7/30/2019 (12) Pathogenesis of Infectious Disease

1/2

Pathogenesis of Infectious Disease

Prepared by Dr. Jhason John J. Cabigon

1. Definition of Terms

a. Pathogen a microorganism capable of causing disease

b. Pathology the study of the structural and functional manifestations ofdisease

c. Pathogenicity the ability to cause disease

d. Pathogenesis the steps or mechanisms involved in the development of adisease

2. Infection

a. Infection colonization by a pathogen

b. Infectious disease when the pathogen goes on to cause disease3. Why Infection Does Not Always Occur

a. The microbe may land at an anatomic site where it is unable to multiply

b. Non-attachment to specific receptor sites

c. Antibacterial factorsd. Indigenous microflora

e. Influence of individuals nutritional and overall health statusf. Immunity to certain pathogens

g. Phagocytic White Blood Cells

4. Course of an Infectious Diseasea. Exposure to Pathogen

b. Incubation period

c. Prodromal period

d. Period of Illnesse. Convalescence, Disability or Death

5. Signs and Symptomsa. Symptom evidence of disease that is experienced or perceived by thepatient; subjective complaint

b. Sign objective evidence of a disease

6. Classification of Diseasea. Localized vs Systemic Infection

b. Primary vs Secondary Infection

c. Latent Infections

d. Acute, Subacute and Chronic Diseases7. Steps in the Pathogenesis of Infectious Diseases

a. Entry of the Pathogen

b. Attachment of Pathogenc. Multiplication

d. Invasion/Spread

e. Evasion of Host defensesf. Damage to Host tissues

8. Virulence the measure of pathogenicity

* Virulence Factors physical attributes of pathogens that enable them to

escape various host defense mechanisms and cause disease

7/30/2019 (12) Pathogenesis of Infectious Disease

2/2

a. Bacterial Structures

1. Adhesin and Ligand attaches to receptors and integrins2. Bacterial Fimbriae (Pili) long, thin, hairlike, flexible projections

composed of primarily of an array of proteins called pilin

3. Flagella enable bacteria to gain access to anatomical areas thatnonmotile bacteria cannot reach

4. Capsules serve as antiphagocytic function

b. Enzymes1. Coagulase enables bacteria to produce clots within which they hide

2. Kinases enable bacteria to dissolve clots

3. Hyaluronidase spreading factor; dissolves hyaluronic acid, enabling

bacteria to penetrate deeper into tissues4. Lecithinase destroys cell membrane

5. Necrotizing enzymes cause massive destruction of tissues

c. Toxins

1. Endotoxin released from the cell walls of Gram negative bacteria;causes fever and septic shock

2. Exotoxinsa. Neurotoxins cause damage to central nervous system;

tetanospasmin and botulinal toxins are examples

b. Enterotoxins cause gastrointestinal diseasec. Miscellaneous exotoxins

c.1. Clostridium difficile toxin B causes

pseudomembranous colitis

c.2. Staphylococcus aureus TSST-1 causes Toxic ShockSyndrome

c.3. Exfoliative toxin produced by Staphylococcus

aureus; causes Scalded Skin Syndromec.4. Erythrogenic toxin produced by Streptococcus

pyogenes; causes Scarlet Fever

c.5. Diptheria toxin produced by Corynebacteriumdiptheriae; causes Diptheria

c.6. Leukocidins cause destruction of leukocytes

9. Mechanisms by Which Pathogens Escape Immune Response

a. Antigenic Variationb. Camouflage and Molecular Mimicry

c. Destruction of Antibodies