M5 b.xlsx by cuiliqing


									                                                                                                               Module 5

                                                        chemical substance having capacity to inhibit (bacteriostatic)
                                                        or kill (bactericidal) bacteria

                                                        soluble; selective toxicity; not easily altered; non-allergenic;
properties of effective
                                                        stable (degraded/passed slowly); resistance not easily acquired;
                                                        low cost
                                                        drug treatment prior to a procedure/operation; prevents
                                                        endocarditis (heart valve infection); also for patients with
antimicrobial prophylaxis
                                                        facial/skull fractures, immunocompromise, recently received
                                                        jaw radiotherapy, or having prosthetis, shunts, or bone grafts
antibiotics classes
                                                      B-lactam, cephalosporins, cycloserine, bacitracin, vancromycin;
cell wall inhibitors                peptidoglycan     common use against gram+ since gram- has outer membrane
                                                      acting as barrier
                                                      polymyxin B & polymyxin E are the only antibiotics for
membrane disruptors                                   membrane disruption; act as cationic detergents; high toxicity
                               (gram- outer membrane)
                                                      thus restricted to external infections (gram-)
                                                        aminoglycosides (striptomycin, amikacin, gentamicin) often
                                                        used synergistically with another antibiotic; tetracyclines
                                    30S inhibitors      (tetracycline, doxycycline, demeclocycline) are "bone seeking" -
                                                        not used in children (impair bone development & stain teeth) &
protein synthesis inhibitors                            can cause photosensitivity in some patients
                                                        chlrramphenicol - limited used since it can disrupt bone
                                                        marrow cells's mitochondria and cause aplastic anemia;
                                    50S inhibitors
                                                        macrolides (erythromycin, clrithromycin, azithromycin) -
                                                        commonly used for numerous infections

                                                                                                                Module 5

                                                      Normal Flora
                                                         tooth surface - Streptococcus mutans
                           due to specificity of ligands small intestine epithelium - E.coli
tissue preference
                           to colonize specific          nasal membrane - S.aureus
                           receptors                     skin - S.epidermis
                                                         throat - Coryenbacterium diphtheriae
                                                       1) prevent colonization by pathogens by competing for resource
                                                       2) synthesize vitamins (excretion - in excess of their needs)
benefits of normal flora                               3) antagonize non-indigenous species (chemical warfare)
                                                       4) stimulate development of some GI tract tissues
                                                       5) help hose immune system (induce cross-reactive antibodies)

Gram-positive microbes
Gram-negative microbes


        dry skin

       moist skin

 transient pathogens of


                                  upper (URT)
    respiratory tract
                                  lower (LRT)
       oral cavity
                                  body fluids
  normally stirile areas            tissues
                               upper urinary tract     kidneys and bladder

                                                        normal flora
                                                                                                                     Module 5

