（破伤风）, gas gangrene（气性坏疽）, and pseudomembranous colitis（伪膜性肠炎）.25Non-Spore-Forming Ana

15、erobes (Non - spore-formers, 无芽胞厌氧菌)1.G- rods拟杆菌属, 普雷沃菌属, 梭杆菌属2.G+ rods双歧杆菌属, 丙酸杆菌属, 乳杆菌属3.G+ cocci 消化链球菌4. G- cocci韦荣球菌属26Primary characteristicsdistributingNormal florapathogenicityopportunistic pathogen, endogenic infection, secondary infection (继发感染)Pyogenic infection, involve whole body (累及全身任何

16、部位)Difficult to diagnose and cure27Primary characteristicsPathogenic factorsinvasivenesspili, capsule, enzymesendotoxintreatmentInefficient drugs: 氨基糖甙类/磺胺类Efficient drugs: 甲硝唑28Brief SummaryC. Tetani tetanospasmin (痉挛毒素)-TetaniC. perfringensgas gangrene/food poisoninga-toxin / lecithinase (卵磷脂酶）et

17、alenterotoxin29Brief SummaryC. botulinumbotulin (肉毒毒素)food poisoningC. difficileenterotoxin / cytotoxinpseudomembanous colitisNon-spore-Froming anaerobes normal flora, largest group?Opportunistic infection, pyogenic30Key wordsAnaerobesStrict anaerobicClostridium (pl. Clostridia)Endogenous infectionexogenous infectionC. perfringensstormy fermentationC.tetaniC.botulinumlecithinaseC.difficileTetanusgas gangre