* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download I. Microbes
Survey
Document related concepts
Triclocarban wikipedia , lookup
Horizontal gene transfer wikipedia , lookup
Molecular mimicry wikipedia , lookup
Human microbiota wikipedia , lookup
Neonatal infection wikipedia , lookup
Infection control wikipedia , lookup
Plant virus wikipedia , lookup
Introduction to viruses wikipedia , lookup
Hospital-acquired infection wikipedia , lookup
Human cytomegalovirus wikipedia , lookup
Marine microorganism wikipedia , lookup
Virus quantification wikipedia , lookup
Henipavirus wikipedia , lookup
History of virology wikipedia , lookup
Bacterial morphological plasticity wikipedia , lookup
Bacterial cell structure wikipedia , lookup
Transcript
Medical Chapter 1 Microbiology Introduction I. Microbes 1. Definition (microorganism): are the little and simple organisms with rapid growth rates. 2. Classification: 1) Non—cellular type Such as: viruses General Characteristics of Viruses : 1. Smallest: 20 – 300 nm, most were too small to be seen with the light microscope , filtrable. 2. Simplest: non-cellular entity, contain DNA or RNA and protein. 3. Obligate intracellular parasites (专性细胞内寄生): growing only within the living cells. 4. Self-replication (自我复制): Once it has invaded a cell it is able to direct the host cell machinery to synthesize new intact infectious virus particles (virions). Definition of a virus: 2) Prokaryotic type No nuclear membrane or mitotic apparatus, only nuclear region can be seen, which composed of DNA. No separate internal membrane bound organelles . Such as: Archaebacterium(古细菌): Eubacterium(真细菌): Bacterium Mycoplusma Chlamydia Riclcettsia Spirochetes Actinomycetes Cynaobacterium(蓝细菌):no pathogenesis to human 3) Eukaryotic type intracellular membrane —enclosed organelles, nucleus : two membrane layers Endoplasmic Reticulum (ER): rough ER ;Smooth ER Mitochondria Such as Fungi : hyphae and yeast 3. Distribution of Microorganisms: 1) In environments. 2) In human organisms II Microbiology and Virology 1. research objective : Pathogenic Microbes 1)biological properties 2)pathogenesis and immune response 3) Diagnosis 4)therapy and protection Microbiology: Virology:is the study of viruses, complexes of nucleic acids and proteins that have the capacity for replication in animal, plant and bacterial cells. 2. History Leeuwenhock: invent Microscope in 1674 . Pasteur : pasteurization , Vaccine Koch : solid medium, purify bacteria Pathogenic microbe criterion Lister : disinfection aseptic technique Iwanovsky : virus. 3. Modern Microbiology 1) Most bacteria were controled by antibiotics. Drug-resistant strains—> resistence plasmid. 2) Normal flora—opportunistic pathogens (flora disequilibrium super-infection ) Hospital acquired infections. New bacteria : Helicobacter pylori—chronic gastritis. 3) Viral researches have made progress. New presented viruses: AIDS New diagnostic techniques . ELISA; PCR( polymerase chain reaction.) Viral infection associated with tumors: mechanisms of Viral disease; anti-infection immunology and develop vaccines: Research tools of molecular biology: anti-virus drugs: 4) New type vaccine . Microbial genomic program, MGP . Basic Principles of Microbiology Chapter 2 Basic Properties of microbes Section I Bacteria I . Size and Shape of bacteria (I ) Size of bacteria Measure unit: um(micrometer): Coccus 1 um (II) Shape of bacteria 1. coccus (cocci) 1) diplococcus : in pairs 2) streptococcus: long chain 3) tetrad and sarcina: bacillus 2—3um 4) staphylococcus: irregular cluster 2. bacillus (bacilli): rod 3. Spirilla bacterium 1)vihrio v. cholera 2)Spirillum Helicobacter H. pylori II. Basic Bacterial Structure cell wall Basic structure cell membrane, mesosome Cytoplasm: ribosome, plasmid, cytoplasmic granules; nucletid (I)cell wall 1. function : 1)protection 2) keep the constant shape . 3)antigenicity . 4) exchange material 2. structure and chemical composition: peptidoglycan(mucopeptide) 1)polysaccharide backbone: N-acetyl glucosamine link N-acetyl muramic acid with 1.4 –glucosidic bond 2)tetrapeptide side chain: link muramic acid. ala glu lys ala 3)pentaptide bridge: G+ : L—glycine; G- : diaminopimelic acid 3. Special components of Gram-positive cell wall (1) eichoic acids : wall teichoic acid and membrane teichoic acid functions : 1) bind Mg2+(magnesium) upply of this ion to the cell 2) provide the cell with its consistency 3) adhesion ------pathogenicity 4) antigenicity (2) polysaccharides may contain a variety of sugars. 4. Special components of Gram-Negative cell wall . (1) peptidoglycan (2) Outer membrane : exchange receptor(sex pili phaqe) 1) Lipoprotein are firmly but non covalently attached to the peptido-glycan and out membrane 2) lipopolysaccharide, LPS a complex and unique glycolipid consisting of three distinct but covalently linked regions: a) lipid A: glucosamine disaccharide units connected by pyrophosphate bridge . endotoxin , non-genus specific b) core polysaccharide c) specific polysaccharide “O” Ag (II)Cell membrane mesosome : invaginated vesicular membrane,to increase membrane area such as chondriosome(线粒体) and spindle. Function as 1) spindle-like(类纺锤体):cell division 2) chondroid(类线粒体): (III)Cytoplasm plasmid : extra-chromosomal genetic material, circle double streands DNA, to replicate independently, to carry genetic information, to control a wide rang of functions to bacteria. (Fertility)factor F ---------control sex pili factor R----------control drug resistance col factor ------control E col: to produce bacteriocin. III. Special structure of bacteria Specific structure: capsule, flagellum, pillus, endospore (I)capsule 1. Concept: bacteria secrete a slime layer outside the cell wall, which is composed of polysacchride or polypeptid. Such as :pneumococcus, anthracis >0.2um capsule <0.2um microcapsule slime layer Washed off does not appear to be associated with the cell. 2. Functions: condition , enviroment host body 1. anti—phagocytosis surface phagocytosis .opsonic phagocytosis 2. anti-dry 3. adherence (粘附作用) (II)flagella 1. Concept: long filamentous appendage. Originate: in the protoplasmic membrane, 2. Functions: 1). motility 2). antigenicity “H”-Ag , some bacterin 3). pathogenicity and adherence: (III)pili (pilus) 1. Concept: filamentous appendage on the surface of bacteria, shorter straighter, and thinner than flagella. 2. Classification 1). common pili 100—200/cell adherence organ of bacteria, adhere to the surface of mucosal membrance ,be associated with pathogenicity. 2) sex pili 1—4/cell, male bacteria with sex pili, to transfer of genetic material (DNA)during bacteria conjugation F+———F- (IV) spore 1. Concept: round or elliptic minute (微小的) body formed inside the bacteria —endospore dormant form (resting forms):spore vegetative form : bacteria 2. Functions: highly resistant to heat . chemical .dry. reasons: (1)many layers .thick coat (2)little water. 