                                                         1. Host immune system tries to limit microbial infection
disease process            host-parasite interactions    2. Microbe tries to neutralize host defenses
                                                         3. Signs & symptoms are the results of immune response
                                                         Enzyme mediation; Adherence; Toxigenicity, Resistance to
virulence mechanisms              E.A.T.R.I.C.E.         antibiotics, Invasion & growth, Circulating/spreading , Evasion of
                                                         immune system
identifying microbe that                                 many normal flora can become opportunistic pathogens;
                                many challenges
causes disease                                           silent/subclinical infections (e.g. Thyphoid Mary)
                                                         1. Observe presence of microbe with disease
                                                         2. Isolate & culture microbe on artificial media
  Koch's Postulates of                                   3. Infect another host with isolated/cultured microbe
         1884                                            4. Same microbe is re-isolated from new host blood/lesion
                                                         cause-and-effect not always fulfilled; some microbes cannot be
                                  Incumbrances           cultured; cannot address polymicrobial causation; some agents cause
                                                         diseases by exotoxins (e.g. foodborne)
                                                         1. Nucleic sequence is associated with disease
                                    Summary              2. Nucleic sequence is absent in healthy host
   Molecular Method                                      3. Nucleic sequence is absent with resolution of disease
                                                         hybridization & amplicfication of polymerase chain reaction (PCR)
                                                         method (conceived by Kary Mullis in 1983) offer sensitivity &
                                  microbial ID
                                                         specificity w/o cultivating organisms
Virulence Factors & Mechanisms
                                                         Shigella dysenteriae, Salmonella typhi, Vibrio cholerae,
                               Ingestion (GI tract)
                                                         Campylobacter jejuni, Poliobirus (sewer organism)
                                                         Staphylococcus aureus, Clostridium tetani, Rickettsia rickettsii,
                               Injury/trauma (skin)
     Transmissibility                                    Rickettsia typhi
   (virulence factor 1)                                  Strptococcus pneumoniae, Neisseria meningitides, Haemophilus
                           inhalation (repiratory tract)
                                                         influenzae, Mycobacterium tuberculosis, rhinovirus
                               STD & transplacental      Neisseria gonorrhoeae, Treponema pallidum, Chlamydia
                              (reproductive organs)      trachomatis, HIV
                            adhesin / fimbrial adhesin bind to glycoproteins of host
                                                         lipoteichoic acid as adhesins found on fimbriae of Streptococcus
                             fimbriae (common pili)
        Adherence                                        salivarius (Board question)
   (virulence factor 2)             glycocalyx           capsule/slime layer can adhere (e.g. Streptococcus mutans )
                                                         glucosyltransferase catalyzes formation of extracellular glucans
                                                         (involved in dental plaque & trapping of lactic acid produced by
                                  (slime layer)
                                                         Streptococcus mutans ) from sucrose --> carries
                                                         Samonella - invasion of epithelium;
  Invasion into tissue
                                                         Shigella dysenteriae - GI (resists lysosomes, bile, & low pH);
       & growth                  Some specificity
                                                         many have tropism toward particular cell type (e.g. Yersinia,
  (virulence factor 3)
                                                         Neisseria gonorrhoeae, Chlamydia trachomatis, Shigella )

                                                                                                                Module 5

                                                   attacks host cell membrane, lyses cell (hemolysins lyse RBCs and
                           membrane active toxins
                                                   phagocytes); e.g. Pseudomonas aeruginosa (elastase)
                                                   secreted by many gram- & gram+; bind to host cell receptor, toxic to
                                                   cell; e.g. Clostridium difficile exotoxin B
                                                   B adheres to host cell receptor; A (enzymatic component transported
                                 A-B toxins        by B) attacks host cell once inside; e.g.
                                (exotoxins)        diphtheria toxin (inhibits protein synthesis), pertussis toxing (raises
                                                   cAMP activity), Verotoxin from E.coli O157:H7 (causes bloody
                                                   diarrhea), anthrax toxin
       Toxigenicity                                tetanus toxin blocks release of inhibitory neurotransmitter glycine to
   (virulence factor 4)        neurotoxins         cause spasms; botulinum toxin blocks release of acetylcholine to
                                (exotoxins)        cause placcid pralysis; diphtheria inactivates elongation factor to
                                                   impede protein synthesis
                               enterotoxins        exotoxins linked to GI signs/symptoms (E.coli, S.aureus, Bacillus
                                (exotoxins)        cereus, Clostridium difficile )
                              superantigens        cause exaggerated immune response (toxic shock); e.g. Staph
                                (exotoxins)        poisoning enterotoxin, S.aureus TSST-1; S.pyrogenes
                                                   Lipid A (toxic moiety of LPS in gram-negative bacteria) can cause
                                 endotoxin         fever, hypotension, shock, & DIC (dissiminated intravascular
                                                   act locally to damage host cells; facilitate spread & growth of
                           invasins or spreading
                                                   pathogen; e.g. staph coagulase promotes the development of
                                                   protective fibrin clot to avoid phagocytosis
Enzyme-mediation tissue                            Legionella & Mycobacterium inhibit fusion of phagosome with
                        unique enzymatic virulence lysosome to avoid host degradative enzymes;
                                  factors          Yersinia hijacks, paralyzes, disarms, & enslaves macrophage to
                                                   prevent phagocytic oxidative bursts & inhibit release of pro-
                                                   inflammatory cytokines
                                                   deters phagocytosis; e.g. Neisseria meningitidis , Streptococcus
                         Encapsulation (capsule)
                                                   pneumonia , & Haemophilus influenzae
   Evasion of immune                               a cell wall protein of group A strep fimbria with antiphagocytic
                                 M protein
          system                                   properties
                                                   a cell wall protein in S.aureus ; binds to IgG to inactivate antibody &
                                 protein A
                                                   prevent activation of complement
                              "escape artist"      some escape phagosome to multiply in cytoplasm (Listeria )

