Bacteria Background

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Bacteria Background
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  1. Peptidoglycan
    • Function:
    • -rigid support
    • -protects against osmotic pressure

    • Chemical composition:
    • -sugar backbone, cross linked peptide side chains (by transpeptidase)

  2. Cell wall/Cell membrane
    • -outer layer in GRAM POSITIVE
    • -major surface antigen
    • -contains lipoteichoic acid (induces TNF and IL1)
  3. Outer Membrane
    • -outer layer in GRAM NEGATIVE
    • -Site of endotoxin (LPS)
  4. LPS
    • -Lipid A: induces TNF and IL1
    • -O polysaccharide: antigen
  5. Ribosome
    50S and 30S subunits
  6. Periplasm
    • -GRAM NEGATIVE
    • -space btwn the cytoplasmic membrane and outer membrane
    • -contains beta lactamases
  7. Capsule
    • -protects against phagocytosis
    • -made of polysaccharides (except B. anthracis, which is made of protein)
  8. Pilus/Fimbria
    • -adherence to cell surface
    • -sex pilus during conjugation
  9. Spore
    -resistant to dehydration, heat and chemicals
  10. Plasmid
    -contains genes: abx resistance, enzymes, toxins
  11. Glycocalyx
    • -adherence to surfaces (esp foreign surfaces)
    • -polysaccharide
  12. Bacterial Virulence Factors
    Protein A: binds Fc region of Ig and prevents opsonization and phagocytosis (S. aureus)

    • IgA Protease: cleaves IgA to colonize respiratory mucosa
    • "SHiN"
    • S pneumo
    • H influenza
    • Neisseria

    M protein: helps prevent phagocytosis (Group A strep)
  13. Cell Wall


    • GRAM POSITIVE ONLY: lipoteichoic acid
    • GRAM NEGATIVE ONLY: Endotoxin/LPS, Periplasmic space
  14. GRAM POSITIVE Cocci
    • Staphylococcus
    • Streptococcus
  15. GRAM NEGATIVE Cocci
    Neisseria
  16. GRAM POSITIVE Bacilli
    • Clostridium
    • Corynebacterium
    • Bacillus
    • Listeria
    • Mycobacterium (acid fast)
    • Gardnerella (Gram variable)
  17. GRAM NEGATIVE Bacilli: Enterics
    • "CEEK ShYPS"
    • Campylobacter
    • E. Coli
    • Enterobacter
    • Klebsiella

    • Shigella
    • Yersinia
    • Proteus
    • Salmonella

    • Serratia
    • Vibrio
    • Helicobacter
    • Pseudomonas
    • Bacteroides
  18. GRAM NEGATIVE Bacilli: Respiratory
    • Haemophilus
    • Legionella
    • Bordetella
  19. GRAM NEGATIVE Bacilli: Zoonotic
    • Francisella
    • Brucella
    • Pasteurella
    • Bartonella
  20. GRAM POSITIVE Branching Filamentous
    • Actinomyces
    • Nocardia
  21. GRAM NEGATIVE Pleomorphics
    • Rickettsiae
    • Chlamydiae
  22. GRAM NEGATIVE Spiral
    • Spirochetes:
    • Leptospira
    • Borrelia
    • Treponema
  23. NO CELL WALL (No Gram stain)
    Mycoplasma
  24. Bugs that don't Gram stain well
    "These Rascals May Microscopically Lack Color"

    • Treponema (thin)
    • Rickettsia (intracellular)
    • Mycobacteria (high lipid content)
    • Mycoplasma (no cell wall)
    • Legionella (primarily intracellular)
    • Chlamydia (intracellular)
  25. Giemsa Stain
    "Certain Bugs Really Try my Patience)

    • Chlamydia
    • Borrelia
    • Rickettsiae
    • Trypanosomes
    • Plasmodium
  26. Periodic Acid Shiff (PAS) Stain
    "PASs the sugar"

