Pathology of Infectious Diseases

Question 1

infection is established if (2 factors)

Answer 1

1. virulence factors overcome normal host defenses
   OR
2. host defenses are compromised

Question 2

infections can get in by various methods, including

Answer 2

-breaching epithelial surfaces
-inhalation
-sexual transmission
-vertical transmission (mother to fetus, birth, postnatal maternal milk)

Question 3

dissemination of pathogens

Answer 3

-may remain at localized site
OR
-spread to other sites via:
*direct extension (following tissues planes of least resistance)
*lymphatics
*bloodstream
*nerves
*tissue tropism (specific tissue involvement/characteristic disease patterns)

Question 4

evasion of defenses by pathogens

Answer 4

-antigenic variation (looking different to the immune system: expressing different surface antigens, etc)
-avoiding phagocytosis (capsule, protein A, etc)
-inactivation of complement
-suppressing adaptive immunity
-latency phase genes

Question 5

damage mechanisms of pathogens

Answer 5

1. direct cytotoxicity (infect a cell and kill it or transform it)
2. indirect cytotoxicity (release toxins, killing distant cells)
3. collateral cytotoxicity (induce host immune responses, causing tissue damage)

Question 6

endotoxins

Answer 6

LPS in outer membrane of gram - organisms stimulates host immune responses and injury

Question 7

exotoxins

Answer 7

secreted bacterial proteins that cause cellular injury and disease

Question 8

spectrum of inflammatory responses to infection

Answer 8

1. suppurative acute inflammation
2. non-suppurative inflammation
3. granulomatous inflammation
4. cytopathic / cytoproliferative change
5. necrotizing inflammation
6. chronic inflammation

Question 9

suppurative acute inflammation

Answer 9

neutrophilic infiltration
*response to acute infection from extracellular bacteria
*results in formation of EXUDATE (pus = neutrophils + liquefactive necrosis)

Question 10

non-suppurative inflammation

Answer 10

**NON-neutrophilic infiltrates (eosinophils, lymphocytes, monocytes, etc)
*response to acute infections from viruses, intracellular bacteria, or parasites

Question 11

granulomatous inflammation

Answer 11

*defined aggregates of macrophages, some combining into multi-nucleated giant cells
*T-cell mediated immune response
*response to SLOWLY DIVIDING organisms (mycobacteria, fungi)

Question 12

cytopathic / cytoproliferative change

Answer 12

*virus-mediated cellular damage
*ABSENT host inflammatory response
1. polykaryons (cells induced to fuse, forming a blister)
2. inclusion bodies (visible viral replication within cell)
3. neoplastic cellular proliferation (b/c of oncogene expression)

Question 13

necrotizing inflammation

Answer 13

*toxin-mediated severe tissue damage and cell death
*typically only few inflammatory cells involved
-viruses may cause necrotic inflammation when host cell damage is widespread and severe

Question 14

what are the most relevant pathogens for necrotizing inflammation

Answer 14

*Clostridium perfringens
*group A strep

Question 15

chronic inflammation / scarring

Answer 15

*lymphocytes/plasma cells with associated fibrosis
*final common pathway of many infections
*progressive shift in cell type at site of inflammation
*simultaneous destruction and healing

Question 16

exit strategies for pathogens

Answer 16

release from body for transmission to other individuals:
-person to person (direct contact)
-respiratory aerosolization
-direct ingestion
-fecal-oral
-parenteral direct inoculation
-sexual
-childbirth
-zoonotic exposures

Question 17

gold standard for identifying pathogens in lab

Answer 17

culture (from a biopsy/tissue)