5.2细菌的感染与免疫

nullChapter 4 Bacterial infection and immunity Chapter 4 Bacterial infection and immunity nullNormal flora and opportunistic infection Bacterial pathogenicity Process of infection Anti-bacterial immunity Nosocomial infection Normal flora and opportunistic infectionNormal flora and opportunistic infectionMicrobes and humansMicrobes and humansVery few microbes arealways pathogenicMany microbes arepotentially pathogenicMost microbes arenever pathogenicnullNormal flora Definition – bacteria, fungi, and protozoa that frequently found on or within the body of healthy persons. Composition- resident flora, transient floranullnullnullFunctions of normal flora ---- Protective effects of normal flora ---- Production of nutrients - vitamin K ---- Priming immune system - specific (natural antibodies) ---- Exclusion of pathogens from colonized surfaces nullnullnullOpportunistic infection ---- Host defenses compromised ---- Dysbacteriosis, superinfection ---- TranslocationBacterial pathogenicityBacterial pathogenicitynullnullBacterial VirulenceBacterial VirulenceInvasiveness ----surface structures of bacteria adhesin, capsule, flagellum, bacterial biofilmnull----invasive substances invasin invasive enzymes ---- immune escape incomplete phagocytosis IgA proteinase antigen variation Bacterial Bacterial Bacterial toxinsBacterial Virulence1) Exotoxins Origin: --- Produced mainly by G+ --- Liberated from living bacterial cellnullNature --- ProteinCharacter:--- Highly toxigenicity --- Highly selectivity --- Highly antigenity ,can produce anti- toxin (Neutralize) --- Detoxification toxoidnullnullnullnull①为分子量相对较大的染色体DNA片段 ②存在于强毒株 ③含编码细菌毒力及毒力相关因子的基因簇 ④两侧具有同向重复序列和插入元件 ⑤大多位于tRNA基因位点内或附近 ⑥G+Cmol%和密码子的使用与宿主菌有明显差异 ⑦ 可移动，不稳定null2) EndotoxinOrigin: Nature: --- Produced mainly by G- --- Liberated from cell wall of dead bacteria--- LPS (Lipopolysaccharide)nullStructure of LPSlipid A Core polysaccharide specific polysaccharidenull--- Weakly toxigenicity --- no selectivity --- Poor antigen as free molecule --- Having no detoxification, can not produce toxoid Character:null--- Fever --- leukocytosis or Leukopenia --- Endotoxemia and shock --- Disseminated intravascular coagulation (DIC). --- Immunregular Endotoxin effects:nullnullNumber of bacterial entry Number of bacteria and virulence present inverse proportion nullPortal entrySimple pathway Multi- pathwayProcess of infectionProcess of infectionnullInfection Sources ---exogenous infection patients ; carrier; animal ---endogenous infection normal flora; latent bacterianullTransmission and portals skin, respiratory tract, intestinal tract, urethra, vagina nullInfection types --- inapparent infection --- apparent infectionAcute infection Chronic infection Subacute infection Localized infection Systemic infection --- toxemia --- endotoxemia --- bacteremia --- septicemia --- pyemia null Components of Innate ImmunityComponents of Innate ImmunityInnate ImmunityAdaptive Immunityskin, blood-brain, blood-placentamany protein and non-protein secretionsmacrophage, NK cell Neutrophilphysical barrierssoluble factorscellsnoneImmunoglobulins (antibody)T and B lymphocytesnull 正常体液与组织中的抗菌物质null细胞核nullChemotactic response to inflammatory stimulus Macrophage Attacking E.coli (SEM x8,800) nullAdaptive ImmunityCharacteristics of Innate and Adaptive ImmunityCharacteristics of Innate and Adaptive ImmunityNo Immunologic memory Antigen independentNo time lagNot antigen specificAntigen dependentA lag periodAntigen specificDevelopment of memorynull Type of infection Type of immunity Extracellular bacteria Antibody-mediated Neutrophiles; Complement Exotoxins Antitoxins; SIgA Intracellular bacteria cell-mediated immunity null*Hospital infection (nosocomial infection)null*Conception: Nosocomial infection are those that arise during hospitalization as a comlication of another illness. e.g. acquired in hospital. 1. Classification According to the sources of pathogens: ①Endogenous nosocomial infection (self-infection). Conolization changed; lower immune function; dysbacteriosis. null*② Exogenous nosocomial infectio (cross-infection) patients; carrier; environment; animal. according to the infection position urinary drainage infections most common. Surgical infections; Skin infection; null*2. Common proterties of pathogenic microbs Conditional pathogen. Drug-resistant bacterium. New pathogen. Higher resistance to environments.null*null*null*null*3. prevention and control Asepsis: sterilization and disinfection. operation room; hand wshing; person 2. Isolation precation: patients; drainage-secretion; blood mainpulation.null*3. Antibiotics application inrationality 4. Organization: surveillance network. main principles: prevent disease; reduce the costs of medical care.