    Stains glycogen

    Used to diagnose Whipple Disease
  27. Ziehl-Neelsen Stain (carbol fuchsin)
    Acid fast organisms

    • Mycobacterium
    • Nocardia
  28. India Ink Stain
    Cryptococcus neoformans
  29. Silver Stain
    • Fungi (pneumocystis)
    • Legionella
    • H. pylori
  30. Special Culture Requirements
    H flu: Chocolate agar (Factors V = NAD+, X = hematin)

    Neisseria: Thayer Martin (Vancomycin, Polymyxin, Nystatin)

    Bordetella pertussis: Bordet-Gengou (potatoe agar)

    C. diphtheriae: Tellurite plate, Loffler's media

    M. tuberculosis: Lowenstein-Jensen agar

    M. pneumoniae: Eaton's agar

    Lactose fermenting enterics: pink on MacConkey's agar

    E Coli: EMB agar (green metallic sheen)

    Legionella: charcoal yeast agar buffered with cysteine and iron

    Fungi: Sabouraud's agar ("Sab's a fun guy!")
  31. Obligate aerobes
    "Nagging Pests Must Breathe"

    • Nocardia
    • Pseudomonas aeruginosa
    • Mycobacterium tuberculosis
    • Bacillus
  32. Obligate Anaerobes
    "Anaerobes Can't Breathe Air"

    • Clostridium
    • Bacteriodes
    • Actinomyces

    • -Lack catalase and/or superoxide dismutase
    • -Generally foul smelling
    • -difficult to culture
    • -produce gas in tissue (CO2, H2)
    • -normal flora in GI tract, pathogenic elsewhere

    "AminO2glycosides are ineffective against anaerobes because these abx require O2 to enter bacterial cell"
  33. Obligate Intracellular Bugs
    "Stay inside when it is Really Cold"

    • Rickettsia
    • Chlamydia
    • (can't make own ATP)
  34. Facultative Intracellular Bugs
    "Some Nasty Bugs May Live FacultativeLY"

    • Salmonella
    • Neisseria
    • Brucella
    • Mycobacterium
    • Listeria
    • Francisella
    • Legionella
    • Yersinia
  35. Encapsulated Bacteria
    • Positive quellung reaction
    • "Quellung = capsular swellung"

    • "SHiNE SKiS"
    • Strep pneumo
    • H influenza B
    • N. meningitidis
    • E coli

    • Salmonella
    • Klebsiella
    • Strep (Group B)

    Opsonized then cleared by spleen

    Asplenia at increased risk: vaccinate!
  36. Catalase Positive
    • You need PLACESS for your cats"
    • Pseudamonas
    • Listeria
    • Aspergillus
    • Candida
    • E Coli
    • S. aureus
    • Serratia

    Catalase degrades H2O2

    People with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with these organisms
  37. Bacterial Vaccines
    protein conjugated to polysccharide capsule antigen (allows presentation to T cells --> class switching)

    • Pneumovax (no conjugated protein)
    • Prevnar (conjugated)
    • HIB (conjugated)
    • Meningococcal (Conjugated)
  38. Urease-Positive Bugs
    "CHuck Norris hates PUNKSS"

    • Cryptococcus
    • H. pylori
    • Proteus
    • Ureaplasma
    • Nocardia
    • Klebsiella
    • S. epidermidis
    • S. saprophyticus
  39. Pigment Producing Bacteria
    • Actinomyces israelii: yellow sulfur granules
    • "Israel has yellow sand"

    • S.aureus: yellow pigment
    • "aureus = Latin for gold"

    • Pseudomonas aeruginosa: blue-green pigment
    • "Aerugula is green"

    • Serratia marcescens: red pigment
    • "red maraschino cherries"
  40. Exotoxins
    • -Gram positive and Gram negative bacteria
    • -secreted from cell
    • -polypeptide
    • -genes in plasmid or bacteriophage
    • -high toxicity (may be fatal)
    • -induces antitoxins (antibodies)
    • -toxoids used as vaccines
    • -destroyed at 60C (except staph)