40% free water (3)large amount of calcium dipicolinate (4)heat-stable enzyme (DPA,吡啶二羧酸钙) destroy spore: autoclave, under 121°C 1.05kg/cm2 for 15—30′ 3. forming: inadequate nutrition IV Special living form of bacteria. Bacterial L—Forms: cell wall deficient form Some bacteria's form of small filterable protoplasmic elements with defective or absent cell walls. 1) Morphology: spherical body, pleomorphic and plastic. Colonies: fried egg 2) Media . high osmotic , reversion 3) Pathogenicity: Similar to the infection of virus or mycoplasma (organisms without wall) Infiltration of mononuclear cells and lymphocytes and different from that of the bacterial infections , with mainly infiltration of neutrophils. V Bacterial metabolism Metabolic products 1. Catabolic products and biochemical reaction Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances,which can be used as mark to identify the class of the bacteria. 2. Anabolic products and clinical significance 1) pyrogen polysaccharide of G- cell wall(LPS) that cause a rise in temperature in an animal or human body is called pyrogen . anti-high temperature 121°C, 30’. Cause fluid infusion reaction, 2) toxin and invasive enzymes exotoxin endotoxin enzyme 3) pigment water—soluble P. aerogenosa ---green fat ---soluble S. aureus —golden 4) antibiotics Killing or inhibiting substances produced by some kinds of microorganisms, such as Actinomycete. 5) bacteriocin protein by certain bacteria, which can kill or inhibit the growth of related strains. VI. Bacterial multiplication 1. nutrient material (1) water (2)carbon source : energy(3)Nitrogen source constituent protein(4)inorganic ions (5)growth 2. nutrient type 1)autotrophy 2)heterotroph saprophyte; parasite 3. Bacterial growth and reproduction growth condition: (1)enough nutrients (2) Suitable PH (3) suitable temperature (4)suitable air obligate aerobe obligate anaerobe facultative anaerobe microaerophilic bacterium Reasons that obligate anaerobes can’t grow in free oxygen condition: (1) Lack of cytochrome and cytochromase----Eh 300mv/120mv (2) lack of superoxide dismutase (SOD) catalase, peroxidase.[O2-] H2O. 4. mode and spead of B. reproduction 1)Mode: binary flssion. chromosome replication . synthesize cell membrane and wall G+B chromosome bind mesosome G-B. chromosome bind membrane. 2)speed: generation time 20---30min For example: E. coli ; Myco. Tuberculosis: 18 hrs 3) growth curve: The schematic growth curve refers to a single bacterial culture, introduced into and growing in a fixed volume with a fixed (limited) amount of nutrient. a. lag phase; adaptation Bacteria are becoming "acclimated" to the new environmental conditions to which they have been introduced (pH, temperature, nutrients, etc.). There is no significant increase in numbers with time. b. logarithmic phase/ Exponential Growth Phase: most rapid reproduction The living bacteria population increases rapidly with time at an exponential growth in numbers, and the growth rate increasing with time. Conditions are optimal for growth. c. stationary phase: rate of reproduction = rate of deed With the exhaustion of nutrients and build-up of waste and secondary metabolic products, the growth rate has slowed to the point where the growth rate equals the death rate. Effectively, there is no net growth in the bacteria population. d. decline phase: the rate of dead > the rate of reproduction. The living bacteria population decreases with time, due to a lack of nutrients and toxic metabolic by-products. Section II Viruses I. Size and Shape Virion(病毒体): The basic infectious particle of a virus is known as the virion.The virion is composed of the nucleic acid genome, structural protein and in some viruses an enclosing lipid-containing envelope. Size : 20 -- 300 nm ( the most virus く 150 nm); Shape: the commonest shape ---- small spherical virus Others-----filamentous,brick,bullet II. Structure and Chemical Composition Viruses contain: a nucleic acid genome (RNA or DNA) a protective protein coat (called the capsid) A Viral envelope Non-structural protein (I) Core : Nucleic acid(核酸) 1. Single kind: consist of DNA or RNA ( never both). 1) DNA : single-stranded DNA (ssDNA): double-stranded DNA ( dsDNA ) : --- the commonest type of nucleic acid in viruses of human. 2) RNA: double-stranded RNA (dsRNA) : single-stranded RNA (ssRNA): --- the commonest type of nucleic acid in viruses of human.. +ssRNA : is the same as the viral mRNA ,can direct as viral mRNA -ssRNA: as a template transcribe complementary mRNA. Retrovirus: +ssRNA 2. Functions: 1) virus replication: template 2) genome (基因组): encodes genetic information. 3) infectious nucleic acid(感染性核酸): refer to some viral nucleic acid which can enter cells and reproduce new viruses,such as dsDNA V and +ssRNA V. *segment of RNA (分节段 RNA) *open reading frame, ORF(开放读码框) 3. Non-structural protein: (1) viral enzymes: such as : RNA-dependent RNA polymerase or transcriptase . (2) specific viral protein: such as : transformation protein of tumor virus. (II) . Capsid (衣壳): protein coat , 1. capsid is composed of distinct morphologic units---- capsomeres(壳粒) --- icosahedral symmetry: --- helical symmetry: --- complex symmetry: 2. Functions: 1) protection (protect viral nucleic acid from enzymic action). 2) specific binding sites. 3) antigenicity of capsid protein. (III). Envelope (包膜): lipid, glycoprotein 1. Consists of lipid bilayer and glycoprotein: lipid --- derived from host cell membrane. Glycoprotein--- coded by the viral genome. Spikes(刺突) --- virus-encoded glycoprotein protruding from lipid bilayer, which are important for adsorption and entry into the host cell. 2. Functions: 1) as the binding sites(for enveloped virus). 2) antigenicity of glycoprotein. III. Viral Multiplication Replication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle. (I.) Replication cycle(复制周期): 1. adsorption (吸附): interaction between specific binding sites on viral capsid (or envelope) and specific receptors on host cell surface. 2. penetration(穿入):virus enter the cells. Entry of Naked viruses: endocytosis Entry of enveloped virus : (1) simple fusion of membranes --expels nucleocapsid into cytoplasm (2) entire particle taken up by endocytosis-- virus still in vesicle which fuses with endosome (due to low pH) 3. uncoating(脱壳): Rapid change from stable structure to release of genome --depends on virus structure and presence of envelope --during which the endocytic vesicle and the viral capsid are enzymatically degraded and the viral genome is released. 