Med Micro exam 1

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Med Micro exam 1
2015-09-24 12:59:41
med micro

med micro
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  1. transient bacteremia
    minor mucocutaneous breaches allowing acces by normal microbiota or pathogens

    • brushing/flossing
    • BM, hemorrhoids
    • endoscopy
    • GI infection
    • UTI
  2. intermittent bactermia
    showering of bloodstream from established localized but severe infection

    • staphylococcal abscess
    • pneumococcal pnemonia
  3. continuous bacteremia
    source of infection with direct access to blood

    • infective endocarditis
    • IV catheter/line infection
  4. Microbial products stimulate host response in sepsis
    • Pathogen-associated molecular patterns: (PAMPs)
    • Endotoxin/ lipopolysaccharide (LPS) in Gram -
    • teichoic acids in gram +
    • peptidoglycan in most bacteria
    • glucans in fungi

    Superantigens: toxic shock syndrome toxins (TSST), produced by some staphylococcal and streptococcal species and strains
  5. Host response in sepsis
    • complement cascade --> inflammation
    • kinins--> hypotension
    • coagulation cascade --> DIC
    • Cellular responses --> stimulation of pattern recognition receptors by PAMPs, cytokines --> fever, innate and adaptive immune responses
    • hyperstimulation may be follow by hypoactivity
  6. microbes commonly isolated from "true positive " BC's
    • Escherichia coli and other enterobacteriaceae
    • staphylococci
    • streptococci
    • pseudomonas
  7. most common isolates from nosocomial infections
    • coagulase negative staphylococci including staphylococcus epidermidis
    • staphylococcus aureus
    • enterococci
    • candida
  8. multiorgan failure
    • acidosis- blood pH <7.35
    • lung- pulmonary edema, cyanosis
    • kidney- oliguria, anuria
    • lier- jaundice
    • heart- CHF, septic shock usually characterized by high cardiac output at start
    • CNS- altered mental status
  9. contamination of blood draw
    • common on skin: can contaminate sample
    • staphylococci
    • streptococci
    • pseudomonas

    higher probability of IV being contaminated
  10. neonate infections
    • Vaginal microbes: during delivery
    • group B strep (streptococcus agalactia)
    • -leading cause of neonatal sepsis and meningitis, can have neurological deficits after
    • e coli
    • enterococcus spp
    • neisseria gonorrhoeae
    • chalmydia trachomatis
    • salmonella

    • transplacental transmission: with or w/o symptoms
    • listeria monocytogenes (foodborne)
    • toxoplasma gondii
  11. granulocytes
    • Neutrophils: PMN
    • responsible against infection
    • produced in bone marrow, migrate to tissues where needed
    • phagocytic, form pus, first to inflammation via chemotaxis
    • eosinophils: allergies and parasites
    • basophils: WBC releases histamine
    • natural modulator of inflammatory response
  12. lymphocyte
    • Natural Killer cells: patrol body for pathogens
    • binds to enemy cells and releases perforins, granzymes. destroys compromised host cells
    • T cells: mature in the thymus
    • recognize antigens presented by APC's
    • Helper T cells: nonspecific defense and humoral and cellular immunity
    • recognize antigen fragments from APC's with MHCII proteins, secrete interleukins that activate B, Tc, and NK cells
    • Cytotoxic T cells: cellular immunity, directly attach and destroy enemy cells
    • recognized MHCI cells
    • B cells: identifies pathogens by its antibodies, serve as APC, produces antibodies in response
    • B cell receptor (immunoglobulin, antibody) is secreted
  13. Innate immunity
    • immediate response, initial defense
    • non-specific, no memory, not enhanced by immunization
    • includes cellular components- neutrophils, macrophages, dendritic cells, NK cells and humoral components - complement, cytokines, antimicrobial peptides
  14. Adaptive immunity
    • slower response, antigen specific
    • enhanced by immunization, generates memory, rapid response on subsequent exposures
    • includes T and B lymphocytes and antibodies
  15. Monocytes/macrophages
    • migrate to tissues and become macrophages and includes dendritic cells
    • antigen presenting cells in T cell activation by phagocytizing microbes, processing antigen, and presenting it
    • MHC class II
  16. Plasma cells
    • develop from B cells that have been activated by helper T cells
    • synthesize and secrete antibodies
  17. Dendritic cells
    • branched, mobile APC's of the skin, mucous membranes and lymphatic tissues
    • internalize antigen, migrate to lymph node and present to Th and Tc cells
  18. MHC proteins
    • proteins on APC surface that are unique to each person labeling those cells as yours
    • MHCI: found on surface of all nucleated host cells
    • recognized by CD8 T lymphocytes
    • recognized by cytotoxic T cells
    • presents endogenous cytosolic antigens (viral antigens, tumor antigens)

