医学微生物学英文教学课件：8 enterobacteriaceae2

1、chapter 8Enterobacteriaceae1. G- rods with similar biological properties, naturally inhabit in intestinal tract of human and animal, soil, water.2. according to pathogenicity, divided into endogenous normal flora and exogenous pathogen.3. most are normal flora of enteric tract but cause endogenous o

2、r opportunistic infections as opportunistic pathogen in the immunocompromised individual or if move to extraenteric habitats (urinogenital/biliary tract, peritoneal cavity, blood stream).4. pathogenic E.coli, shigellae, salmonellae can cause exogenous infection within enteric tract of individual. -

3、pathogens of enteric tractSection 1. Biological Properties of Enterobacteriaceae1).morphology and structure G- rods, most possess flagella and pili. No spore, certain members possessing capsule.2). culture: agar plate, smooth colony1. Common Biological Properties3).biochemical reaction - active & di

4、verse many kinds of carbohydrates and proteins can be utilized and form various products. Differentiation - Lactose fermenting bacteria enteric non-pathogens Non-lactose fermenting bacteria enteric pathogens4). antigenic structure complex(1) O antigen (specific polysaccharides of LPS) repeating sequ

5、ence of carbohydrates of different enteric bacilli varying in the constitution and arrangement - basis of serological classification (2) H Ag (flagella protein) specificity of H antigen is determined by the arrangement and stereoscopic form of amino acids within polypeptides. - basis of serological

6、classification(3)capsule Ag Polysaccharides that cover the O Ag Main capsule Ag: Vi antigen (S. typhi), K antigen (E. coli) H AgO AgK or Vi Ag5). produce endotoxin (LPS) and/or exotoxin 2. Biological Properties of E.coli result in extraenteric infection if in the immunocompromised host or move to ex

7、traenteric tissue or organ. certain strains can cause diarrhea.1. G- rods, possess flagella and pili2. common agar- smooth colony, grey-white blood agar- - hemolysis (certain strains) 3. Biochemical reaction extremely active and complex lactose fermentation “+” 4. Antigenic structure O Ag, H Ag, K A

8、g e.g. serotype is expressed as O111:K58 (B4):H2 Section 2. opportunistic pathogenic enteric bacilli1. E.coliI Pathogenisis & Clinical findings I Pathogenisis & Clinical findings 1). Extraenteric infection urinogenital tract, biliary tract, peritoneal cavity and blood stream.cause pyelonephritis, ur

9、inary tract infection (the most common ), G- bacteremia, septicemiaI Pathogenisis & Clinical findings 2). Diarrheacertain serotypes of E.coli cause human diarrhea, called pathogenic E.coli Enterotoxigenic E.coli (ETEC) 1. pathogenic factor 1). pili (adhesin, CFA (colonization factor Ag) specifically

10、 adhere to the epithelial cell of small intestine 2). enterotoxin consists of heat labile enterotoxin (LT) and heat stable enterotoxin (ST) I Pathogenisis & Clinical findings I Pathogenisis & Clinical findings LT ST heat 65 ,30min 100,30 min MW 73,000 4,0005,000 Ag AgAb nostructure 1A and 5B a and b

11、2. pathogenisis Heat labile toxin (LT)like choleragenadenyl cyclase activated cyclic AMP secretion water/ions Heat stable toxin (ST) guanylate cyclase activated cyclic GMP uptake water/ions I Pathogenisis & Clinical findings I Pathogenisis & Clinical findings I Pathogenisis & Clinical findings child

12、 (5 years), adult (traveller) watery, nonbloody diarrhea, nausea, vomit, abdominal cramps, low fever3. clinical finding Enteroinvasive E.coli (EIEC) 1. pathogenic factor 1). invasiveness 2). endotoxin 2. pathogenisis enteroinvasive, cause disease not by enterotoxin formation but by invasion of the e

13、pithelium of the large intestine. I Pathogenisis & Clinical findings I Pathogenisis & Clinical findings 3. clinical findingchild , adult bloody diarrhea (like dysentery), inflammation, abdominal cramps, fever Enteropathogenic E.coli (EPEC) 1. pathogenisis no exterotoxin, poor invasiveness adhere the

14、 epithelium of the small intestine, destroy brush border microvilli atrophy epithelial cell dysfunction severe diarrhea I Pathogenisis & Clinical findings I Pathogenisis & Clinical findings infantile enteritis, less in adultswatery diarrhea, nausea, vomit, abdominal cramps, low fever, severedeath 2.

