Microbiology - 1st term (2013)

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jonas112
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Microbiology - 1st term (2013)
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2013-12-04 11:23:05
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Microbiology 1st term 2013
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Microbiology - 1st term (2013)
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  1. define pathogen, infection, and disease
    • pathogen: micro-org that has potential to cause disease.
    • infection: invasion and prolif. of pathogenic microorganisms 
    • Disease: infection causes damage to host tissues or function.
  2. What are fomites?
    any inanimate object that carries infection (e.g. cell phone)
  3. What is the difference b/n empiric and specific antibiotic therapy?
    empiric: given before you know what is causing the disease, usually broad spectrum

    specific: given when the sensitivity and identity of the offending organism are known. Usually narrower spectrum.
  4. Why do Abx levels testing
    • 1) therapeutic index is low: (tmt conc/toxic conc)
    • 2) if there is worry about Abx harming organ systems
    • 3) genetic hypersensitivity to drug exists
  5. What are the 4 cardinal manifestation of infection?
    • 1) fever
    • 2) leukocytosis (WBC greater than 10 or 11)
    • 3) local signs and symptoms
    • 4) systemic signs and symptoms
  6. Why would you treat fever?
    • 1) patient comfort
    • 2) harmful secondary effects
    •   -febrile conulsions
    •   -hypermetabolism
    •   -encephalopathy
    •   -hypercatabolic state
  7. why would you NOT treat fever?
    • 1) fever enhances immune activity: stumlates lymphocytes, and enhances their transformation.
    • 2) complicates interpretation of: patient's illness, response to therapy
  8. What are the three R's in specimen collection
    • The right specimen: One that should have the pathogen (e.g. CSF for neurological symptoms)
    • The Right time: while patient is still symptomatic and before Abx
    • The Right way: e.g. if sterile, KEEP it sterile from your own flora
  9. Risk factors for MRSA
    • -hospitalizations: tubes, contact, multiple Abx
    • -community: athletes, crowded, aboriginal, tattoos, IVDU
  10. VRE risk factors
    -hospitalization: tubes, multiple Abx, immunosuppression
  11. List some alpha and beta hemolytic strep
    • alpha: viridans, s. pneumoniae
    • beta: Group A - S. pyogenes, Group B - S agalactial
  12. List some common sites for anaerobic infection
    • dental infections/abscesses
    • abscesses of resp, abdo, pelvic origin
    • CNS abscesses
  13. Difference in cell wall between GNB and GPB
    • GNB walls have:
    • -less rigid walls
    • -thinner peptidoglycan layer
    • -inner and outer membrane
    • -no teichoic acid
    • -LOTS of lipopolysaccharide (lipid A is an endotoxin)
  14. What are some of the complications due to the release of LPS endotoxin in GNB?
    • fever
    • leukopenia
    • hypotension
    • DIC
    • others
  15. Answer the following about enterbacteraceae:
    1)large gram _____ rods
    2) ______ anaerobes
    3) grow in presence of _____
    4) All ferment ______+/- other carbs
    • 1) negative
    • 2) facultative
    • 3) bile acids
    • 4) glucose
  16. How does MacConkey media work?
    • 1) it is selective: contains crystal violet and bile acids which inhibit the growth of gram +ve bacteria
    • 2) it is differential: contains a pH indicator; lactose fermenters make acid turning the media red; otherwise it stays clear
  17. Answer the following about non-fermentive GNB
    1) _______ GN rods
    2) ______ aerobes
    3) non _____ fermenters
    4) Many are ______ to lots of Abx
    5) some are ______ positive (vs. enterobactereceae)
    6) Important ______ infections
    • 1) Skinny
    • 2) Obligate
    • 3) lactose
    • 4) resistant
    • 5) oxidase
    • 6) nosocomial
  18. What are the 3 L's for psuedomonas
    • Landscape: GNB, lactose non-fermenter, oxidase positive, found in hospitals (ventilators), burn patients, 
    • Landmarks: lung infections in cystic fibrosis, bacteremia in neutropenic patients
    • Landmines: resistant to most Abx except gentamycin and a few others.
  19. The 3 L's for Stenotrophomonas.
    • Landscape: GNB, non-fermenter, oxidase negative
    • Landmarks: treat with Septra
    • Land mines: resistant to most Abx