    EG: tetanus, botulism, diphtheria
  41. Endotoxins
    • -Gram negative outer cell membrane component
    • -Not secreted from cell (released when lysed)
    • -LPS
    • -genes in bacterial chromosome
    • -low toxicity (fatal at very high doses)
    • -cause fever and shock
    • -induces TNF and IL1
    • -poorly antigenic
    • -no vaccines
    • -stable at 100C for 1 hour


    EG: Meningococcemia, sepsis by GN rods
  42. Exotoxins that Inhibit Protein Synthesis
    • -Diphtheria toxin (Cornebacterium diphtheria)
    • -Exotoxin A (Pseudomonas)
    • -Shiga toxin (Shigella)
    • -Shiga-like toxin
  43. Diphtheria toxin
    -exotoxin

    -in Corynebacterium diphtheriae

    • Mechanism:
    • -inactivate EF2

    • Presentation:
    • -Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
  44. Exotoxin A
    -exotoxin

    -in Pseudomonas aeruginosa

    • Mechanism:
    • -inactivates EF2

    • Presentation:
    • -Host cell death
  45. Shiga Toxin (ST)
    -exotoxin

    -in Shigella spp

    • Mechanism:
    • -inactivate 60S ribosome (remove adenine from rRNA)

    • Presentation:
    • -GI mucosal damage --> dysentery
    • -enhance cytokine release --> HUS
  46. Shiga-like toxin (SLT)
    -exotoxin

    -in EHEC (including O157:H7)

    • Mechanism:
    • -inactivate 60S ribosome (remove adenine from rRNA)

    • Presentation:
    • -enhance cytokine release --> HUS

    ***unlike shigella EHEC doesn't invade host cells
  47. Exotoxins that increase fluid secretion
    • -Heat-labile toxin (LT)
    • -Heat-stabile toxin (ST)
    • -Edema factor
    • -cholera toxin
  48. Heat-Labile Toxin (LT)
    -exotoxin

    -in ETEC

    • Mechanism:
    • -overactivates AC --> increased cAMP --> increased Cl- secretion in gut

    • Presentation:
    • -watery diarrhea

    "Labile in the Air (AC), Stable on the Ground (GC)"
  49. Heat-Stable Toxin (ST)
    -exotoxin

    -in ETEC

    • Mechanism:
    • -overativates GC --> increased cGMP --> decreased resorption of NaCl in gut

    • Presentation:
    • -watery diarrhea

    "Labile in the Air (AC), Stable on the Ground (GC)"
  50. Edema Factor
    -exotoxin

    -Bacillus anthracis

    • Mechanism:
    • -mimics AC --> increase cAMP

    • Presentation:
    • -characteristic edematous borders of black eschar in cutaneous anthrax
  51. Cholera Toxin
    -exotoxin

    -Vibrio cholerae

    • Mechanism:
    • -overactivates AC by permanently activating Gs --> increased cAMP --> increased Cl- secretion

    • Presentation:
    • -voluminous rice water diarrhea
  52. Exotoxins that inhibit phagocytic ability
    -Pertussis toxin
  53. Pertussis Toxin
    -exotoxin

    -Bordetella pertussis

    • Mechanism:
    • -overactivates AC by disabling Gi --> impaired phagocytosis

    • Presentation:
    • -Whooping Cough in children
    • -100 day cough in adults
  54. Exotoxins that inhibit release of NT
    • -Tetanospasm
    • -Botulinum Toxin
  55. Tetanospasm
    -exotoxin

    -Clostridium tetani

    • Mechanism:
    • -cleave SNARE protein required for NT release
    • -prevents release of inhibitory NTs (GABA and Glycine) in spinal cord

    • Presentation:
    • -muscle rigidity and "lock jaw"
  56. Botulinum Toxin
    -exotoxin

    -Clostridium botulinum

    • Mechanism:
    • -cleave SNARE protein required for NT release
    • -prevents release of stimulatory (ACh) release at NMJ

