Objective 3: Describe the mechanism of bacteria-induced injury

Question 1

Bacterial Virulence

Answer 1

depends on ability of bacteria to adhere, invade, and deliver toxic moieties

Question 2

Bacterial ADHERENCE**

Answer 2

BACTERIA MUST ATTACH TO CAUSE INFECTION.

a. Adhesins are bacterial surface molecules that bind to host cells
- lipoteichoic acids, M proteins of S. pyogenes
- fimbriae or pili on surface of gram negative bacteria
b. Entry into Macrophages-directed by receptors that recognize antibodies or complement on the surface of bacteria (survive phagocytosis)
c. Entry into epithelial cells-dependent on interactions between bacterial surface and epithelial cell receptor such as integrins (only human flu strains can attach to our receptors).

Question 3

Molecules on the surface of gram negative bacteria involved in pathogenesis

Answer 3

• adherence protein
• pilus
• non-pili adhesins

Question 4

Molecules on the surface of gram-POSITIVE bacteria involved in pathogenesis

Answer 4

• Protein F
• Fibrila (M protein)
• Lipotechoic acid

(all embedded in the thick peptidoglycan wall)

Question 5

Bacterial ENDOtoxin

Answer 5

• very immunogenic, ONLY gram NEGATIVE
• lipopolysachharide (LPS): structural component of outer cell wall in gram negative bacteria; induces host cytokine release to cause fever, activate macrophages & B cells

Question 6

Bacterial EXOtoxin

Answer 6

• excreted by gram POSITIVE and gram NEGATIVE
• toxins released by bacteria that interfere with cellular metabolisn and allow bacteria to outgrow competing bacteria (Ex: Diphtheria toxin, Vibrio cholera toxin, anthrax toxin)