  20. Fill in the blanks regarding the HACEK organism:
    1) Normal flora of __________
    2) _________ is an important risk factor in HACEK
    3) most commonly implicated in ________
    • 1) Upper resp tract
    • 2) periodontal disease
    • 3) culture negative endocarditis
  21. Describe the life cycle of a virus
    • 1) adsorption: attach to host cell
    • 2) penetration/uncoating: virus enters host cell and shoots its nucleic acid inside
    • 3) gene expression: viral genes expressed to make more viruses in hijacked cell
    • 4) Assembly: new intact viruses inside cell
    • 5) Release: virus particles exit host cell
  22. 4 possible outcomes of viral infection
    • 1) lytic (acute) infection
    • 2) persistant (chronic) infection
    • 3) latent infection
    • 4) host cell transformation
  23. What are 5 reasons that viruses are so hard to treat?
    • 1) viral latency in recurrent infection
    • 2) They are inside of cells
    • 3) They use the cell's machinery to replicate
    • 4) They display host antigens on exterior
    • 5) Rapid mutation with rapid replication
  24. What are the three categories of AV agents?
    • 1) Virucidal: directly inactivate intact viruses
    • 2) Immunomodulatory: augment or modify host response to virus
    • 3) Direct Acting: inihibit viral replication on a cellular level
  25. What are the 5 indications for IFN-alpha therapy
    • 1) HBV chronic
    • 2) HCV chronic
    • 3) HPV infection
    • 4) HIV?
    • 5) non-infectious: ITP, some leukemias
  26. 6 classes of HIV antiretrovirals avail
    • 1) NRTIs (nucleotide/side analogue reverse transcriptase inhibitor)
    • 2) non-NRTI's
    • 3) protease inhibitors
    • 4) fusion inhibitors
    • 5) entry inhibitors
    • 6) Integrase inhibitors
  27. How does AmpB work?
    binds to ergosterol on the fungal cell membrane and causes holes
  28. When should you use lipid AmpB?
    • 1) refractory to conventional AmpB
    • 2) patient intolerant to AmpB
    • 3) renal dysfunction
    • 4) selected difficult to treat pathologies
  29. what is the first line treatment for candidiasis?
    fluconazole
  30. First line treatment in invasive aspergilliosis
    Voriconazole
  31. 4 things that are true of exotoxins but not endotoxins
    • 1) must be released from cells to have toxic effects
    • 2) require specific receptors
    • 3) small doses are lethal
    • 4) most act remotely from the site of infection
  32. 6 modes of action for exotoxins
    • 1) pore formation
    • 2) alteration of cytoskeleton
    • 3) inhibition of protein synthesis
    • 4) activate second messenger pathways
    • 5) proteases
    • 6) activate immune response (superantigen)
  33. How does botulism work?
    • 1) starts with cranial nerve symptoms and then descending paralysis
    • 2) floppy people
    • 3) Affects the SNARE proteins that are responsible for the release of ACh
    • 4) irreversibly bound, need to grow new nerve terminals
    • 5) most potent toxin known to man
  34. How does tetanus work?
    • 1) muscle rigidity and spasms
    • 2) blocks the release of inhibitory neurotransmitters (e.g. GABA)
  35. How does Diptheria work?
    • 1) terminates protein synthesis
    • 2) toxicity is conferred by a bacteriophage (need this)
    • 3) causes tissue destruction (remember psuedomembrane)
  36. How does bordetella pertussis (whooping cough) work?
    • 1) there are multiple toxins at work, complicated
    • 2) basically attacks the mucociliary escalator
  37. How does cholera work?
    • 1) volume depleted because of the profuse watery diarrhea
    • 2) It affects the secondary messenger, causes Cl to be shunted out of the cell, the Na and H2O follow
    • 3) requires bacteriophage
  38. What are the features of untreated leprosy (lepromatous vs tuberculoid)
    • Lepromatous provides little or no CMI response.
    • Tuberculoid produces a vigorous CMI response.
  39. What is the treatment of active TB?
    • They are RIPE for treatment:
    • R: Rifampin
    • I: Isoniazid
    • P: Pyrazinamide
    • E: Ethambutamol
  40. What are the 3 objectives in treating TB?
    • 1) rapid killing of TB bacilli (reduce mortality, morbidity, contagousness)
    • 2) prevent the emergence or existence of drug resistence
    • 3) Prevent relapse after therapy and achieve cure
  41. what is the difference between fever and hyperthermia?
    fever - the setpoint of body temp has been altered

