Microbiology: Virulence Factors

Chapter 3

Microbial Diseases

Jenna Lee Q. Valencia, RPh, BSCPS

Department of Pharmacy

School on Natural Sciences

Saint Louis University

Microbial DiseasesPathogenicity

Virulence

A. VIRULENCE

FACTORS

1. Adhesion FactorsSpecialized structures or

proteinsEnables microorganisms to

attach themselves to proteins

Ligand

2. Extracellular EnzymesMany pathogens secrete

enzymes that enable them to: Dissolve structural chemicals in the

body Maintain an infection Invade further Avoid body defenses.

a. Hyaluronidase“Spreading Factor”Digests hyaluronic acid

b. CollagenaseBreaks down collagen

c. CoagulaseCoagulates blood proteinsProviding a “hiding place” for

bacteria within a clot.

d. KinasesSuch as staphylokinase and

streptokinase Digests blood clots

e. Ig A ProteasesSplit Ig A at specific bondsInactivates Ab activity

f. NeuraminidaseProduced by intestinal

pathogensDegrades neuraminic acid

3. ToxinsChemicals produced by

pathogens that either harm tissues or trigger host immune responses that cause damage.

3. ToxinsTwo types of Toxins:

a. Exotoxin b. Endotoxin

a. ExotoxinsA-B Toxins

Cytotoxins

ExotoxinsNeurotoxin

Enterotoxin

Superantigens

Examples of Exotoxins

Diphtheria ToxinCorynebacterium

diphtheriae

Inhibits protein synthesis in eukaryotic cells

Erythrogenic ToxinsSuperantigens Damage the

plasma membranes of blood capillaries

Botulinum ToxinClostridium

botulinumA-B neurotoxininhibits the

release of acetylcholine

Tetanus ToxinClostridium

tetaniAKA:

TetanospasminA-B Neurotoxin

Vibrio EnterotoxinVibrio

choleraeAKA: Cholera

toxinA-B

enterotoxin

b. EndotoxinsGram negative bacteriaLipid portion of the outer

membraneAKA: Lipid A

4. Antiphagocytic Factors

CapsulesAntiphagocytic Chemicals

CapsulesComposed of chemicals that

are normally found in the body

Slippery

Antiphagocytic Chemicals

Chemicals that prevent the fusion of lysosomes with phagocytic vesicles