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
Leukocidins
Kills phagocytic cells creating pus
Kinases
Break down fibrin clot (formed by body to isolate infection)
Bacteria break through clot and spread
2 types of bacterial toxins
exotoxins and endotoxins
Exotoxins
Mainly produced by Gram Positive bacteria
Excreted from living bacterial cells
Mainly protein molecules
Antigenic (causes an immune response)
May be converted to toxoids for immunization
Have a specific site of action in host
Endotoxins
Produced my Gram Negative bacteria
Part of the cell wall (Lipopolysaccharide of outter membrane)
Released when cell walls are lysed (from antibiotics)
Do not form toxoids for immunization
Nonspecific sites of action in the host
Symptoms: aches, malaise, fever, decreased blood pressure, shock
Signs of bacterial infection
Fever, lymph node swelling, inflammation, exudate, Granulomatous infection, cellulitis`
Lymph Node Swelling
System accumulates and drains waste fluids
Nodes may become infected/swollen due to increase of antibody-producing cells
Neck, under arms, groin
Inflammation
Damaged cells release histamine
Results in dilation of blood vessels, fluid and phagocytes move in
Exudate
Accumulation of fluid at site of infection
Purulent exudate, serous exudate, transudate
Purulent exudate
AKA Polymorphonuclear neutrophils (PMNs)
Many WBC, neutrophils, pus
Serous exudate
Watery fluid is few polymorphonuclear neutrophils (PMNs) and less protein
Transudate
noncellular fluid (leadage from blood or lymph vessels)
Granulomatous Infection
Granuloma formed at site of infection
Collections of macrophages
-results in increased capacity for phagocytosis and digestion
Epidemic
Many people in an area having a disease over a short period of time
Endemic
Disease constantly present in a small percentage of the population
Pandemic
World-wide epidemic
Epidemiology
the study of when/where disease occurs and how it is spread
Endogenous Infection
Infecting bacteria come from the host’s own body
Exogenous Infection
Infecting bacteria come from outside the hosts body
Nosocomial Infection
Hospital acquired infection
Carrier
Potential pathogen carried by a host (no signs of infection)
Primary Infection
Initial infection caused by a microorganism
Secondary Infection
Infection following a primary infection caused by a different microorganism
Nonspecific infection
Microbial cause not identified
Opportunistic Infection
Caused by Low Grade Pathogen
typically in patients with lowered immune system
Disseminated Infection
Spread to most parts of the body
