Intro to Infectious Disease - Diebel Flashcards
What was Frederick Griffith’s famous experiment? What did it help to establish?
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)
Explain why the gram + bacteria stain purple and gram - stain pink
(+) 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)
Why is catalase an important means of classifying bacteria?
Aerobic bacteria always have catalase because they need it to break down ROS’s.
What is folliculitis and what is a furuncle?
folliculitis - infection of hari follicle
furuncle - develops from folliculitis
Impetigo, what’s that?
Superficial epidermal infection.
Often involves streptococcus
purulent discharge with crusting
highly contagious
What is Erysipelas?
Acute inflammation of dermis involving lymph vessels
Fever, butterfly rash on face
What is cellulitis?
Involves all layers of skin to subcutaneous tissue. Causes fever and leukocytosis. Strep and staphmost common
What causes an abcess?
Its a local collection os purulent material(pus) that is formed by host defenses to wall off the infection
What is gangrene?
Extreme progression of cellulitis. Tissue necrosis and gas in soft tissues
Typical organisms : streptococci, mixed anaerobes, cloistridium
What is necrotizing fasciitis?
Rare and dangerous infection of subcutaneous tissues
Staphylococcus aureus has 3 ways of evading host defenses:
What are they?
Protein A - Binds and stops IgG
Coagulase - forms a fibrin coat around the organism
Hemolysins/Leukocidins - destroy RBC and WBC
What virulence factors does Staph Aureus use for invading deep tissue?
Hyaluronidase - breaks down connective tissue
Staphylokinase - lyses clots the body forms
Lipase - breaks down fat
What toxins can staph aureus produce to create havoc in the host?
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)
How does streptococcus pyogenes present clinically?
localized skin infection (can be impetigo, erysipelas, cellulitis
What are streptococcus pyogenes’ most important virulence factors?
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
Describe Streptococcus’ toxin-related pathology!
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
What are the general clinical presentations of pseudomonas aeruginosa?
Burn wound (cellulitis)
and
Follicultis (hot tub infection)
What is the general progression of clinical lyme disease?
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
Causitive agent of lyme disease?
Borrelia Bergdorferi
Causitive agent of Rocky Mtn Spotted Fever?
Rickettsia Rickettsii
Clinical presentation of rocky mtn spotted fever?
tick bite
maculopaular rash starting in extremities and leading to trunk, fever, headache, renal damage, death
Why is rickettsiia rickettsii an obligate intracellular organism?
Because it needs host ATP to survive
** Could def see a question like this on the test**
