Module 5 Flashcards
Koch’s Postulates
Robert Koch proved bacteria can cause disease.
Koch’s Postulates 4 requirements
1) Microorganism must be found in every case to be called the Causative Agent.
2) Microorganism must be grown in a pure culture
3) Disease must be reproduced when pure culture is injected into healthy host
4) Microorganism must be recoverable from the injected host
Normal Flora
Bacteria normally found on outer surfaces and mucous membranes of the body
Transient Normal Flora
Bacteria different from usual flora and present for short time
Contamination
- Presence of bacteria in/on body site
- Not part of normal flora
- Bacteria not growing
Colonization
Contamination, but bacteria are growing
No host reaction
Infection
Bacteria growing in/on a body site
Causing host reaction
Pathogenicity
Ability of a microorganism to cause disease
Virulence
Degree of pathogenicity
Pathogen
Microorganism capable of causing disease
Nonpathogen
Microorganism not capable of causing disease
Very few microorganisms can be classified this as most are capable of causing some sort of infection
6 Factors contributing to pathogenicity
Capsules Hyaluronidase Collagenase Hemolysins Leukocidins Kinases
Capsules
prevent phagocytes from attaching to bacteria
Hyaluronidase
Extracellular enzyme mainly produced by Gram positive bacteria
Dissolves hyaluronic acid (compound in connective tissue matrix)
Allows bacteria to spread throughout tissue
Collagenase
Breaks down collagen (in connective tissue)
Allows bacteria to spread faster in connective tissue
Hemolysins
Lyse RBCs
Decreases host’s immunity