4. biosynthesis(生物合成): 4.1 Three kinds of strategies for RNA viruses: (1)Positive-strand viruses a. SYNTHESIS OF VIRAL PROTEINS The mRNA is translated into a single polypeptide (polyprotein), which is cleaved. Products of cleavage include: An RNA polymerase (replicase)、Structural components of the virion、Proteases . b. RNA REPLICATION 1. Viral RNA polymerase copies plus-sense genomic RNA into complementary minus-sense RNA: 2. New minus sense strands serve as template for new plus sense strands. 3. New plus strand has three alternative fates: i. It may serve as a template for more minus strands ii. It may be packaged into progeny virions iii. It may be translated into polyprotein (In this case VPg is removed prior to translation) (2) Negative-strand viruses a. TRANSCRIPTION to refer to synthesis of mRNAs. b. TRANSLATION Messenger RNAs are translated on host ribosomes and all five viral proteins made at the same time. c. RNA REPLICATION RNA replication is the process by which new copies of genome-length RNAs are made . RNA replication occurs in the cytoplasm and is carried out by the viral RNA polymerase. The new positive strand is copied into full length minus strand. d. New negative strands may: i. be used as templates for the synthesis of more full length plus strands ii. be used as templates for the synthesis of more mRNAs iii. be packaged into virions (3).Retroviruses 4.2 DNA viruses: (1) Early gene expression:--------early phase The early transcript (primary transcript) results in the mRNAs for early proteins. The mRNAs are translated in the cytoplasm. (2) DNA replication DNA replication uses host cell DNA polymerase, which recognizes the viral origin of replication. This process of DNA replication is very similar to that which occurs in the host cell . (3) Late gene expression------late phase Late mRNAs are made after DNA replication. 5. assembly and release(装配和释放): --- by lysis of the host cell ( naked viruses). --- by budding through cell membrane (enveloped viruses). Not all released viral particles are infectious. The ratio of non-infectious to infectious particles varies with the virus and the growth conditions. (II.) Unnormal multiplication: 1. Abortive infection: When a virus infects a cell (non-permissive cell), but cannot complete the full replication cycle, i.e. a non-productive infection. 2. Defective virus(缺陷病毒): a defective virus is one that lacks one or more functional genes required for virus replication. defective virus require helper activity from another virus for some step in replication. 3. Interference(干扰现象):The infection of cell by a virus results in that cell becoming resistant to infection by other viruses. IV. UNCONVENTIONAL AGENTS Subvirus : refer to the kind of infectious factor which is smaller than virus. 1. viroid(类病毒) and virusoid(拟病毒): --To contain RNA only --They are small (less than 400 nucleotides), single stranded, circular RNAs --The RNAs are not packaged, do not appear to code for any proteins --To have only been shown to be associated with plant disease. 2. prion (朊病毒,朊粒): only protein(prion protein, PrP) cause animal and human central nervous system disease. Concepts 1. Prions - short for proteinaceous infectious particle. Prion(朊病毒,朊粒): infectious agents consisting only of protein, with no nucleic acids and ,which are responsible for a number of transmissible spongiform encephalopathy (TSEs) in animals and human. 2. PrP(朊蛋白): This protein is encoded by normal cellular gene and found in the membranes of normal cells (its precise function is not known), but can altere its conformation to distinguish the infectious agent(prion). The normal one is called PrPC(cellular PrP,细胞朊蛋白), while the infectious one is called PrPSC (scrapie prion protine,羊瘙痒病朊蛋白). Section III Medical Mycology The fungi--being eucaryotic organisms, lack chlorphyll, nonmotile, grow as single cell or as long dranched, filamentous strcture I. morphology 1. monocellular fungi: (1) yeast form; (2) yeast-like form 2. multicellular fungi: (1) hypha—A hypha is a long, branching filament that collectively form the feeding structure of a fungus called the mycelium(菌丝体). (2) spore —Spores are dispersal(散播) units of fungi. II. culture properties 1. multiplication modes: (1) Budding(芽生) 2. sabouraud medium:Dextrose, peptone, agar, pH 5.6 3. monocellular fungi---37℃; 4. grow slowly: multicellular fungi---28℃ 4 days-3 weeks yeast-form colony 6. colonal types yeast-like colony hyphomycete-form colony Chapter 3 Infection Section I Bacterial Infection Virulence refers to extent of pathogencity. Medium lethal dose, LD50: The number of pathogens required to cause lethal disease in half of the exposed hosts is called an LD50. Medium 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 I. Bacterial Pathogenesis mechanism (I) Invasiveness The ability of B .to resist host defence, colonize, multiply and spread. 1. adhesion Bacterial infections are usually initiated by adherence of the microbe to a specific epithelial surface of the host. For bacterial pathogens, successful adherence is usually a necessary prerequisite for virulence and even infection. (1) microcolony / biomembrane microcolony : bacterial microcolony formation is an event preceding mature biofilm formation. biomembrane(Biofilm): Biofilms are bacterial communities which are enclosed within a matrix of polysaccharides produced by the bacteria and adhere to a living or inert surface. In nature, biofilms constitute a protected growth modality that allows the bacteria to survive in hostile environments. (2) adhesive factor 1)pili, capsule, micro-capsule, terminal structure. 2) adhesin: colonization factor, 2. invasion ---invasion gene invasion can refer to the ability of an organism to enter a cell, although in some instances it can mean further passage into the systemic vasculature. (1) Some bacterial pathogens reside on epithelial surfaces e.g. Vibrio cholerae. (2) Other species are able to penetrate these barriers but remain locally. (3) Others pass into the bloodstream or from there onto other systemic sites. This often occurs in the intestine, urinary tract and respiratory tract, and much less commonly through the skin. 3. Penetration and spread (1) coagulase: S. aureus fibrinogen fibrin surround bacteria (2) hyaluronidase (spreading factor) hydrolyze hyaluronic acid tissue loose, B. spreads, (3) streptokinase. SK. Lyse fibrin (4) streptodornase, SD, resolve DNA. (II). toxin 1. Exotoxin Exotoxins are proteins, often enzymes, produced inside of cells and which do their damage (as with endotoxins) only upon release from the cell. (1) excreted by living cells , mainly G+ B. (2) polypeptide (3) Heat-unstable, 60°C, 1-2hr destroy (4) Strong antigenicity,exotoxin to make toxiod A toxoid is a physically or chemically inactivated exotoxin. (5) highly toxic (6) high