醫(yī)學微生物學課件：12 厭氧菌

1、1Anaerobes (厭氧菌)2spore-formers & non-spore formersSpore-formers (clostridium,梭狀芽胞桿菌屬) 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(內(nèi)源性感染與外源性感染）4Clostridium(梭菌屬)G+ , bacilliS

3、pore-forming, wide than rod Flagella all over the bacilli (周鞭毛)(besides C. perfringens, 產(chǎn)氣莢膜梭菌)Strict anaerobic, 5Clostridium(梭菌屬)Reservoir: found in the environment (particularly soil)intestine of man and animalsPathogenicity:Exotoxins Invasive enzymes6Important pathogensC.tetani(破傷風梭菌)- tetanus(破傷

4、風)C.perfringens(產(chǎn)氣莢膜梭菌) - gas gangrene(氣性壞疽)C.botulinum(肉毒梭菌)- botulism(肉毒中毒)C.difficile(艱難梭菌) -pseudomembanous colitis(假膜性結(jié)腸炎)7Sec. 1 C. tetani (破傷風梭菌)Morphology Round spore, on the top, drumstick-like (鼓槌狀)Pathogenic factorsCommonly found in the soil; thus contamination of wounds can lead to colon

5、ization and tetanus.tetanospasmin(破傷風痙攣毒素) (lethal minimum: 1mg)diseaseTetanus(破傷風)8Tetanospasmin (破傷風痙攣毒素)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角弓反張13Preve

7、ntion and TreatmentSpecific preventionArtificial active immunizationDPT( diphtheria, tetanus, pertussis, 白百破三聯(lián)疫苗)Tetanus toxoid (破傷風類毒素)Urgent prevention and specific treatmentArtificial passive immunizationTAT( Tetani antitoxin ,破傷風抗毒素)14Sec. 2 C. perfringens (產(chǎn)氣莢膜梭菌)morphologyoval spore, is placed

8、 subterminally Forming capsule in hostscultureStrict anaerobic, stormy fermentation(洶涌發(fā)酵)double hemolysis rings (雙層溶血環(huán))1516Pathogenicity Wound infection-gas gangrene(氣性壞疽)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 (網(wǎng)球拍狀)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(膽堿能突觸) 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 (艱難梭菌）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（破傷風）, gas gangrene（氣性壞疽）, and pseudomembranous colitis（偽膜性腸炎）.25Non-Spore-Forming Ana

15、erobes (Non - spore-formers, 無芽胞厭氧菌)1.G- rods擬桿菌屬, 普雷沃菌屬, 梭桿菌屬2.G+ rods雙歧桿菌屬, 丙酸桿菌屬, 乳桿菌屬3.G+ cocci 消化鏈球菌4. G- cocci韋榮球菌屬26Primary characteristicsdistributingNormal florapathogenicityopportunistic pathogen, endogenic infection, secondary infection (繼發(fā)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: 氨基糖甙類/磺胺類Efficient drugs: 甲硝唑28Brief SummaryC. Tetani tetanospasmin (痙攣毒素)-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