Activities of pathogens 2

Question 1

Virulence factors
-define
-examples of factors

Answer 1

Genetic determinents that allow a pathogen to cause disease:
Adherence
Invasion
Immune evasion
Toxins

Question 2

Define virulence
-define

Answer 2

The capacity to cause disease in hosts with intact defences
-requires some breach of host defences

Question 3

Bacteria and disease:
- pyogenic infection
-granulomatous/chronic infection
-Intoxication (change in host physiology and tissue destruction)
- immune mediation

Answer 3

• pyogenic infection
  Tissue invasion, mulptlication and immune response in sterile site. Eg N.meningitidis enters the CSF and provokes innate immunity (phagocytes) causing meningitis

-granulomatous/chronic infection
Evade immune system, cellular immunity required. Activated macrophages fuse and surround the Ag: Incomplete host response = granumola. Eg Mycobacterium

-Intoxication (change in host physiology - vibrio cholerae toxin
and tissue destruction- clostridium perfringens

• immune mediation
  Antigen mimicry (steptococcus pyogenes)

Cancer
- stomach cancer caused by H plyori

Question 4

Effects of Cholera infection

Answer 4

1. Often from unsanitary water supply profuse watery diarrohea
2. Cl, Na, water is lost in the bowel lumen causing profuse diarrhoea
3. cGMP builds up inside the cell and causes the pump on the cell membrane to pump CL ions out of cell
4. Cholera toxin inhibits GIPase enzyme
5. Cholera divides in bowel and releases a toxin

Question 5

Process of appendicitis

Answer 5

1. Bacteria interact with the cells lining the appendix
2. Bacteria damage the cells using toxins/cytolysins
3. Damaged cells release cytokines that trigger inflammation
4. neutrophils leave BV and travel to site of infection (chemotaxis)
5. Phagocytose bacteria
6. Toxin granules fuse with the phagosome to form lyosome

7.bacteria are killed withi the lyosome (hydrogen perioxide)

Inflammed appendix has a lot of immune cells, bacteria and dead bacteria causing PAIN. Nerves from appendix enter the spinal cord at the level of the umbilicus so the initial pain is felt there. In time the inflamm spreads to partietal peritoneum so pain shifts to the right iliac fossa

Question 6

Outcome of appendicitis (internal)

Answer 6

1. Inflammed appendix is encased by omentum and forms a chronic inflam appendicial mass.
2. Appendix can rupture causing peritonitis, sepsis and death

Question 7

Appendicitis management
- why arent antibiotics given now

Answer 7

Diagnosis
Pain relief
Fluids
Surgery
Antibiotics

• risk of reinfection if not removed and antibiotics given

Question 8

Streptococcus pyogens
-causes
-symptoms

Answer 8

Common cause of pharyngitis (sometimes leading to rheumatic fever) and skin infection

Fever
painful joints
Inflamm of connective tissue and muscle in heart
rash

Question 9

Steps in S.pyogenes infection

Answer 9

1. Innate immune system activation and S pyogenes toxins damage cells in pharynx
2. Inflamm of pharynx
3. Pain, erythema, swelling, purulent exudate
4. Bacteria has surface proteins that it uses to bind to cells of pharynx (M proteins) which bind to factor H to destroy C3 convertase
5. Ab form against M proteins and sometimes bind to human tissue
6. If bind to human tissue then cause inflammation leading to rheumatic fever

Question 10

Cause of appendix

Answer 10

Mostly E.coli feed off carbon etc in the appendix but when this runs lows, they begin to damage the appendix epithelial cells to get access to more resources. This causes massive cytokine release = inflammation

Question 11

sensation of pain movement

Answer 11

starts at the belly button and migrates to lower right quadrant due to the inflammation and thus pain migrating to partieal perneum