selection for tissues a. neurotoxin:is an exotoxin that disrupts nerve cells. tetanospasmin: spinal cord b. cytotoxin : is an exotoxin that disrupts host cells. diphtherotoxin c. enterotoxin: is an exotoxin that disrupts the lining of the gastrointestinal tract. cholera toxin (7) exotoxin subunit A: toxicity subunitB: non-toxicity, bind receptor of sensitive cell 2.Endotoxin (1) integral part of G- B. Cell wall. .Liberated upon their disintegration. (2) LPS, main toxic part: Lipid A (3) Heat-stable: 160°C 2-4hr (4) Can’t converted into toxiod (5) Weakly toxic (6) Non-specific Function: all endotoxins produce the same symptoms. (1) fever (2) WBC reaction S induce neutrophi releasing factor WBC except S. typhi LPS blood platelet ,WBC,complement, kinin. Vasoactive , substances,eg, Serotonin, kallikrein. Kinins micro- circulation failure (3) Shwartzman phynominen and disseminated intravascular coagulation(DIC) (4) endotoxemia and shock II. Occurance and development of bacterial infection (I) Origin of infection 1. Exogenous infection: patient carrier 2. Endogenous infection: (II).The mode of infection resp. tract digestive tract damaged skin or mucous membranes arthropod vector contact: sex contact(STD) (III) The type and outcome of infection 1. inapparent infection 2. apparent infection 3.whole body infection toxemia: is the presence of exotoxins in the blood. pyemia: is caused by pyogenic microorganisms in the blood. endotoxemia: is the presence of endotoxins in the blood. septicemia: illness that occurs when poisonous substances (toxins) produced by certain bacteria enter the bloodstream. bacteremia: is an invasion of the bloodstream by bacteria. 4. Carrier state Section II Viral Infection and Pathogenicity I. Thepathogenesis mechanism of viral infection (I). virus – cell interactions: 1. cytocidal effect 杀细胞感染 virus which infect and replicate within cells causing the cells to lyse when the progeny virions are released. 2. steady state infection 稳定状态感染: viruses are produced from the infected cells but the cells are not killed by the process. --- integration of viral Ag in cell membranes. --- cell fusion. Such as CMV 3. inclusion body inclusion bodies:round, oval, or irregular-shaped bodies occurring in the cytoplasm and nuclei of virus-infected cells, as in disease caused by filtrable virus infection such as rabies, smallpox, herpes, etc; called also elementary b's and intranuclear inclusions. 4. cell apoptosis 细胞凋亡 Viruses have the potential to initiate or stay the onset of programmed cell death through the manipulation of a variety of key apoptotic proteins of the host cell. Such as HIV, adenovirus. ----- Cells that are induced to apoptosis: ------ shrink ------ have their mitochondria break down with the release of cytochrome c ------ develop bubble-like blebs on their surface ------ have the chromatin (DNA and protein) in their nucleus degraded ,and DNA break into small, membrane-wrapped, fragments 5. integration 整合作用 and cell transformation 细胞转化: integration: integration of the viral genome into cellular DNA . cell transformation: "the introduction of inheritable changes in a cell causing changes in the growth phenotype and immortalization". oncogenic virus --- induces cell transformation The oncogenic virus associated with human tumors: HBV--- hepatocellular carcinoma HPV --- cervical carcinoma EBV --- Burkitt lymphoma , nasopharyngeal carcinoma HSV-2 --- cervical carcinoma HTLV --- T cell leukemia II. virus – immune system interaction: 1. immunopathological reactions: 2. the injury of immune system induced by virus infection: III. The pathways of viral infections 1. horizontal transmission: (水平传播): Viruses transmission from Person -to-person: The most common STDs are listed below: Gonorrhea. Chlamydia. Syphilis. Trichomonas. Human papillomavirus (HPV). Genital herpes. Hepatitis B and Hepatitis C. Human Immunodeficiency Virus (HIV). 2 . vertical transmission(垂直传播): Viruses transmission from mother to infants or child : --- through placenta ( congenital infection, congenital deformity 先天性畸形) --- through birth canal (infection of newborn 新生儿感染) --- through Breast Milk from virus-infected mothers The viruses which can result in congenital infection : 1)rubella virus 风疹病毒 2)cytomegalovirus(CMV) 巨细胞病毒 3)herpes simplex virus-II(HSV-II)单纯疱疹病毒-II 型 4)hepatitis B virus(HBV)乙肝病毒 5)human immunodeficiency virus (HIV)人类免疫缺陷病毒 III. The type of viral infection 1. inapparent or subclinical infection viruses enter the body ,but cause no apparent clinic syndrome 2. apparent infection or infectious disease. viruses enter the body ,which can cause apparent clinic syndrome (1) acute viral infection: viruses exist in the bodies for a short time (not>6 monthes) (2). persistent viral infection: viruses exist in the bodies for a long time (>6 monthes) 1) chronic infection: virus can be continuously detected. 2) latent infection 潜伏感染: virus is usually not detectable but patient may have periodic out-breaks of disease. 3) slow virus infection 慢发病毒感染: with long incubation periods(years), subacute progressive, caused by lentivirus(HIV) , Measles virus (SSPE)or unconventional virus ( prion)。 4) delayed complication after acute viral infection. Subacute Sclerosing Panencephalitis (SSPE): is a late manifestation of measles virus infection, developing usually 6 and 12 years after natural measles infection to cause a serious viral encephalitis of children and young adults. Section III Pathogenisis of fungi 1. superficial mycoses (Dermatophytes) infect skin, nail and hair --- cause tinea *pathogenic fungi infection----exogenous infection 2.*opportunity fungi infection----endogenous infection flora disquilibrium--Candida albicans : mucocutaneous infection ---- thrush Pneumocystis carinii is an opportunistic fungal pathogen causing P. carinii pneumonia (PCP). PCP continues to be a major cause of morbidity and mortality in patients with AIDS despite the availability of prophylaxis and improved antiretroviral therapy. 3. deep mycoses----chromic granulama, tissue ulcer , necrosis Organ infection ----meningitis 4. *fungal poisoning ----Fusarium; Arthrinium; Patulin; Flavus *fungal toxin can cause cancer: aflatoxin---10g/d/personcancer 5. *hypersensitive disease penicillium; fuarium; aspergillus---asthma; urticaria; allergic rhinitis; allergic dermatitis Chapter 4. Immunity against microbe infection Section I Anti-infection Immunity I. Non-specific or innate immunity. 