Module 5: Microbial and Host Interactions Flashcards
What are Koch’s postulates? (4)
- Microorganism must be found in every case of disease to be the CAUSATIVE AGENT
- Microorganism must be isolated from host and grown in a PURE CULTURE
- Disease must be REPRODUCED when pure culture is injected in healthy individuals
- Microorganism must be RECOVERABLE from injected host
Define normal flora
Bacteria normally found on outer surfaces and mucous membranes
Fairly consistent with site, but differs from others
Define transient normal flora
When might it occur?
Bacteria different from normal flora and present for short time
May be from antibiotic use, hospitalization
Define contamination
When might it occur?
Bacteria not part of normal flora present on body site but not actually growing, NO INFECTION
ex: fecal contamination
Define colonization
When might it occur?
Bacteria not part of normal flora present on body site and growing, NO HOST REACTION, NO INFECTION
ex: gram negative rods growing in the throat
Define infection
Bacteria growing in or on body and causing host reaction/infection
Define pathogenicity
Ability for organism to cause disease
Define virulence
Degree of pathogenicity
Define pathogen
Bacteria capable of causing disease
Define nonpathogen
Not capable of causing disease
Very few, as most can cause disease somewhere to a degree under certain conditions
List the 6 virulence factors
- Capsules
- Hyaluronidase
- Collagenase
- Hemolysins
- Leukocidins
- Kinases
How are capsules a virulence factor?
Prevent phagocyte attachment and phagocytosis
What is hyaluronidase? How is it a virulence factor?
Extracellular enzyme produced by gram positives
Dissolves hyaluronic acid (in connective tissue) allowing bacteria to spread
How is collagenase a virulence factor?
Breaks down collagen, allows spread of bacteria in connective tissue
How is hemolysins a virulence factor?
Lyses red blood cells, decreases host’s immunity
How are leukocidins a virulence factor?
Kill phagocytic cells
Creates pus
How are kinases a virulence factor?
Break down fibrin clots formed to isolate infection
Allows bacterial spread
Define exotoxins
Toxins produced mostly from GPOs that have a specific site of action in the host
What are exotoxins made of? How do they enter the body?
Mainly protein, are excreted from the bacteria
How can exotoxins be used in terms of immunization?
They are antigenic and cause immune responses so can be converted to toxoids for immunization
Give examples of exotoxins (3)
Clostridium botulinum - Botulism toxin acts on neuron and muscle cell junction
Clostridium tetani - Tetanus toxin excites the CNS causing muscle spasms
Staphylococcal enterotoxin - affects intestine causing diarrhea
Define enodotoxins
Toxins produced by gram negative bacteria that do not have a specific site of action in the host
Cause aches, malaise, fever, drop in blood pressure, shock
What are endotoxins made of? How do they enter the body?
They are lipopolysaccharides that are part of the cell wall, are released when the cell is lysed by antibioticsq
Give an example of an endotoxin
Salmonella endotoxin
List 6 signs of bacterial infection
Fever, swollen lymph nodes, inflammation, exudate, granulomatous infection, cellulitis
Why do lymph nodes swell in infection?
May be infected or just getting larger due to proliferation of antibody-producing cells
Why is inflammation a sign of infection?
Damaged cells release histamine which dilates blood vessels so fluid and phagocytes move in
What are 3 kinds of exudate? What does each entail?
Purulent - WBC’s/pus
Serous - watery fluid, few WBC’s, less protein
Transudate - noncellular fluid, leakage from blood or lymph vessels
What is granulomatous infection? What causes it?
Granuloma at the site of infection, collection of activated macrophages
What is the purpose of a granuloma?
To increased phagocytosis and form a “wall” around the infection to prevent spreading
What is cellulitis?
Diffuse purulent inflammation, fluid spreads between tissue layers causing swelling and redness
Define epidemic
Many people in one area have disease over a short time
Define endemic
Constantly persistent in small percentage of population
Define pandemic
Epidemic occurring worldwide
Define epidemiology
Study of when/where diseases occur and their spread
Define endogenous infection
Infecting bacteria come from the host
Define exogenous infection
Infecting bacteria come from an outside source
Define nosocomial infection
Infection result of being in the hospital
Define carrier
Potential pathogen is carried by the host without any signs of infection
Define primary infection
Initial infection
Define secondary infection
Second infection cause by a different organism than the first
Define nonspecific infection
Microbial cause not identified
Define opportunistic infection
Caused by low grade pathogen usually in patient with lowered defences
Define acute infection
Short lasting
Define chronic infection
Low grade, long lasting
Define localized infection
Infection restricted to small area
Define disseminated infection
Infection spread to most of the body
Almost all humans have Streptococcus viridans growing in the mucous membranes of their upper respiratory tract at all times with no adverse host reaction. This would be called
a. normal flora
b. contamination
c. colonization
d. infection
a. normal flora
When a person eats some food containing gram negative rods resulting in these bacteria being present without actually growing in the mouth, this is called
a. normal flora
b. contamination
c. colonization
d. infection
b. contamination
When gram negative rods are eaten and start growing in the upper respiratory tract but do not cause any host reaction, it is called
a. normal flora
b. contamination
c. colonization
d. infection
c. colonization
When gram negative rods that are eaten cause exudate and fever it is called
a. normal flora
b. contamination
c. colonization
d. infection
d. infection
Enzymes produced by bacteria resulting in dissolution of clot are called
a. hyaluronidase
b. collagenase
c. leukocidin
d. kinase
d. kinase
Which of the following is not true of bacterial exotoxins?
a. part of the gram negative cell wall
b. heat labile proteins
c. converted to toxoids for immunization
d. act of specific host tissue
a. part of the gram negative cell wall
An exudate containing protein and many polymorphonuclear neutrophils (PMN’s) is called
a. serous
b. transudate
c. purulent
c. purulent