    hyperthermia - you go above the setpoint of the body
  42. What are the 4 categories of fever of unknown origin? Details. temperature
    Temp for all of these is >38.3

    Classical FUO: >3 wks, or at least 3 outpatient visits, or 3 days in hospital

    Nosocomial FUO: 3 day of investigation with 2 days of cultures

    neutropenic FUO: same as nosocomial with neutrophil count <500/ml

    HIV-associated FUO: same as nosocomial with HIV, with > 4weeks duration outpatients or >3dys inpatient
  43. What are the 5 main etologic causes of FUO in order of prevalence?
    • -Infectious
    • -neoplastic causes
    • -connective tissue diseases (SLE, RA, etc)
    • -miscellaneous (drugs, etc)
    • -no diagnosis
  44. What are the 4 cancers that commonly present with fever (remember the 4H)
    • -hematologic
    • -hypernephroma: renal cell ca
    • -hepatic: 
    • -head: brain
  45. What are some peripheral signs of endocarditis (6)?
    • Roth spots: small ovoid hemorrhagic rings in retina
    • Janeway lesions: small painless microemboli on the palms or soles
    • Osler's nodes: painful, on thenar eminance
    • clubbing
    • splinter hemorrhages
    • splenomegaly
    • petechial rashes
  46. what is the most common cause of native valve endocarditis?
    viridians group strep
  47. What is the most common cause of prothetic valve endocarditis?
    • CONS (late)
    • S. Aureus (within first 12 months)
  48. What is the hallmark of bacterial endocarditis?
    continuous bacteremia
  49. What are the clinical features of infectious endocarditis (recall the FROM JANE mnemonic)
    • Fever
    • Roth's spots
    • Osler's nodes
    • Murmur
    • Janeway lesions
    • Anemia
    • Nail bed hemorrhages (aka. splinter hemorrhages)
    • Emboli
  50. Out of all the GI parasites, which is the one that can make you the sickest?
    Entamoeba histolytica - because it can cause symptoms outside of the gut
  51. What three major pathological findings do you find in entamoeba histolytica?
    • large flask-shaped ulcers in in the large intestine
    • liver abscesses 
    • lung abscesses
  52. What is the treatment for entamoeba histolytica (invasive disease and for asymptomatic cyst passers) and giardia lambia?
    • invasive: metronidazole
    • asymptomatic: iodoquinol (need a compounding pharmacy)

    giardia: metronidazole
  53. What are the three pathological flagellates?
    • Giardia lamblia
    • dientamoeba fragilis
    • trichomonas vaginalis
  54. What is the crucial point to know about D. fragilis?
    they can parasitize helminth eggs
  55. What are the three critical concepts in helminth infections
    -worm burden: number of ADULT parasites in host

    -autoinfection: completes their whole lifecycle in the host (pinworm and strongyloides only)