1. Anatomical barriers (1) Skin and mucosa Skin and mucous membranes Acid pH Fatty acids Hydrolytic enzymes (lysozyme) Proteolytic enzyems and bile 2. Phagocytic cells Phagocytosis is a process describing the engulfment and destruction of extracellularly-derived materials by phagocytic cells, such as macrophages and neutrophils. Five steps of phagocytosis are illustrated in the image below. (1) Schematic diagram of the steps in phagocytosis: a. Attachment of the bacterium to the long membrane evaginations, called pseudopodia. b. Ingestion of the bacterium forming a "phagosome," which moves toward the lysosome. c. Fusion of the lysosome and phagosome, releasing lysosomal enzymes into the phagosome. d. Digestion of the ingested material. (2) Results of Phagocytosis a. complete phaged The lysosomes fuse with the phagosomes containing the ingested microbes and the microbes are destroyed b. un-completed phaged Some bacteria, such as Legionella pneumophilia (inf) and Mycobacterium species (inf), are more resistant to phagocytic destruction once engulfed. 3. NK cells Role in early viral infection or tumorogenesis before activation of acquired immunity. 4. Secretory molecules Complement system – 20 proteins in a controlled enzymatic cascade which targets the membrane of pathogenic organisms and targets theme for destruction Interferons – proteins made by cells in response to virus infection that induced a generalized antiviral state in surrounding cells II. Specific or adaptive immunity. 1. humora immunity 2. cell-mediated immunity Section II Immunity against bacteria I. anti- extracellular bacteria 1. Phagocytic cells: Neutrophils (PMN) and macrophages and monocytes are the most important cellular components of the non-specific immune system. 2. antibody and complement 3. cell mediated immune response II. anti- extracellular bacteria 1. Phagocytic cells: Neutrophils (PMN) and macrophages and monocytes are the most important cellular components of the non-specific immune system. 2. cell mediated immune response 3. mucosa immunity: IgA is the major class of Ig in secretions - tears, saliva, colostrum, mucus. Since it is found in secretions secretory IgA is important in local (mucosal) immunity. Section III Immunity against virus I . Non-specific immunity: A. Inherent Barriers Skin, Mucus, Ciliated epithelium , Low pH B. NK cell C. Humoral and cellular components (1). Interferon (IFN) (2). Complement (3). Cytokines TNF-a, IL-1 and IL-6 Interferon (IFN) 1. concept: a class of protein(glycoprotein) produced by cells in response to viral infection or other interferon inducers that protected other cells of same species from attack by a wide range of viruses. 2.classification of IFNs: Gene cell anti-viral activity Modify-immune responses IFN-α chromosome 9 blood mononuclear cell +++ ++ IFN-β chromosome 9 fibroblasts +++ ++ IFN-γ chromosome 12 Ag-activated T cell ++ +++ 3. production of IFN: (1) interferon inducers: eg. PolyI:C(poly inosinic:poly cytidylic acid), viruses and bacterial endotoxins, etc (2) Mechanism : IFN inducer acts on cell receptors --- IFN gene activation--- transcribe IFN mRNA--IFN synthesis--- IFN released 4. antiviral activity: not act directly on virus, but through induction of antiviral proteins(AVP). (1) Mechanisms: IFN combines with specific receptor on cell surface ---AVP gene actived --- AVP mRNA transcribed---AVP synthesis AVP consists of : protein kinase 2,5-A synthetase (2) Characteristics : ----not act directly on virus . ----broad-spectrum antiviral activity. ----host species specific: inhibit viral replication only in the species in which it was produced. 5. other activities: (1) anti-cancer (2) Modify immune responses ----NK activation ----macrophage activation ----Increased expression of MHC molecules II. Specific immunity 1. Humoral immunity 1) Neutrilizing antibody: blocking the virus replication from binding and gaining entry to the host cell(by the inhibition of adsorption, penetration or uncoating). (1)virolysis --- with the aid of complement----- by complement activation by antibody-coated virus particles. --- by phagocytosis -----opsonins in enhancing phagocytosis of virus particles --- by ADCC (2)Neutrilizing virion: act on free viruses , but can’t influence intracellular virus directly. 2). Non-neutrilizing antibody: hemagglutination inhibition antibodies complement fixation antibodies: 2. Cell mediated immunity: the destruction of an infected cell before progeny particles are released --- an effective way of terminating a viral infection. CTL: react with membrane-bound viral antigens and lyse the infected cells. release some lymphokines(IFN-r, TNF ). Th : release lymphokines. NK cell: lyse infected cell directly. Section III Immunity against fungi I . Non-specific immunity: A. Inherent Barriers Skin, Mucus, Ciliated epithelium, Low pH B. Phagocytic cells C. Humoral and cellular components. --- IFN, TNF-a II. Specific immunity 1. Humoral immunity----antibody 2. Cell mediated immunity: Th : release lymphokines. Chapter 5 Section I Bacterial Genetics and Variation inheritance and variation. Concept: (1) heredity(inberitance) general stability on “likeness” characteristics of progeny and parent. (2) variation . the difference between progeny and parent variation genetic substance changes .nonberitable enviroment changes I. variation examples. 1. shape and structure variation . 2. colony variation smooth colony rough colony 3. virulence variation, vaccine BCG : Bacilla of calmetter-Gueria 230 passages, 13 years. 4. Resistance variation II. Genetic substance 1. chromosome consists of a circular double strand DNA molecular, control life without introne. 2. Plasmid Extrochromosomal genetic substance. Circle double strand DNA (1) autonomous replication binding to chromosome —episome (2)contral most of auxiliary functions of bacterial cell Antibiotic resistance —R plasmid . production of fimbriae—F plasmid bacteriocin —E. coli con plasmid. in the Heritable variation bacterial (3)dispensable, it can be lost . (4)tranfer from a bacteria to another conjugative plasmid : F+ serpili nonconjugative plasmid: phage (5)Incompatibility and compatibility. Incompatibility: compatibility : bacterium can carry one or several small—a few genes .large—hundreds of genes. 3. bacteriophage. plasmid, different size : Bacteriophage Infecting bacterial virus . (1) viral common properties smallest ,simple structure , DNA/RNA, parasite in living cell (2) widespread existence (3) high host –specific parasitism I. Biological properties 1. Shape and structure Seen by EM: Tadpol , microsphere slim rod Structure: head core: DNA/RNA Capsid: protein coat Tail: pipe-like, collar, base plate, tail fib II. Interrelation between phage and bacteria 1. Virulent phage. Reproduction and lyzing Bacteria, which can replicate in cell and released in lysis of B . Replication cycle. 1) absorption and tail pins and fibers absorb teichoic receptor of B, 2) penetration : lysosome like substance lyse, injects DNA into bacteria. 