                                                                                                                    Module 5

                                            Virus = "poison" in latin
Structures & characteristics
basic structures of virus      nuclic acids + proteins & typically a lipid-containing envelope
                               reproduce in host living cells only; no trace of independent metabolism;
characteristics of virus
                               reproduced/created in assembly fashion
capsomeres                     small protein subunits composed of several small proteins; combined to form the caspid
                               protein covering/surrounding core of nucleic acid & (sometimes) enzymes:
caspid (nucleocaspid)          - extended nucleic acid form
                               - condensed nucleic acid form
virion                         the complete infectious virus particle
                               membrane-like covering of some viruses; combination of host membrane & some virus
spikes (peplomeres)            proteins embedded in envelope & project from surgace; usually have enzymatic activities
nucleic acid                   DNA or RNA; typically not both with any substantial amount
viremia                        condition in which viruses enter the blood stream
lytic infection                lysolytic cylce
                               can be:
                               1) latent/hidden infection: intermittent acute episodes of virus productions between which
                               there may be absence of virus particles, or
persistent infection           2) chronic infection: nonlytic production of viru, continue presence of virus without
                               presence of disease (Hepititis B virus)
                               3) transforming: host cells are immortalized and properties altered to those of cancer cells
                               (HPV and cervical cancer)
inclusion body formation
cytopathic effects (CPE)
plaque formation
pock formation                 in embryonated eggs
Control of viral infection     1) avoidance; 2) quaranting; 3) vaccines; 4) passive immunity; 5) antiviral agents

                                                                                                                  Module 5

                                        Bacterial Growth & Culture
bacterial growth
                                                         E.coli ~20 mins
binary fission           1 - 2 - 4 - 8 - 16 - 32 …
                                                         M.tubercolosis ~24 hrs
                                                         optical density (dead & live); colony-forming units (CFU, viable
bacterial count
                                                         cells); biomass (washed, dried, weighed - dead & live)
                                                   Lag (biosynthesis); log (exponential growth); stationary (zero
bacterial growth curve              4 phases       growth); decline/death (exponential decline, determined only
                                                   by CFU method)
                                                   defined (known); complex (no formula); enriched (+GFs for
                               liquid (broth) or
growth media                                       fastidious/picky); selective (e.g. antibiotics); differential
                                semi-solid (gel)
growth requirements      WENCpH (water, energy, nutrients, carbon, pH/O2/CO2/temp)
                                photosynthesis     photon energy; generally not medically important
                                                   anaerobic substrate-level phosphorylation; no ETC; lactic,
energy (metabolism)              fermentation
                                                   butyric, propionic, mixed acids
                                  respiration      aerobic; anaerobic (not synonymous to fermentation)
carbon source                 "sugar"; some CO2    most bacteria use glucose (or equivalent)
environmental factors        T, pH, O2, H2O/osm    obligate (w/o alternative); facultative (has options)
                                  cold < 20 C      obligage psychrophiles/cryophiles
                            relatively cold 0-35 C facultative psychrophiles/psychrotrophs
                              moderate 12-42 C     mesophiles - most pathogenic bacteria are mesophiles
                            hot > 50 C and > 80 C  thermophiles and hyperthermophiles
                                    low pH         acidophiles
pH                                neutral pH       neutrophiles - most pathogens are neutrophiles
                                    high pH        alkaliphiles
                         obligate aerobe           O2 mandatory; has enzymes for ROS
                         microaerophile            O2 required at lower level; has enzymes for ROS
oxygen                   facultative anaerobe      O2 used if available; has enzymes for ROS
                         aerotolerent anaerobe     O2 tolerated but not used; most has enzymes for ROS
                         obligate anaerobe         O2 is toxic; no enzymes for ROS
carbon dioxide (CO2)     capnophiles               require high CO2 (3-5%); special culture conditions
                         halophiles                need high salt concentration
                         osmophiles                need high osmolarity/sugar solution
                                     BSL-1         not known to cause disease in healthy adults
                                     BSL-2         associated with humans; transmittable by contact
biosafety levels
                                     BSL-3         serious or fatal disease w/ potential aerosol exposure
                                     BLS-4         toxic agents; life-threatening; aerosol transmission