    • MHCII: found on surface of host APC's
    • presents exogenous antigens in endocytic pathway (phagocyosed particle antigens)
    • recognized by CD4 T lymphocytes
    • recognized by T helper cells
    • foreign antibodies
  19. Active vs passive immunity
    • Natrually acquired active is infection
    • Naturally acquired passive is transplacental, colostrum, or receiving ab
    • Artificial active is vaccine
    • Artificial passive is ab injections, immunoglbulin tx for autoimmune,
  20. Immunoglobulin
    • IgG: 4 subclasses
    • predominant in serum, also in secretions, only one that crosses placenta
    • monomeric
    • IgM: appears early in immune response, dominant one in it
    • strong agglutinating and complement fixation abilities
    • can be pentameric
    • IgA: 2 subclasses
    • found in mucosal secretions and surfaces as well as serum
    • dimeric or large polymers
    • IgE: monomer
    • attaches to mast cells and basophils
    • stimulates histamine release
    • important in parasite immunity
    • IdD: monomer
    • activation of B cells by antigens

    • antibodies exert effects via
    • neutralization: blocking viral adhesion, inactivating bacterial toxin
    • opsonization: promoting phagocytosis
    • complement activation: causing lysis via mAC, promoting phagocytosis
  21. inflammation
    • microbe stimulates macrophages and activates complement
    • macrophage produces cytokines, chemokines, and other mediators
    • complement activation results in production of C3a, C5a - both anaphylatoxins and chemotaxins
    • cardinal signs are redness, swelling, heat, and pain
    • begins with vasoconstriction, followed by increase in vascular permeability
    • upregulation of surface adhesion molecules on endothelium and PMN
  22. complement
    • microbe stimulates macrophages and activates complement
    • proteins that promote phagocytosis and cytolysis of pathogens
    • activate and attract PMN's and macrophages
    • stimulate basophils and mast cells to secrete inflammatory chemicals

    • 3 pathways: classical, alternative, lectin
    • classical- antibody molecule, specific immunity, Ag-Ab exposes complement binding sites
    • alternative- C3b binds to targets, triggers cascade, non-specific, spontaneous
    • lectin- plasma proteins bind to carbs (microbe surface), sets off cascade leading to C3b production

    • products of complement activation
    • C3a and C5a- anaphylatoxins (mast cell degredation, histamine release) and chemotaxins (attracts WBC's)
    • C3b- opsonization - opsonin coats particle and facilitates uptake by phagocytes
  23. integirin
    protein that links outside of cell with its interior
  24. interleukin
    produced mainly by T cells, and macrophages to stimulate other leukocytes
  25. epitope
    • found on surface of antigen
    • determines specificity of antibody reaction and where antibody binds
  26. therapeutic index
    vancomycin and aminoglycosides have toxic level close to therapeutic level
  27. antibiotic spectrum of activity
    • Narrow spectrum: isoniazid
    • broad: amoxicillin
    • tetracycline
    • chloamphenicol
    • very broad: metronidazole
  28. Sensitivity
    • Proportion of individuals with disease that are correctly identified
    • TP/ (TP+FN)
  29. Specificity
    • Proportion of individuals without disease correctly identified
    • TN/ (TN +FP)
  30. Positive predicative value
    Negative predictive value
    • Reliability of a positive test to identify diseased individual
    • TP / All positives 
    • Negative is reverse
  31. cultures
    • some obligate intracellular microbes may be cultured in host cells in tissue culture
    • some viruses
    • chalmydia
    • syphilis can grow in rabbit
    • mycobacterium leprae (leprosy) grow in armadillos
  32. agglutination tests
    • streptococcus pneumoniae- urinary antigen
    • cryptococcal antigen- csf, serum
    • legionella- urinary antigen
    • c diff toxin- stool
  33. limulus amebocyte lysate (LAL) assays
    • For gram neg LPS endotoxin or fungal beta glucan
    • non-invasive, serum
    • PAMPs are targets of innate immune
    • gram neg bacteria or fungi including CANDIDA
    • sensitivity up to 90
    • specificity 84-100
  34. Gram pos/neg
    • Positive: bacteria
    • staphylococcus
    • steptococcus
    • bacilli
    • clostridium
    • listeria
    • bacillus