3) Biosynthesis structure Phage DNA transcribe mRNA protein, enzyme phage DNA replication 4) lysis encode lysosome lysis B. release 2. lysogenic phage. infected bacterial phage doesn’t replicate it’s gene ,integrated with bacterial DNA, its replication is associated with bacterial DNA lysogenic phage (temperate phage) lysogenec bacteria prophage : The DNA of temperate phage integrated into bacterial DNA. 4.transposon: a segment of DNA that can become integrated at many different sites along a chromosome,plasmid and phage.(especially a segment of bacterial DNA that can be translocated as a whole) transposable elements insertion sequence transposon III. Mechanism of bacterial variation: 1. Mutation (1) concept: a stable heritable change of bacterial gene , spontaneous 10-6~10-9 inducing mutagen (2) type of mutation molecular foundation of mutation . Bacterial nucleotide sequence change i. base replacements transition (转换) A—G, C—T transversion(颠换)A—T C—G ii. base deletion . one base or fragment lost iii. base insertion . one base or fragment 2. genetic transfer and recombination 1) Genetic substance of B. is transferred to another bacteria. Donor bacteria : provide genetic substand Recipient bacteria : accept genetic substand 2) transformation recipient B. takes up exogenous DNA of donor B. eg : Griffith’s experiment competence : bacterial state. In which bacteria can able to take up DNA from environment in logarithmic phase 3) transduction . donor bacterial DNA is transfered to recipient bacterial by phage . (1) general transduction: any fragment of donor bacteria is transfered. (2) Specific transduction: the fragment near attachment is transfered. (3) Lysogenic conversion Bacteria acquired new properties by phage lysogenization. Eg C, diphtheria 4) conjuqation bacterial DNA is transferred from donor bacteria to recipient bacteria by F pilus. Hfr(high frequent recombinant bacterium ) (1)F plasmid F’ plasmid intergrated into chromosome. F plasmid of high freguent recombinant bacteria separated from bacteria chromosome, carrying a neighbour DNA. Sexduction. (2)R plasmid conjugative R plasmid resistance transfer factor RTF resistance factor (RF) the function of RTF is similar to F plasmid nonconjugative R plasmid. The result of gene tranfer : i. exogenous DNA was degraded ii exogenous DNA from circular ds DNA autonomous replication abortive infection iii. exogenous DNA recombine with endogenous DNA hemologeous recombination site-spcific recombination eg phage 4) lysogenic conversion 5) protoplast fusion III. Medical application 1, Bacterial indentification 2. prevention treatment of diseases. Eg . vaccine 3. screening potential carcinogen . Ames test 4. genetic engineering (1)prepare objective gene endonuclease E COR (2)objective gene recombines with vector vector: plasmid .phage . (3)recombined DNA transfer to cell .eg . E. coli (4)Screen positive cell.resistance—antibiotics. (5) Amplify objective gene and express. Section II I Viral Genetics The nature of the viral genome (RNA or DNA; segmented or nonsegmented) plays an important role in the genetics of the virus. 1. Mutations: ----permanent changes in sequence of nucleotides in nucleic acid. ----TYPES OF MUTATION: Mutants can be point mutants (one base replaced by another) or insertion/deletion mutants. ---- ORIGIN (1)Spontaneous mutations These arise naturally during viral replication: e.g. due to errors by the genome-replicating polymerase or a result of the incorporation of tautomeric(异构) forms of the bases. (2) Mutations that are induced by physical or chemical means Chemical: Agents acting directly on bases, e.g. nitrous acid Agents acting indirectly, e.g. base analogs which mispair more frequently than normal bases thus generating mutations Physical: Agents such as UV light or X-rays ---- EXAMPLES of Mutant(突变株) e.g. temperature sensitive (ts) mutants, ts 突 变 株 - These will grow at low temperature e.g. 31 degrees C but not at e.g. 39 degrees C, wt grows at 31 and 39 degrees C. It appears that the reason for this is often that the altered protein cannot maintain a functional conformation at the elevated temperature. 2. Recombination (重组)and reassortment(重配): --- Recombination (重组) :exchange of genetic material between two viruses which infected the same cell. This involves breaking of covalent bonds within the nucleic acid, exchange of genetic information, and reforming of covalent bonds. ----reassortment(重配): If a virus has a segmented genome and if two variants of that virus infect a single cell, progeny virions can result with some segments from one parent, some from the other. 3. Integration(整合): viral genome insert into host cell genome . 4. Complementation(互补作用): If we infect the same cell with both mutants, each mutant can provide the missing function of the other and therefore they can replicate. 5. Phenotypic mixing: If two different viruses infect a cell, progeny viruses may contain coat components derived from both parents and so they will have coat properties of both parents. This is called phenotypic mixing. INVOLVES NO ALTERATION IN GENETIC MATERIAL. Chapter 6 Medical Ecology and hospital infection Section I normal flora I. Concept: 1. normal flora: The microbes that parasitize on the body surface or tracts connecting with external, while don’t harm the host in ordinary condition. 2. Distribution of normal flora Mouth carity anaerobes Intestinal tract: anaerobes: aerobes =1000:1 Vagina: Lactobacillus. Skin Respiratory 3. Roles of normal flora. (1) Biological barrier: antagonism (2) nutrient synthesize : aa. VB. K. enhance absorb. (3) immue: enhance and develop and maturation of immue system acts as an antidysbacteriosis drug and as an immunostimulator. It stimulates T-cell immunity, phagocytosis, B-cell immunity. Immunostimulating effect of bioflor depends on dysbacteriosis degree and is maximal at its first stages. (4) Anti- caducity (5) Anti-tumor Secton II Flore disequilibrium (dysbacteriosis) I. Flore disequilibrium (dysbacteriosis): Balance of normal flora was broken. Flora inbalance symptom (superinfection) widely use antibiotics, sensitive bacteria were killed , the resistant bacteria reproduce rapidly. II. main reasons: 1. antibiotic therapy 2. change their normal parasite sites. they leave their ordinary habitant and gain access to other part. 3. host immunity reduce. Owing to the wide use of antibiotic, hormone and anti-concer druges. Section III opportunistic infection I . opportunistic pathogenic B some bacteria are unable to cause in ordinary condition , but can initiate infection under some certain condition. II. Characters of opportunistic pathogenic B 1. weak or no-more apparent virulence 2. drug-resistant bacteria or multiresistant bacteria 3. new opportunistic pathogenic B Section IV Hospital infection I. Concept: Hospital