医学微生物学英文版教学课件：第5章 Bacterial Infection and Immunity

1、Chapter 5 Bacterial Infection and Immunity2 Section 1 Normal flora and Opportunistic pathogen 3normal flora the microorganism that parasitize on the body surface or tracts connecting with external, dont harm the host in ordinary condition.4I.Distribution of normal flora skin oral cavity: anaerobes i

2、ntestinal tract: anaerobes: aerobes=1000:1 vagina: Lactobacillus. respiratory 56II. Role of normal flora 1. biological barrier: antagonism 2.nutrient synthesize : amino acid, VB, Vk 3.immunity: enhance and develop and maturation of immune system 4. anti-aging 7Opportunistic pathogen some bacteria ar

3、e unable to cause infection in ordinary condition , but can initiate infection under some certain condition.Normal floraOpportunistic pathogencondition8opportunistic pathogen If: (1) host immunity reduce (2) translocation normal flora leave their ordinary habitant and gain access to other part (3) d

4、ysbacteriosis widely use antibiotics, sensitive bacteria were killed, the resistant bacteria reproduce rapidly balance of normal flora was broken 9Section 2 Bacterial Pathogenesis Mechanism10virulence: refers to extent of pathogenicity. median lethal dose(LD50): The number of pathogens required to c

5、ause lethal disease in half of the exposed hosts is called an LD50. median infective dose(ID50 ): The number of pathogens required to cause disease (or, at least, infection) in half of the exposed hosts is called the ID50.11Infection and disease Virulence the amount of invading bacteria the portal o

6、f entry the immunity of host 12Virulence Surface structureInvasive substanceexotoxinendotoxinInvasivenesstoxin13(I)Invasiveness： The ability of bacterium to resist host defence, colonize, multiply and spread. 14 1. adherence factors -surface structure bacteria to host cell: adhesin:pili capsule: fla

7、gella bacteria to bacteria: microcolony biofilm:15common pili16图为定植于静脉导管表面的表皮葡萄球菌生物膜扫描电镜照片（6000）。（From Lansing M. Prescott et al. Microbiology, 5th Edition, McGraw-Hill Companies; 2002: p92017 荚膜capsule182.Penetration and spread invasin invasive enzyme - exoenzyme coagulase- S. aureus fibrinogenfibr

8、in surround bacteria hyaluronidase (spreading factor) hydrolyze hyaluronic acid tissue loose B. spreads streptokinase. SK -Lyse fibrin B. spreads 19(II). toxin 1.exotoxin：excreted by living cells, G+ bacteria polypeptide Heat-unstable, 60C, 1-2hr destroyStrong antigenicity，exotoxin toxoidhighly toxi

9、chigh selection for tissues structure : A subunit-B subunitneurotoxin cytotoxin enterotoxin 20exotoxin subunit A：toxicity active subunit B: non-toxicity , bind receptor of sensitive cell21 exotoxin neurotoxin： tetanospasmin spinal cord tetanospasmin (neurotoxin) along nerve fibers (retrograde) anter

10、ior horn cells of spinal cord, attaches to cell membrane of CNS; enters cell and exerts biological activity of toxin causes convulsive contraction of muscle cytotoxin: diphtherotoxin inhibit cell protein synthesis enterotoxin: cholera toxin 2223A severe case of tetanus. muscles, back and legs are ri

11、gid muscle spasms can break bones can be fatal (e.g respiratory falure)24Clostridium tetani25This child has diphtheria resulting in a thick gray coating over back of throat. This coating can eventually expand down through airway and, if not treated, the child could die from suffocation26Corynebacter

12、ium Diphtheria27282. endotoxin integral part of G bacteria cell wall. release after bacteria disintegration LPS, main toxic part: Lipid A heat-stable: 160 2-4hr cant converted into toxoid weakly toxic non-specificity all endotoxins produce the same symptoms. fever WBC reaction endotoxemia and shock

13、Shwartzman and DIC29内毒素结构示意图30 Section 3 Anti-infectious Immunity 31 Non-specific or innate immunity barrier structures Secretory molecules PhagocytesNK cells32 1. Skin and mucosa barrier the intact skin and mucous membranes of the body afford a high degree of protection against pathogens. secrete b

14、actericin: fatty acid, lactic acid，antibacterial peptide, lysozyme，lactoferrin etc. normal flora2.hemo-Spinal Fluid barrier 3. placental barrier Anatomical barriers33Phagocytic cells Small phagocytic cell - neutrophils larger phagocytic cell - MPS mononuclear phagocyte system 34 1. The steps of phag

15、ocytosis : chemotaxisrecognition and bindingingestiondigestion(phagolysome)(phagosome)35362. microbcidal mechanism：phagosomelysosomephagolysomefusedigestion of the ingested material 373. Results of Phagocytosis complete phagocytose： The lysosomes fuse with the phagosomes containing the ingested micr

16、obes and the microbes are destroyed. 38 un-complete phagocytose: Some bacteria, such as Mycobacterium species , are more resistant to phagocytic destruction once engulfed. tissue damage： hydrolase inflammation394041Secretory molecules 1complement 2lysozyme 3defensin 4. interferonNatural Killer Cell4

17、2Acquired immunity humoral immunity cell-mediated immunity IgGIgDIgMIgEIgACD+4Th1CD + 8CTLperforingranzyme IFN-IL-2、TNF- Mucosa immunitySIgA43 I. Anti- extracellular bacteria 1. Phagocytic cells: neutrophils and macrophages 2. Antibody and complement: - important factor The main function of antibodi

18、es are neutralize bacterial toxins (IgG), opsonize bacteria(IgG), activate complement( IgG, IgM) interferes with attachment to mucosal surfaces (sIgA). 3. Cell mediated immune response: CD4 T cell44 II. Anti-intracellular bacteria1. Phagocytic cells: 2. Cell mediated immune response: -important fact

19、or: the main function of cell mediated immunity (CD4,CD8 T cell) are to protect against intracellular bacteria. 3. Mucosa immunity: sIgA is important in local (mucosal) immunity.45 facultative intracelllular bacteria mycobacterium tuberculosis salmonella typhi brucella legionella pneumophla obligate

20、 intracelllular bacteria rickettsia, chlamydia46Occurrence and development of bacterial infection Secction 447Origin of infection 1.Exogenous infection (1) patient (2) carrier (3) animal 2.Endogenous infection normal flora48 The route of infection 1. respiratory tract 2. digestive tract 3.damaged sk

21、in or mucous membranes 4. blood 5.arthropod vector 6. contact: sex contact (STD)49The type and outcome of infection 50. inapparent infection. apparent infection. carrier state51apparent infection acute infection local infection chronic infection systemic infection furuncle carbuncle bacteremia toxemia septicemia pyemia52 whole body infection toxemia: is the presence of exotoxin in the blood.endotoxemia: is the presence of endotoxin in the blood.bacteremia: is an invasion of the bloodstream by bacteria.septicemia: illness that occurs when poisonous substances (toxins) produced by certain