Module 5: Microbial and Host Interactions Flashcards by Amanda Belick

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

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Define normal flora

Bacteria normally found on outer surfaces and mucous membranes
Fairly consistent with site, but differs from others

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Define transient normal flora

When might it occur?

Bacteria different from normal flora and present for short time
May be from antibiotic use, hospitalization

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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

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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

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Define infection

Bacteria growing in or on body and causing host reaction/infection

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Define pathogenicity

Ability for organism to cause disease

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Define virulence

Degree of pathogenicity

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Define pathogen

Bacteria capable of causing disease

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Define nonpathogen

Not capable of causing disease

Very few, as most can cause disease somewhere to a degree under certain conditions

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List the 6 virulence factors

Capsules
Hyaluronidase
Collagenase
Hemolysins
Leukocidins
Kinases

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How are capsules a virulence factor?

Prevent phagocyte attachment and phagocytosis

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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

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How is collagenase a virulence factor?

Breaks down collagen, allows spread of bacteria in connective tissue

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How is hemolysins a virulence factor?

Lyses red blood cells, decreases host’s immunity

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How are leukocidins a virulence factor?

Kill phagocytic cells

Creates pus

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How are kinases a virulence factor?

Break down fibrin clots formed to isolate infection

Allows bacterial spread

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Define exotoxins

Toxins produced mostly from GPOs that have a specific site of action in the host

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What are exotoxins made of? How do they enter the body?

Mainly protein, are excreted from the bacteria

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How can exotoxins be used in terms of immunization?

They are antigenic and cause immune responses so can be converted to toxoids for immunization

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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

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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