infection / nosocomial infection: Infections acquired during hospital stays. Incidence (annual): estimated 2 million cases annually or about 10% of American hospital patients (CDC/NNIS 1992) Incidence Rate: approx 1 in 136 or 0.74% or 2 million people in USA II. Types: Nosocomial infections by site: o Urinary tract infections o Surgical site infections o Respiratory tract infections o Blood stream infections o Skin infections o Gastrointestinal tract infections o Central nervous system infections Nosocomial fungal infections - fungi cause about 9% of nosocomial infections. o Candida o Candida albicans o Aspergillus o Fusarium Trichosporon o Malassezia Nosocomial pneumonia o Bacterial pneumonia o Legionnaires' disease o Pulmonary aspergillosis o Mycobacterium tuberculosis o Viral pneumonias o Respiratory Syncytial Virus o Influenza Nosocomial infections by pathogen: o Staphylococci o Pseudomonas o Escherichia coli Antibiotic-resistant nosocomial infections o Methicillin resistant staphylococcus aureus (MRSA) o Vancomycin-resistant staphylococcus aureus o Vancomycin-resistant enterococci (VRE) o III. Who gets Nosocomial infections? Patient Profile: Typically immunosuppressed hospital patients due to age, disease, medication, or surgery. IV. Prevention of Nosocomial infections 1.Changes to hospital staff activities: 2. Changes to the patient environment: 3. Changes to hospital environment: 4. Vaccination - use of certain vaccines may be appropriate for some patients. Chapter 7 Disinfection and sterilization Concepts: 1. disinfection : To kill pathogenic microorganisms (vegetative form) 2. sterilization : To kill all microorganisms, including .pathogenic & non-pathogenic , vegetative &spore. 3. asepsis : a state of sterility (no living bacteria) , asepsis / antiseptic technique: the technique to prevent bacteria entering human body and other matters. Aseptic technique is used in a variety of research applications, including: Animal husbandry ( immuno-compromised / barrier animals) Tissue and cell culture Diagnostics and animal healthcare procedures Survival surgical procedures 4. antisepsis: To inhibit the growth and reproduction of bacteria in vitro. 5. bacteriostasis: prevention of growth of bacteria, but without killing them. Bacteriostat: agent causing bacteriostasis. Section I. Physical methods I. heat lethal make bacterial protein denature. bacterial DNA degrade, injury cell membrane . 1. dry heat: (1) flame (2) burn (3) hot air oven: 160---170°C, 2―3hrs (4) infrared vegatatine 80---100°C 1hr spore 160°C 2hrs 2. moist heat : 1)advantages over dry heat: (1) Bacteria absorb H2O , proteinis easy to solidify and denature . (2) Strong penetration Eg. 100 th layer: dry heat 130-140°C 4hrs。72.5°C/100 th Moist heat 105°C 3hrs. 101°C/100 th (3) lalent heat gas –liquid . 2) Methods: (1) pasteurization 62°C 30′ 72°C , 30″ (2) Boiling 100°C 5′ (3) Steaming and intermittent sterilization: Arnold 3times. 2 (4) Autoclaving : 1.05 kg/ cm , 121.3°C 15-30′-spore II.radiation 1. ultraviolet light: 200---300nm interfere DNA replication ,form dimmer of Thymine . strongest spectrum 260nm, DNA absort specfurm, weak penetration : definite time and intensity stimulate skin, eyes,. Application : air . operation room 2. ionizing radiation : eg ,x-ray, r-ray. III. filtration fiter heat-labile solution eg. Serum . toxin .antibiotics. etc. seitz filter: K>EK>EK-S glassical filter: G1 G2 G3……6 thin membrane filter IV. Other: low temperature ( preserve bacteria) Section II Chemical disinfection Disinfectant: Antiseptic: 1. chemical agents and mechanism 1) heavy –metal salts (1) bind to –SH and destroy it, inhibit activity of enzymes. (2) Protein denature. Merbromin .thimerosal 0.1%disinfectant 0.01%antiseptic 2) Oxidizer H2 O 2 KMnO 4 CHCOOH(过氧乙酸) Halogen(iodine ,chlorinated lime) (1) SH S—S— enzyme (2) destroy amino group, indol group. (3) denature protein 3) surfactant combine with phospholipid increast membrane permeability bromogeramine(新洁尔灭) domiphen(杜灭芬) 4) aldehyde(醛类) farmaldehyde、 enzyme deactivity 5) alcohol 70% alcohal protein denature。 6)phenol (酚类)protein denature , destroy cell membrane。 2. Application skin: 2.5%碘酒 70%酒精 mucosa 2% 红汞 0.1%新洁尔灭 drinking water 漂白粉 patients excreta 5% phenol 2%lyson air: formalin spray 3. Affecting factors (1) concentration and time (2) properties and quantity (3) temperature and PH (4) antagonist: organs protein, excreta Chapter 8 The Examination and Treatment of Microbes Infection Section 1. The Examination of Bacterial Infection I. Detection of pathogenesis bacteria. 1. Getting a pure culture : aseptic technique + sterile media: 2. Microscopy and stains: electron microscopy. 3. isolation and identification. a. micromanipulation b. extinction dilution in liquid media c. solid media - streaking out, viable counts d. enrichment culture e. Composition of culture media, temperature of incubation, osmotic potential of media, pH etc. f. Anaerobe or aerobe? - microaerophile? II. Detection of pathogenesis bacteria antigens III. Others: 1. antibody 2. nucleic acid Section 2. The Examination of Viral Infection I. Detection of living virus: 1. animal injection(动物接种): 2. chicken embryo culture(鸡胚培养): 3. cell culture(细胞培养): primary(原代)cell culture: continuous (传代) cell culture: growth phenomenon of virus: (1) cytopathic effect (CPE)(细胞病变): --The presence of the virus often gives rise to morphological changes in the host cell. Any detectable changes in the host cell due to infection are known as a cytopathic effect. --Cytopathic effects (CPE) may consist of cell rounding, disorientation, swelling or shrinking, death, detachment from the surface, etc. (2) plaque forming units (PFU)(空斑形成单位): A plaque is produced when a virus particle infects a cell, replicates, and then kills that cell. Each plaque is the result of infection of one cell by one virus followed by replication and spreading of that virus. So we use PFU/ml to show virus’ quantity. (3) inclusion body----- round, oval, or irregular-shaped bodies occurring in the cytoplasm and nuclei of virus-infected cells, as in disease caused by filtrable virus infection such as rabies, smallpox, herpes, etc; called also elementary b's and intranuclear inclusions. II. Detection of viral antigen and antibody: ELISA, immuno-fluorescence , Western-blot III. Detection of viral nucleic acid: PCR, RT-PCR, Biochip (生物芯片) Section III The Examination of fungi Infection I. Samples: Skin scrapings suspected to contain dermatophytes or pus from a lesion can be mounted in KOH on a slide and examined directly under the microscope. II. detection and identification: 1. Direct microscopy. 