    -systemic migration: eosinophilia, rashes, dyspnea
  56. What are the two P's in helminth stool examination
    • Preservative: submit in the correct vial
    • Provide clinical justification to justify microscopy
  57. What are the Sx you see with high worm burden?
    • GI: abdo discomfort, bowel obstruction, +-diarrhea
    • Diet: malnutrition, hypoproteinemia(adema, ascites)
    • Mental: decreased IQ, cognitive impairment
  58. What are the 5 parameters of the Child-pugh classification of cirrhosis?
    Bili, albimin, INR, ascites, ecephalopathy
  59. What tests would you order with asymptomatic patients with elevated liver transaminases
    • Hep B surface antigen
    • Hep C antibodies
    • Anti smooth muscle, antinuclear Abs
    • Copper studies
    • Ferritin
    • alpha1 AT phenotype
  60. What are the 4 most common respiratory viruses?
    PAIR

    • Paraflu
    • Adeno
    • Influenza (flu)
    • RSV
  61. How can you differentiate RSV and paraflu?
    • RSV: bronchiolitis, pneumonia > croup, URI
    • paraflu: croup, laryngitis, URI > bronchiolitis, pneumonia
  62. what is the incubation time for the PAIRs viruses, enterovirus, hantavirus?
    • Paraflu: 2.5 days
    • Adeno: 5.5 days
    • Influenza: 1.5 d (A), 0.5 d (B)
    • RSV: 4.5 days

    • entero: 3-6 days
    • hanta: usually 2-4 weeks
  63. What is the difference between antigenic drift and antigenic shift? how does a shift happen
    drift: point mutations in H or N, allows to re-infection every year

    shift: Completely different H and N, no immunity at all, causes pandemics. Animal and human virus combine in pig cell to make a new virus.
  64. What are the "common cold" viruses?
    corona viruses, rhinovirus
  65. How would you treat influenza and adeno virus? What about the rest of the rest of the resp viruses?
    Influenza: neuramidase inhibitor for A or B (osetamvir, zanamivir), vaccine (2 A's and a B) for prophylaxis

    Adeno: Cidofovir only in immunocompromised patients

    The rest of them have no effective clinical treatment
  66. What are the three stages of bordella pertussis (whooping cough)
    • 1-2 weeks of cold symptoms
    • 2-4 weeks of paroxysmal cough (+- the "whoop")
    • Convalesce for 1-2 weeks: slow recovery with chance of rebound cough
  67. What are the three major bacterial causes of acute otitis media? 4 viral causes?
    bacterial: pneumoniae>H. flu>>M. Catarrhalis

    viral: PAIR (paraflu, adeno, influenza, RSV)
  68. What bugs (bacteria, viral, fungal) cause pharyngitis
    • Bacterial: Group A strep, gonorrhea
    • Viral: rhinovirus + PAIRs viruses + others
    • Fingal: Candida albicans
  69. What are the usual bugs involved in ludwig's angina?
    Gp A strep, viridins (alpha) strep, oral anaerobes
  70. List the 4 fastidious GNB
    • legionella
    • HACEK
    • borditella
    • hemophilias
  71. 4 cardiac complications of endocarditis?
    • 1) destruction of valve leading to free regurg
    • 2) CHF
    • 3) heart block
    • 4) pericarditis
  72. When should you treat B. hominis?
    • 1) patient is symptomatic
    • 2) no other parasites identified
    • 3) lots of them seen in stool
  73. Describe what a positive test for HBsAg, HBsAb, HBcIgM, and HBcIgG
    • HBsAg: infection, either chronic or active
    • HBsAb: immune, either through a past resolved infection or a vaccine
    • HBcIgM: acute infection
    • HBcIgG: chronic infection or immunity due to past resolved infection
  74. How does the CURB-65 pneumonia severity index work?
    • Confusion - 1 point
    • Urea > 7 mmol - 1 point
    • RR > 30 beats per min - 1 point
    • Blood pressure low - <90 sys., <60 dia - 1 pt
    • 65 or older - 1point
    • 0-1: treat as outpatient
    • 2: consider hosp.
    • 3-5 consider ICU
  75. Name the top 3 pathogens for both CAP and HAP
    • CAP: S. pneumoniae, Mycoplasma, Chlamydophile
    • HAP: enteric GN rods (e.g. e. coli), psuedomonas, S. aureus

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