Pathogenesis

Question 1

Nocardia Pathogenesis

Answer 1

Causes bronchopulmonary disease

Develops after inital colonization of upper respiratory tract by inhalation

Primary cutaneous infections develop from introduction in subcutaneous tissue through trauma

Question 2

M. Tuberculosis Pathogenesis

Answer 2

Intracellular pathogen that established lifelong infection

Enter lower respiratory tract by inhalation

Phagocytized by alveolar macrophages, prevents fusion of phagosome with lysosomes

Macrophage secretes cytokine which increases local inflammation with recruitment of T cells

Granuloma forms with bacteria inside

Alveolar macrophages and Langhans giant cells surround bacteria

Lesion is walled off (tubercle)

Question 3

Tubercle in M. Tuberculosis

Answer 3

Small tubercle (bacteria killed off)

Large/caseous tuburcle (bacteria protected and remains dormant)

Can become reactive later when immune system wanes

Lesion liquefies, bacteria coughed up, may spread to other organs

Question 4

Neisseria Meningitidis Pathogenesis

Answer 4

Inhalation (enter respiratory tract)

Attached to non ciliated columnar cells of nasopharynx (IgA protease assists and pili are key no pili means harder to colonize)

Bacterium internalized in phagocytic vacuole, avoid destruction, replicate and migrate

Exotoxin caused vascular damage

Bacterium enters bloodstream

Travels to meninges and lungs

Question 5

Neisseria Gonorrhoeae Pathogenesis

Answer 5

Sexually passed

Fimbriated cells attach to intact mucus membrane epithelium

Penetration into and multiplication before passing through mucosal epithelial cells

Establish infection

Sites of inoculation (Cervix/Vagina or Urethra/Penis)

Can be passed anally/orally

Question 6

Campylobacter Pathogenesis

Answer 6

Infectious dose and host factors influence development (High does and most bacterium killed by gastric acid/Low does with neutralized gastric acid)

Pathogenesis not clearly defined (No good animal model)
Damage to mucosal surface of jejunum, ileum, colon
Non-motile and adhesion lacking strains are avirulent
Seems to be associated with Guillain-Barre Syndrome

Question 7

Helicobacter pylori

Answer 7

Colonize mucosal lining of stomach and duodenum

Colonization initiated by blockage of acid production by acid inhibitor protein, neutralization of acid by ammonia produced by urease activity

Tissue damage mediate by ureases breaksdown ammonia by-products, Mucinase, Phospholipase, Vaculating cytotoxin

Question 8

Salmonella Pathogenesis

Answer 8

Ingestion of contaminated food

T3SS mediates invasion into M cells

Located in Peyer’s patches (transport foreign particles to macrophages for clearance)

Cells survive phagosome, replicate and spread

Inflammation confined to GI tract

Systemic disease very serious

Question 9

Shigella Pathogenesis

Answer 9

Attach to and invaded M cells in Peyer’s patches via fimbriae and T3SS

Survive phagocytic vacuole and replicate

Invade adjacent cells

Induce apoptosis of cells (leads to sloughing of epithelium/colonic ulcers)