2. Culture and identification (1) Sabouraud dextrose agar: (2) Culture methods: 3. Skin testing (dermal hypersensitivity) III. quick diagnosis: 1. Serology: latex agglutination may favor the detection of IgM antibodies, double immunodiffusion and complement fixation usually detect IgG antibodies. Some EIA tests are being developed to detect both IgG and IgM antibodies. 2. detection of nucleic acid: 3. Biopsy and histopathology. Gomori methenamine silver (GMS) stain. Section IV Prevention and Treatment of microbes infection I. Immunization Prevention of infection: 1. Vaccines: (1) inactivated vaccines: (2) attenuated-live vaccines: (3) *gene engineering vaccines: Fragments of the genome of the virus that the vaccine is intended to combat are inserted into protein expression vector and then transfected into bacteria, yeast or eukaryotic cell. these micro-organisms then produce enormous quantities of a protein (a recombinant protein) which will be purified and used as the basis for the vaccine. (4) *DNA vaccines: (5) *recombined viral vector vaccines: (6) synthesized(合成) vaccines: (7) subunit vaccines 2. toxoid 3. Artificial passive immunization: (1) antitoxin (2) antisera (3) PLACETAL GAMMAGLOBULIN (4) OTHERS II. Treatment of bacterial infection: 1. INHIBITORS OF CELL WALL SYNTHESIS PENICILLIN---2. Inhibitors of the functions of cell membrane 3. Inhibitors of Protein Synthesis (most bacteriostatic) (1) Antimicrobials that Bind to the 30S Ribosomal Subunit aminoglycosides irreversibly bind to the 30S ribosome and freeze the 30S initiation complex (30S-mRNA-tRNA) tetracyclines reversibly bind to the 30S ribosome and inhibit binding of aminoacyl-t-RNA to the acceptor site on the 70S ribosome. (2) Antimicrobials that Bind to the 50S Ribosomal Subunit Chloramphenicol, lincomycin, clindamycin (bacteriostatic)---These antimicrobials bind to the 50S ribosome and inhibit peptidyl transferase activity Erythromycin ---- The macrolides inhibit translocation. 4. Inhibitors of Nucleic Acid Synthesis and Function (1). Inhibitors of RNA Synthesis and Function Rifampin, rifamycin, rifampicin (bactericidal)----These antimicrobials bind to DNA-dependent RNA polymerase and inhibit initiation of RNA synthesis. (2). Inhibitors of DNA Synthesis and Function (bactericidal) Quinolones - nalidixic acid, ciprofloxacin, oxolinic acid----- These antimicrobials bind to the A subunit of DNA gyrase (topoisomerase) and prevent supercoiling of DNA, thereby inhibiting DNA synthesis. III. Treatment of viral infection: 1. antiviral agents---chemical agents: (1)Nucleoside analogues polymerase inhibitors. ACV(acyclovir),无环鸟苷――treatment of HSV through the inhibition of the viral DNA polimerase. Ara-A (Adenine arabinoside),阿糖腺苷——treatment of HSV,VZV,CMV through the inhibition of the viral DNA polimerase. AZT(Azidothymidine ) , 叠 氮 胸 苷 — — inhibit reverse transcriptase in the retroviruses, used in HIV infection Lamivudine,拉米呋定—— inhibit reverse transcriptase in the retroviruses, used in HIV and HBV infection Ribavarin,病毒唑 —— inhibit RNA and DNA polymerase, used in influenza virus infections (2)Non-Nucleoside analogues polymerase inhibitors. (3)Protease inhibitors Saquinavir. inhibitors of HIV replication. Ritonavir, Indivavir. They are the most potent inhibitors of HIV replication to date. 2. gene therapy: antisense oligonuclotide,asON 反义核酸 ribozyme 核酶 siRNA 3. immunal therapy: Ab Ck IFN Section IV TREATMENT of Fungi The primary antifungal agents are: 1. Amphotericin B. It has a greater affinity for ergosterol(麦角固醇) in the cell membranes of fungi than for the cholesterol in the host's cells; once bound to ergosterol, it causes disruption of the cell membrane and death of the fungal cell. 2. Azoles(多稀类,唑类) The general mechanism of action of the azoles is the inhibition of ergosterol synthesis. 3. Griseofulvin(灰黄霉素) Its effect depends on its accumulation in the stratum corneum where it is incorporated into the tissue and forms a barrier which stops further fungal penetration and growth. 4. 5-fluorocytosine 5-fluorocytosine (Flucytosine or 5-FC) inhibits RNA synthesis and has found its main application in cryptococcosis. Chapter 9 Antimicrobial Drug Resistance I. Principles and Definitions Drug resistance is the ability of the parasite species to survive and/or multiply despite the administration and absorption of a drug given in doses equal to or higher than those usually recommended but within the limit of tolerance. Clinical drug resistance to an antimicrobial agent occurs when the MIC of the drug for a particular strain of bacteria exceeds that which is capable of being achieved with safety in vivo. II. Resistance to an antimicrobial can arise : (1) by chromosomal mutation in the gene that determines sensitivity/resistance to the agent (2) by acquisition of extrachromosomal DNA (plasmid) carrying a resistance gene. (3) by acquisition of transposable element carrying a resistance gene. Resistance that appears after introduction of an antimicrobial agent into the environment usually results from a selective process, i.e. the agent selects for survival of those strains possessing a resistance gene. Resistance can develop in a single step or it can result from the accumulation of multiple mutations. III. Mechanisms of Resistance 1. Altered permeability of the antimicrobial agent - Altered permeability may be due to the inability of the antimicrobial agent to enter the bacterial cell or alternatively to the active export of the agent from the cell. 2. Inactivation of the antimicrobial agent - Resistance is often the result of the production of an enzyme that is capable of inactivating the antimicrobial agent. 3. Altered target site - Resistance can arise due to alteration of the target site for the antimicrobial agent. 4. Replacement of a sensitive pathway - Resistance can result from the acquisition of a new enzyme to replace the sensitive one. IV. Control of Resistance 1. correct usage of antibiotics (1) Optimising drug dosages and delivery routes Two major factors contribute to the emergence and spread of antimicrobial resistance in hospitals: a high rate of antimicrobial drug use and inadequate infection control practices. The routine reporting of susceptibility results;monitoring antimicrobial use with feedback to physicians concerning inappropriate use; (2) Selection of drugs - Use conventional drugs first in uncomplicated cases. Greater the exposure, higher will be the emergence of resistance. (3) Monitoring for resistance and early treatment of these cases to prevent their spread. 2. Clear policy of using antibiotics. Some use of antibiotics (preventive, therapeutic, growthpromoting) in food animals contributes to the pool of resistant human pathogens. Both medical and nonmedical uses of antibiotics should be reduced. 3. Studies of new antibiotics 4. get rid of the plasmid. 5. Evaluation of drug rotation strategies