    • Presentation:
    • -Flaccid paralysis
    • -floppy baby
  57. Exotoxins that lyse cell membranes
    • -alpha toxin
    • -streptolysin O
  58. Alpha Toxin
    -exotoxin

    -Clostridium perfringens

    • Mechanism:
    • -phosophlipase: degrades tissue and cell membranes (PLC)

    • Presentation:
    • -"gas gangrene" and hemolysis (double zone of hemolysis on blood agar)
  59. Streptolysin O
    -exotoxin

    -Strep pyogenes

    • Mechanism:
    • -protein that degrades cell membrane

    • Presentation:
    • -lyses RBCs --> beta hemolysis

    *** host antibodies against toxin (ASO) used to diagnose rheumatic fever
  60. Exotoxins that are Superantigens that cause shock
    • -Toxic Shock syndrome toxin 1
    • -Exotoxin A'
  61. Toxic Shock Syndrome Toxin I (TSST-1)
    -exotoxin

    -Staph aureus

    • Mechanism:
    • -bring MHCII and TCR in proximity --> overwhelming release of IFNg and IL2

    • Presentation:
    • -TSS: fever, rash, shock

    • Scalded Skin Syndrome (exfoliative toxin)
    • Food Poisoning (enterotoxin)
  62. Exotoxin A'
    -exotoxin

    -Strep pyogenes

    • Mechanism:
    • -bring MHCII and TCR in proximity --> overwhelming release of IFNg and IL2

    • Presentation:
    • -TSS: fever, rash, shock
  63. Endotoxin Mechanism and Presentation
    • -LPS
    • -especially Lipid A

    • Mechanism:
    • 1. Activate macrophages
    •      -IL1 (fever)
    •      -TNF (fever, hypotension)
    •      -NO (hyptension)
    • 2. Activate C'
    •      -C3a (hypotension, edema)
    •      -C5a (NP chemotaxis)
    • 3. Activates tissue factor
    •      -coagulation cascade (DIC)

    • "ENDOTOXIN"
    • Edema
    • NO
    • DIC/Death
    • Outer Membrane
    • TNFa
    • O-antigen
    • eXtremely heat stable
    • IL1
    • Neutrophil chemotaxis
  64. Bacterial Growth Curve
    Lag Phase: metabolic activity without division

    Exponential/Log Phase: rapid cell division (PCNs and cephalosporins act here)

    Stationary Phase: nutrient depletion slows growth, spore formation in some bacteria

    Death: prolonged nutrient depletion, waste products lead to death

  65. Transformation
    -take up naked DNA from environment (ie: from lysis)

    =competent

    • Many bacteria including "SHiN":
    • S pneumo
    • H influenza
    • Neisseria
  66. Conjugation
    • F+ x F-
    • -F+ can replicate (pilus)
    • -plasmid (dsDNA) ONLY transferred

    • Hfr x F-
    • -F+ plasmid incorporated into bacterial chromosome (high frequency recombination cell)
    • -may also replicate flanking DNA-transfer of plasmid and chromosomal DNA
  67. Transposition
    • -DNA segment that can "jump" locations
    • -can transfer DNA from plasmid to chromosome and vice versa
    • -may include flanking chromosomal DNA (potential transfer to another bacterium)
  68. Transduction
    • 1. Generalized:
    • -"packaging" event
    • -lytic phage can lyse bacterial DNA
    • -may be incorporated into viral capsid and be transferred to another bacteria

    • 2. Specialized:
    • -"excision" event
    • -phage infects bacteria and incorporates into its DNA
    • -when the virus removes its DNA it may take flanking DNA with it
  69. Lysogeny, Specialized Conduction
    Genes for 5 bacterial toxins encoded in a lysogenic phage:

    "ABCDE"

    • ShigA-like toxin
    • Botulinum toxin
    • Cholera toxin
    • Diphtheria toxin
    • Erythrogenic toxin (Strep pyogenes)

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