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1、Chapter 10 Enteric bacilli,Outline,General properties of enteric bacilli Escherichia（埃希菌属） Shigella（志贺菌属） Salmonella（沙门菌属）,Morphology Gram-negative Rod shaped (bacilli) Most form pili and peritrichous flagella (周鞭毛) Do not form spores Culture characteristics Facultative anaerobes (兼性厌氧) or aerobes (
2、需氧) Grow readily on simple media. Colonies: circular, convex, smooth Blood agar plate: some can form hemolytic zones. Liquid media: turbid.,Biochemical reactions Catalase（触酶）test: + Reduce nitrate (硝酸盐) to nitrite (亚硝酸盐) Oxidase (氧化酶) test: - Lactose fermentation test (乳糖发酵试验)乳糖发酵试验可用于初步鉴别肠道致病菌和非致病菌
3、 肠道致病菌多数不发酵乳糖（沙门菌、志贺菌） 肠道非致病菌多数发酵乳糖（埃希菌）,Antigens O antigens: LPS, IgM H antigens: flagellin, IgG Capsular antigens: type specific, Vi antigen and K antigen. Resistance: relatively weak Variation,Gram-negative rod-shaped bacilli,MacConkey agar,A culture medium designed to grow Gram-negative bacteria
4、 and stain them for lactose fermentation. It contains bile salts (to inhibit most Gram-positive bacteria, except Enterococcus and some species of Staphylococcus), crystal violet dye (which also inhibits certain Gram-positive bacteria), neutral red dye (which stains microbes fermenting lactose), lact
5、ose (乳糖) and peptone (蛋白胨).,Macconkey agar with lactose(left) and non-lactose(right) fermenters.,Smooth,Rough,H O,Section 1 Escherichia (埃希菌属) E. coli,E. coli,Biological characterization Pathogenesis and syptomatology Pathogenic substances Clinical findings Laboratory diagnosis Treatment,Morphology
6、Gram-negative Rod shaped (bacilli) Most form pili and peritrichous flagella (周鞭毛) Do not form endospores Culture characteristics Facultative anaerobes (兼性厌氧) Liquid media: turbid. Grow readily on simple media. Colonies: circular, convex, smooth.,Biochemical reactions Lactose fermentation test (乳糖发酵试
7、验): (SS agar, KI agar) H2S test: - Motility test: + IMViC tests: + + - - Antigens: O antigens: 170 types H antigens: 50 types K antigens: 100 types,Gram-negative rod-shaped bacilli,SS agar (Salmonella Shigella agar),Ingredients:Nutrient agar 100mlLactose (乳糖) 1.00gBile salts 0.85g inhibitorSodium ci
8、trate 0.85g inhibitorSodium thiosulfate 0.85g10% ferric citrate 1ml1% Neutral red 0.25ml indicator1%brilliant green 0.033ml inhibitor,Escherichia coli on SS agar (pink colony),Kligler Iron Agar (KI agar),Ingredients:Peptones 2.00 gNaCl 0.50gGlucose 0.10gLactose 1.00 gFerrous sulfate 0.05gSodium thio
9、sulfate 0.075gAgar 0.50g0.2 phenol red 1.25mlDistilled water 100ml,Slant,Butt,In acid condition: yellow In base condition: red,Reading results of KI agar,(sulfureted hydrogen),2- Shigella 3- Salmonella 4-E.Coli,Motility test,The test is based on the flagellum of the bacteria. If the bacteria have fl
10、agellum, the semisolid medium will be clouding and the test will be positive.,Semisolid medium,E. coli,SS agar: reddish colony KI agar: yellow slants and butts,bubble in the bottom, the line of inoculation is blurryno H2S Semisolid: turbid growth, with flagella,Indole tests,色氨酸,吲哚,对二甲基氨基苯甲醛,玫瑰吲哚,+,E
11、. coli,Methyl red tests,某些细菌在糖代谢过程中，分解葡萄糖产生丙酮酸，丙酮酸可进一步分解，产生甲酸、乙酸、乳酸等，使培养基的pH降至4.5以下，当加入甲基红试剂则呈红色，为甲基红试验阳性。 若细菌分解葡萄糖产酸量少，或产生的酸进一步转化为其他物质（如醇、酮、醚、气体和水等），则培养基的酸度仍在pH6.2以上，故加入甲基红指示剂呈黄色，是为阴性。,Voges-Proskauer test,某些细菌在葡萄糖蛋白胨水培养基中能分解葡萄糖产生丙酮酸，丙酮酸缩合，脱羧成乙酰甲基甲醇，后者在强碱环境下，被空气中氧氧化为二乙酰，二乙酰与蛋白胨中的胍基生成红色化合物，称V-P（+）反应
12、。 大肠埃希菌V-P试验阴性，产气肠杆菌V-P试验阳性。,Citrate utilization test,以枸橼酸钠为唯一碳源、PH值7.0的培养基上，产气杆菌分解枸橼酸钠产生碳酸盐，使培养基由中性变为碱性，培养基中指示剂溴麝香草酚蓝（BTB）由浅绿色变为深蓝色，此为枸橼酸盐利用试验阳性。大肠杆菌因不能利用枸橼酸盐，此试验为阴性反应。,Adhesins Exotoxins Other virulence factors Endotoxin Capsules Type secretion systems,Pathogenic substances,Adhesins（黏附素）,Function:
13、 facilitate the specific adherence. Several types: Colonization factor antigen, CFA/（定植因子抗原,） Aggregative adherence fimbriae, AAF/（集聚黏附菌毛和） Bundle forming pili, Bfp（束形成菌毛） Intimin（紧密黏附素） P pili（P菌毛）,Exotoxins（外毒素）,Shiga toxins (Stx-1, Stx-2)（致贺毒素和） Heat stable enterotoxins (STa, STb)（耐热肠毒素a和b） Heat
14、labile enterotoxins (LT-,LT-)（不耐热肠毒素和 ） Hemolysin（溶血素A）: uropathogenic E. coli (UPEC),Clinical findings,Extraintestinal infections（肠道外感染） Septicemia（败血症） Meningitis of newborn（新生儿脑膜炎） Urinary tract infection (UTI)（泌尿道感染）- UPEC, urophathogenic E. coli（尿路致病性大肠埃希菌） Intestinal infections（胃肠炎）- Diarrhea-
15、causing E. coli,Diarrhea-causing E. coli,ETEC: enterotoxigenic E. coli 肠产毒型大肠埃希菌 “Travelers diarrhea” & Childrens diarrhea Watery diarrhea without blood Self-limiting (34 days) EIEC: enteroinvasive E. coli EPEC: enteropathogenic E. coli EHEC: enterohemorrhagic E. coli EAEC: enteroaggregative E.coli,