15、 clinical finding Enterohemorrhagic E.coli (EHEC):I Pathogenisis & Clinical findings 1. pathogenic factor 1). Intimin (pili) specifically adhere to the epithelial cell of large intestine 2). Vero toxin (shiga-like toxin, SLT) enterotoxin: early watery diarrhea cytotoxin: stop protein synthesis neuro

16、toxinI Pathogenisis & Clinical findings O157:H7 bloody diarrhea, severe abdominal cramps, hemorrhagic colitis, hemolytic uremic syndrome (HUS)3. clinical finding 2. pathogenisis Vero toxin, no invasiveness I Pathogenisis & Clinical findings II Microbiologic Examination1. Specimen: feces, blood, pus

17、2. Isolation and identification: serologic identificationSanitary Significance Coliform bacteria index: the number of coliform bacteria detected out per 1000 ml sample. the standard of drinking water is less than 3.Section 3. Shigella(dysentery bacterium)1. G-, non-motile, possesses pili2. biochemic

18、al reaction lactose fermentation - negative (Shigella. sonnei - late fermentation)3. culture: common agar4. antigen: O Ag , K AgI biological properties5. classification: 4 groups, 42 serotypes StrainGroupSerotypeMannitolS. dysenteriaeA10-S. flexneriB13+S. boydiiC18+S. sonneiD1+I biological propertie

19、s6. Resistant: weak, antibiotic-resistance I biological properties1. Pathogenic factorinvasiveness pili, adhere epithelial cells of ileum end and colon mucosa II Pathogenicityinduce endocytosis; form endosomegrow and propagate within the epithelial cellsspread to tissue widely and deeplyinflammation

20、 & ulcerationShigella attachment and penetrationII Pathogenicity(2) endotoxin fever, toxic shock; inflammation, ulceration; rectal cramp, tenesmus(3) exotoxin shiga toxin (ST) A group shigella enterotoxin - early watery diarrheacytotoxin - stop protein synthesisneurotoxin2. Phathogenesis organisms o

21、ral route sudden incubation 13 days abdominal colic watery diarrhea fever, malaise local inflammation ulceration bloody mucopurulent stool, abdominal cramp, tenesmus, hemolytic uremic syndrome (HUS)II Pathogenicity3. Disease bacterial dysentery human, the natural host (sensitive) transmitted by fece

22、s mouth pathway II PathogenicityII Pathogenicity*acute dysentery fever (39), abdominal cramp, tenesmus, bloody stool toxic dysentery children, no obvious symptom of alimentary tract, system toxicosis symptom capillary spasm, ischemia, hypoxia DIC, multi-organ exhaustion, death *chronic dysentery4. I

23、mmunity SIgA1. isolation and identification stool / rectal swab selective media biochemical, serological and animal tests 2. rapid diagnosis coagglutinationIII Microbiologic Examination1. live vaccine streptomycin dependent strain, Sd2. antibiotics ampicillin, tetracycline antibiotic-resistance IV P

24、revention & TreatmentSection 4. Salmonella1. G-, peritrichous 2. grow in simple cultural media 3. biochemical reaction lactose fermentation - negative 4. antigen: O antigen, H antigen, Vi antigen (virulent Ag)I biological properties 1. Pathogenic factors (1) Invasiveness Pili - adhesion, internalization, intracelluar proliferation Vi antigen - antiphagocytosis (2) Endotoxin fever, WBC, shock (3) Enterotoxin S.typhimurium: LT/ST II Pathogenicity2. Diseases (1) Enteric fever human pathogen typhoid paratyphoid II Pathogenicity Characteristics- facultative intracell