Pathology of infectious diseases

Question 1

Prions

Answer 1

• < 20 nm
• Propagate intracellular
• Infectious agents made entirely up of PrP; this protein is usually found in neurons
• Abnormal protein is resistant to proteases
• Cause of Creutzfeldt-Jakob disease: rapidly progressive dementia; usually sporadic

Question 2

Viruses

Answer 2

• 20-300 nm
• Obligate IC; need a host for replication
• Cause illness in the following ways: a) transient b) latent/persistent (hep B, herpes) c) transformation into malignant form (HPV)

Question 3

Bacteria

Answer 3

• 0.2-13 micrometer

- Possible propagation sites: OI (chlamydia, rickettsia), EC (mycoplasma), FI

Question 4

Fungi

Answer 4

• 2-200 micrometer
• Eukaryotes with thick cell walls
• “Yeast in the heat, mold in the cold”
• Can cause superficial (skin, hair, nails) or deep infections

Question 5

Protozoa

Answer 5

• 1-50 micrometer

- Single-celled eukaryotes

Question 6

Helminths

Answer 6

• Parasitic worms that usually can be seen with the naked eye
• Complex life cycle: sexual reproduction in the definitive host and asexual reproduction in intermediary host/vector

Question 7

Steps in microbial pathogenesis

Answer 7

1. Encounter
2. Attachment to host cells and multiplication
3. Local or general spread in the body
4. Evasion of host defenses
5. Cell and tissue damage
6. Shedding from the body

Question 8

Definition of sepsis

Answer 8

Whole body inflammation due to infection.

Sepsis = SIRS (systemic inflammatory response syndrome) + confirmed infection

Question 9

Criteria for SIRS

Answer 9

• BT <36 or > 38 °C
• HR > 90 bpm
• Tachypnea > 20 bpm or paCO2 < 32 mmHg
• WBC count < 410^9/L or > 1220^9/L

Question 10

Septic shock: definition

Answer 10

Low BP due to sepsis that doesn’t resolve after IV fluid is given.