Intro to Infectious Disease - Diebel

Question 1

What was Frederick Griffith’s famous experiment? What did it help to establish?

Answer 1

Experiment with bacteria and mice that showed that DNA was in fact the heritable genetic material.

Also showed that this genetic material could be transferred between viruses (virulence factors)

Question 2

Explain why the gram + bacteria stain purple and gram - stain pink

Answer 2

(+) have a very thick wall of proteoglycan that holds in the crystal violet stain once iodine is added

(-) does NOT, so when alcohol is used as an organic solvent, the crystal violet leaves

Afterwards they are both stained with safranin (pink)

Question 3

Why is catalase an important means of classifying bacteria?

Answer 3

Aerobic bacteria always have catalase because they need it to break down ROS’s.

Question 4

What is folliculitis and what is a furuncle?

Answer 4

folliculitis - infection of hari follicle

furuncle - develops from folliculitis

Question 5

Impetigo, what’s that?

Answer 5

Superficial epidermal infection.
Often involves streptococcus
purulent discharge with crusting
highly contagious

Question 6

What is Erysipelas?

Answer 6

Acute inflammation of dermis involving lymph vessels

Fever, butterfly rash on face

Question 7

What is cellulitis?

Answer 7

Involves all layers of skin to subcutaneous tissue. Causes fever and leukocytosis. Strep and staphmost common

Question 8

What causes an abcess?

Answer 8

Its a local collection os purulent material(pus) that is formed by host defenses to wall off the infection

Question 9

What is gangrene?

Answer 9

Extreme progression of cellulitis. Tissue necrosis and gas in soft tissues

Typical organisms : streptococci, mixed anaerobes, cloistridium

Question 10

What is necrotizing fasciitis?

Answer 10

Rare and dangerous infection of subcutaneous tissues

Question 11

Staphylococcus aureus has 3 ways of evading host defenses:

What are they?

Answer 11

Protein A - Binds and stops IgG
Coagulase - forms a fibrin coat around the organism
Hemolysins/Leukocidins - destroy RBC and WBC

Question 12

What virulence factors does Staph Aureus use for invading deep tissue?

Answer 12

Hyaluronidase - breaks down connective tissue
Staphylokinase - lyses clots the body forms
Lipase - breaks down fat

Question 13

What toxins can staph aureus produce to create havoc in the host?

Answer 13

Toxic shock syndrome: Produces TSST, a superantigen that promotes release of IL-1 and TNF (acute fever, rash, hypotensive shock, organ dysfunction, death)

Scalded Skin Syndrome: ET-A and ET-B diffuse (skin sloughs off, fluid loss, 2ndary infection, death, affects kids most often)

Question 14

How does streptococcus pyogenes present clinically?

Answer 14

localized skin infection (can be impetigo, erysipelas, cellulitis

Question 15

What are streptococcus pyogenes’ most important virulence factors?

Answer 15

Strptokinase - converts plasminogen to plasmin
M-protein - resists phagocytosis
Hyaluronidase - breaks down connective tissue
DNAse - digests DNA
Streptolysin O - destroys RBC
Steptolysin S - destroys WBC

Question 16

Describe Streptococcus’ toxin-related pathology!

Answer 16

Toxic Shock - Cellulitis leads to release of pyrogenic exotoxin A (superantigen), causes fever, shock, organ failure

Necrotizing Fasciitis - Deep infection from trauma, releases exotoxin B, a protease whch creates rapid necrosis in the fascia

Question 17

What are the general clinical presentations of pseudomonas aeruginosa?

Answer 17

Burn wound (cellulitis)
and
Follicultis (hot tub infection)

Question 18

What is the general progression of clinical lyme disease?

Answer 18

Stage 1 (first 10 days) Erythema chronicum migrans
Stage 2 (2 weeks)
CNS issues - aseptic menigitis, peripheral neuropathy
CV - carditis, AV nodal block
Skin - secondary anular lesions
Joints - migratory myalgias, arthritis
Stage 3 (months to years)
chronic arthritis, encephalopathy, acrodermatitis chronicum atrophicans

Question 19

Causitive agent of lyme disease?

Answer 19

Borrelia Bergdorferi

Question 20

Causitive agent of Rocky Mtn Spotted Fever?

Answer 20

Rickettsia Rickettsii

Question 21

Clinical presentation of rocky mtn spotted fever?

Answer 21

tick bite

maculopaular rash starting in extremities and leading to trunk, fever, headache, renal damage, death

Question 22

Why is rickettsiia rickettsii an obligate intracellular organism?

Answer 22

Because it needs host ATP to survive

** Could def see a question like this on the test**