Ch 1: General

Question 1

Normal Flora of the cutaneous surfaces of urethra and outer ear

Answer 1

1. staph epidermidis ** most important
2. Less important:
   - staph. aureus
   - corynebacteria (diphtheroids)
   - streptococci
   - anaerobes ie peptostreptococci, yeasts (candida spp)

Question 2

Normal Flora of the nose

Answer 2

1. staph aureus
2. Less important:
   - s. epidermidis
   - diptheroids
   - assorted streptococci

Question 3

Normal Flora of the oropharynx

Answer 3

1. viridans streptococci ie strep mutans (secretes a biofilm that glues it and other oral flora to teeth, producing dental plaque)
2. Less important:
   - assorted strep
   - nonpathogenic neisseria

Question 4

Normal Flora of the gingival crevices

Answer 4

1. anaerobes: bacteroides, prevotella, fusobacterium, streptococcus, actiomyces

Question 5

Normal Flora of the stomach

Answer 5

none

Question 6

Normal Flora of the colon

Answer 6

1. • babies: breast-fed only: bifidobacterium
   • Adult: bacteroides/prevotella (predominant organism), escherichia, bifidobacterium
2. Less important:
   - babies: lactobacillus, streptococci
   - adults: eubacterium, fusobacterium, lactobacillus, assorted gram - anaerobic rods, enterococcus faecalis, other strep

Question 7

Normal Flora of the vagina

Answer 7

1. lactobacillus
   * Group B strep colonize vagina of 15-20% of women and may infect infant during labor or delivery, causing septicemia and/or meningitis (as may E.coli from fecal flora)
2. Less important:
   - assorted strep, gram - rods, diphtheroids, yeasts, veillonella

Question 8

primary mechanism of adherence used by gram - cells

Answer 8

pili/fimbriae

Question 9

primary mechanism of adherence used by gram + cells

Answer 9

teichoic acids (basically pili for gram + org)

Question 10

biofilms are used by

Answer 10

• staph epidermidis
• strep mutans
• pseudomonas aeruginosa

Question 11

Bacterial Ribosome size and subunits

Answer 11

70s: 30s + 50s

Question 12

Fungi Ribosome size and subunits

Answer 12

80s: 40s + 60s

Question 13

Parasite Ribosome size and subunits

Answer 13

80s: 40s + 60s

Question 14

Cell Membrane sterols

1. virus
2. bacteria
3. fungi
4. parasites

Answer 14

Cell Membrane sterols

1. virus = no membrane
2. bacteria = no sterols (mycoplasma)
3. fungi = Ergosterol* major target for anti-fungal drugs
4. parasites = cholesterol

Question 15

Cell wall component

1. virus
2. bacteria
3. fungi
4. parasites

Answer 15

• Cell walls are found in prokaryotes and fungi:
  1. virus = no cell wall
  2. bacteria = peptidoglycan (gram + bacteria have thicker PG cell wall –> can retain crystal violet stain on gram stain; gram - bacteria have thin PG cell wall, can’t retain stain, are pink)
  3. fungi = chitin
  4. parasites = no cell wall
• DNA with histones, monocistronic mRNA, and 80S ribosomes are found in all eukaryotes.

Question 16

Prokaryotic or Eukaryotic?

Answer 16

bacteria = prokaryotic

fungi and parasites = eukaryotic

Question 17

HY Encapsulated organisms

Answer 17

Some Killers Have Pretty Nice Capsules
S: streptococcus pneumoniae
K: Klebsiella pneumoniae
H: Haemophilus influenzae
P: Pseudomonas aeruginosa
N: Neisseria meningitidis
C: Cryptococcus neoformans (fungus)
* all the rest are bacteria
* anti-phagocytic surface component (inhibits phagocyte uptake)

Question 18

Organisms with capsules/slime layers:

Answer 18

1. anti-phagocytic surface component (inhibits phagocyte uptake)

Question 19

Bacteria that evade intracellular killing

Answer 19

1. TB: inhibits phagosome-lysosome fusion

2. listeria quickly escapes phagosome into cytoplasm before phagosome-lysosome fusion

Question 20

Invasins

Answer 20

• surface proteins that allow an organism to bind to and invade normally non-phagocytic cells, thus escaping the immune system (bc non-killing cells don’t have killing mechanisms, so doesn’t need to fight to survive)
• ex) yersinia pseudotuberculosis (causes diarrhea)

Question 21

Type 3 Secretion systems

Answer 21

• tunnel from the bacteria to the host cell (macrophage) that delivers bacterial toxins directly to the host cell
• e. coli
• salmonella
• yersinia
• p. aeruginosa
• chlamydia

Question 22

cross-ran of bacteria-induced antibodies with tissue antigens –> disease
1. What type of hypersensitivity is this?

Answer 22

ex) Rheumatic fever

1. Type 2 hypersensitivity (bc antibodies binding directly to a cell/tissue)

Question 23

prion

Answer 23

Prions, or “slow viruses,” are not viruses at all but infectious proteins devoid of nucleic acid.

Question 24

Lipid A

Answer 24

• Lipid A is the toxic component of endotoxin or lipopolysaccharide, which makes up the outer membrane of all gram-negative bacteria.
• Capsules and exotoxins are produced by some gram-negatives and some gram-positives, but not all.
• Teichoic acids are possessed by all gram-positives.

Question 25

Which exotoxins causes lysis of cell membranes?

Answer 25

- The alpha toxins of Clostridium perfringens and Staphylococcus aureus are cytolytic and lyse cell membranes. - Endotoxin is not an exotoxin but an anatomic part of the gram-negative bacterial envelope

Question 26

Endotoxin

Answer 26

- LPS (part of outer membrane/cell envelope; secreted when kill bug) - part of gram-negative outer membrane - Toxic portion = Lipid A: generally not released until death of cell. - Exception: N. meningitidis, which over-produces outer membrane fragments - LPS is heat stable and not strongly immunogenic so it can't be converted to a toxoid - MOA of LPS: 1. LPS activates macrophages --> release of TNF-α, IL-1 (major mediator for fever), and IL-6 2. Macrophage activation --> cytokines --> tissue damage 3. damage to endothelium from bradykinin-induced vasodilation --> shock 4. coagulation (DIC) is mediate through activation of Hageman factor

Question 27

MOA of LPS:

Answer 27

1. LPS activates macrophages --> release of TNF-α, IL-1 (major mediator for fever), and IL-6 2. Macrophage activation --> cytokines --> tissue damage 3. damage to endothelium from bradykinin-induced vasodilation --> shock 4. coagulation (DIC) is mediate through activation of Hageman factor - pt presents with septic shock and has gram - org on blood culture. What caused the shock symptoms? LPS (specifically, Lipid A portion)

Question 28

Exotoxins

Answer 28

- are protein toxins secreted by bacterial cells (some gram +, some gram -) - can be modified by chemicals/heat to produce a toxoid that is still immunogenic, but no longer toxic so can be used as vaccine - A-B (or 2) component protein toxins: - B component binds to specific cell receptors to facilitate the internalization of A - A component is the active (toxic) component (often an enzyme such as ADP ribosyl transferase) - exotoxins may be subclassed as enterotoxins, neurotoxins, or cytotoxins

Question 29

cytolysins

Answer 29

- lyse cells from OUTSIDE by damaging membrane - ex: C. perfringens alpha toxin = lecithinase - staph aureus alpha toxin inserts itself to form pores in the membrane