    • Neg: bacteria
    • e. coli
    • salmonella
    • shigell
    • enterobacteriaceae
    • pseudomonas
    • heliobacter
  35. Visualization
    • microscopy, istopathology, staining, bright field microscopy
    • gram stain for routine bacteria
    • ziehl-neelsen stain for acid-fast mycobacteria
    • silver stain for fungi
    • KOH prep for fungi
    • saline wet mount for motile trichomonas vaginalis
    • auramine stain for mycobacteria
    • calcofluor white stain for fungie
  36. Prevalence
    • Rate at which a disease is found in a population
    • TP + FN / everything
    • PPV is higher for a test with higher prevalence. NPV is higher for lower prevalence
  37. Clostridium difficile
    • Anaerobic gram pos sporulating rod
    • found in soil, water, some normal gut microbiota

    • clinical range: for C diff
    • Asymptomatic
    • enteric infection- diarrhea, cramps, fever
    • pseudomembranous colitis- severe colitis, bloody diarrhea, ulcers, perfs, toxic megacolon, life threatening

    • Diagnose: c diff
    • PMN's in stool from inflammation
    • aerobic stool culture negative for other causes
    • anaerobic stool culture when done right may be positive
    • Leukocytosis (elevated WBC)
    • Stool sample pos for c diff toxins by ELISA or toxin genes by PCR

    • Treatment: for C diff diarrhea
    • discontinue previous abx
    • add new treatment with another abx- metronidazole for mild to moderate, vancomycin for more severe (but save for MRSA)
    • add probiotic therapy

    • Treatment: for C diff with pseudomembranous colitis
    • donor stool transplant
    • partial or complete colectomy
  38. abx targets
    • Cell wall synthesis: targets peptidoglycan cell wall that we don't have
    • d-cycloserine
    • vancomycin
    • bacitracin
    • penicillins
    • cephalosporins
    • cephamycins
    • Protein synthesis: 50S inhibitors and 30S inhibitors
    • erythromycin
    • choramphenoicol
    • cindamycin
    • lincoycin
    • 30- tetracyclines
    • aminoglycosides- gentamiciin, kanamycin, streptomycin, tobramycin
    • RNA polymerase: rifampicin
    • DNA synthesis: metronidazole
    • cytoplasmic membrane/phospholipid: polymyxins
    • Folate synthesis: TMP/sulfa
    • Fatty acid synthesis: isoniazid
  39. Threatening bacteria
    • Urgent: clostridium difficile
    • carbapenem- resistant enterobacteriaceae
    • drug resistant neisseria gonorrhoeae

    • Concerning: vancomycin resistant staphyloccoccus aureus
    • erthromycin resistant group A strep
    • clindamycin resistant group B strep
  40. UTI - agents of descending infection
    • hematogenous spread: from blood
    • staphylococcus aureus
    • candida albicans
  41. Lower UTI vs upper UTI
    • cystitis: of the bladder
    • dysuria
    • frequency
    • urgency
    • sometimes suprapubic pain
    • pyelonephritis: kidneys
    • flank and CVA pain
    • fever sometimes
    • perineal pain in men (prostatisi)
  42. epitope
    • found on surface of antigen 
    • determines specificity of Ab rxn and where it will bind
  43. abx information
    • Aminoglycosides: low therapeutic index
    • Vancomycin: low therapeutic index
    • attacks cell wall synthesis
    • Isoniazid: narrow range
    • fatty acid synthesis
    • Amoxicillin: broad range
    • tetracycline: broad range
    • chloramphenicol: broad range
    • 50S inhibitor, affects protein synthesis
    • metronidazole: very broad range
    • used to treat c diff
    • attacks DNA synthesis
  44. microbe info
    • clostridium difficile: main cause of abx
    • associated diarrhea
    • Staphylococcus aureus: can cause ADD
  45. Pulmonary aspergillosis
    25-30% have no symptoms usually due to neutropenia and lack of host response
  46. UTI ascending infection
    • E coli- gram negative rod
    • other: enterobacteriaceae
    • proteus spp
    • profidencia
    • kelbsiella
    • serratia

    • Vaginal colonizers
    • staphylococcos saprophyticus
    • enterococcus
    • candida albicans
  47. Common medical bacteria