                                                     bacterial growth
                                                            Module 5

                        Taxonomy, Morphology, & Structure
shapes & arrangements

                                bacterial morphology
                                                                                                                    Module 5
                             causative agent directly transmitted from 1 person to another (TB, chicken pox); botulism is
contagious or communicable
                             not a communicable disease since we ingest preformed enterotoxin
Pathogenesis                 morbid process development (by host)
pathogen                     causative agent (virus or microbe)
pathogenicity                producing morbidity or disease (refers to microbe)
endenmic                     present at low level in the community (always present)
epidemic                     occurrence higher than usual (regional)
pandemic                     worldwide distribution (global, e.g. H1N1)
                             microbial attributes contributing to disease process (linked to capacity to produce disease);
virulence factors            e.g. invasiveness, evasiveness, toxigenicity; do not include housekeeping functions (e.g.
                             microbial invasion, colonization, & growth (may not mean disease); manupulating host
                             physiology (cough, sneeze, diarrhea) are sensible strategies of microbes
                             deivation from normal structure or interruption of normal function of body; can occur w/o
                             presence of microbes (enterotoxins)
enterotoxin                  protein toxin released by microbes; ingestion of it causes disease/adverse effect
endotoxin                    structural components of microbe released when it is lysed; e.g. lipid A of LPS
exotoxin                     toxin secreted by microbe (while it is alive in host)
                             the number of microbes required to produce disease
infectious dose              (Shigella - only need a few; Samonella - take a very high number of microbes)
                             ID50 = dose required to produce infection in 50% of hosts
                             subjective evidence (not measured); constitutional symptoms are symptoms that can affect
                             many systems of the body, such as: fatigue, malaise, delirium, nausea, & vomitting
sign                         objective indicator of disease: elevated blood pressure, fever, icterus/jaundice
                             killing, inhibiting, or removing of microbes that may cause disease; typically chemical on
                             inanimate object; disingection is NOT equivalent to stirilization
antisepsis                   chemical control of microbes on living tissues (persons)
alcohol                      70% solution used for skin antisepsis
aldehydes                    inactivate proteins - sporicical and able to act as sterilizing agents
halogens                     halides or halide-releasing agents; corrosive (oxidizing agents)
phenolics                    effective in presence of organic matter; irritating and associated with odor (lysol)
quaternary ammonium
compouds                     cationic detergents that solubilize membranes and denature proteins
                             antiseptics and plaque-controlling agents (e.g mouthwash); cation membrane permeability
                             perturbing agents

sabouraud's dextrose agar    used in cuture of fungi
germ-tube test               used for Candida albicans and Candida dubliniensis (yeasts)
Methenamine silver stain     stains fungal walls black on a pale green background
electron dense stains        used for electron microscopy
PCR molecular method
phage -typing                based on differences in susceptibility to bacteriophages
genetic typing w/ RFLP       restriction fragment length polymorphism (RFLP) "fingerprinting"


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