Infection, Infectious Disease, And Epidemiology 100 Exam 3

Front 1

virulence

Back 1

the ability of a microorganism to cause disease

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virulence factor

Back 2

substance that a microorganism produces that increases its ability to infect a host or to cause damage to the host

most are proteins but there are some exceptions

2 categories: invasins, toxins

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Invasins

Back 3

help microorganisms enter a host or evade the host's defenses

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toxins

Back 4

poisons or enzymes that damage the host

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examples of bacterial virulence factors

Back 5

flagella

capsules

adhesions

extracellular enzymes

toxins

antiphagocytic chemicals

fimgrae or pili

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flagella

Back 6

allow bacteria to move

motility helps the bacteria to spread and this is important in some infections

examples: E. coli and Proteus vulgaris are the 2 leading causes of urinary tract infections and both are motile by means of flagella

bacteria in the urinary tract tend to be washed out by the flow of urine

if the bacteria are able to move up the urethra, they are able to resist being flushed out

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capsules

Back 7

slimy layer of capsular polysaccharides protects bacteria from phagocytosis by masking surface antigens and reducing the attachment to antibodies

capsules also help the bacteria stick to the surfaces and to form a biofilm

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adhesions

Back 8

protein that is found on the surface of bacterium that helps it to stick to something

some help bacteria stick to specific sites on the surface of a host cell

bacteria that invade the gastrointestinal tract often have well developed adhesions that allow them to avoid being flushed away

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extracellular enzymes

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break down parts of the host's defenses and body structures

allow the bacteria to penetrate deeper into the host's tissues or it can free up nutrients that the bacteria can utilize to grow

example: Helicobacter pylorie excretes mucinase, degrades mucous in the stomach and allows the bacteria to penetrate to the tissues of the stomach wall where they cause ulcers

Front 10

toxins

Back 10

poison that is produced by a microorganism

may harm tissues or trigger a pathogenic immune response

examples: cholera toxin made by Vibrio cholera causes severe diarrhea; enterotoxin made by Staphylococcus aureus causes diarrhea and vommitting; tissue necrosis factor made by Clostridium perfringens causes cell death in gangrene

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antiphagocytic chemicals

Back 11

leukocidins are exotoxins that kill white blood cells (leukocytes) this is very bad because the WBCs help fight the infection

Front 12

fimbrae or pili

Back 12

hair-like projections that help bacteria to stick to each other and other surfaces

sometimes fimbrae ahve adhesion proteins as a part of their structure

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Bacterial Exotoxins

Back 13

excreted by the bacterium

most are proteins and ezymes

tend to target specific functions in the host

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bacterial endotoxins

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part of the bacterial cell or cell wall that elicits an inflammatory response in the host

released by growing bacterial cells as the debris of cell division or by bacterial cells that are decomposing

tend to have a more general or systemic mode of action

lipopolysaccharide (lps) from the outer membrane of gram positive bacteria is the most commom endotoxin

lps is a non-specific activator of the inflammatory response and a pyrogen (causes fever)

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Diptheria toxin

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exotoxin

A-B type toxin

excreted by Corynebacterium diphtheria when it infects the throat

enters the host cell and acts as an enzyme that inactivates the host cell's ribosomes

b/c it is an enzyme, one molecule of toxin inactivates thousands of ribosomes, killing the host cell by shutting down its protein synthesis

bacteria rarely enters the host beyond an infection of the throat, but it can travel in the blood and kill cells that are far away from the throat

if too many muscle cells i the heart are killed by the toxin, the patient dies

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botulism toxin

Back 16

exotoxin

excreted by Clostridium botulinum and is neurotoxin that causes flaccid paralysis (muscle relax)

flaccid paralysis of the heart and lungs can be fatal

in food poisoning cases the bacteria produce the toxin while growing anaerobically in canned food

ingestion of toxin causes disease without infection

A-B type toxin

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Tetanus toxin

Back 17

exotoxin

excreted by Clostridium tetani

neurotoxin that causes a rigid paralysis (muscle spasms)

kills the victim by exhaustion from the constant muscle contraction

produced by the bacteria when they infect a wound

A-B type toxin

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Streptococcus pyogenes hemolysin

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exotoxin

enzyme that damages the cell membranes and can cause red blood cells to rupture

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Staphylococcus aureus enterotoxin

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heat stable

causes severe nausea and diarrhea

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Vibrio cholera toxin

Back 20

causes severe diarrhea

gene for the toxin is encoded on a lysogenic bacteriophage

strains of Vibrio cholera that don't have the phage, don't make toxin and don't cause disease

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epidemiology

Back 21

study of the interactions btw disease causing pathogenic microorganisms and society

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epidemic

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sudden increase in the number of cases of a disease that are seen in the population

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tools of epidemiologist include

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statistics

maps and charts

public health measures

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statistics

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prevalence: total # of cases/population

describes the health of a population in regarde to disease

incidence: # new cases/population

describes the rate of change in the number of cases

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prevalence

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always a higher number than incidence because the total number of cases includes all new cases as well as old cases

for acute disease with short duration, prevalence is closer to incidence and a decline in incidence is quickly followed by a decline in prevalence

for chronic illness w/ a long duration, prevalence may be substantially higher than incidence and a decline in incidence is not followed by a quick decline in prevalence

incidence is a more predictive tool

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endemic disease

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the number of cases of the disease is relatively stable and predictable in the affected area

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epidemic disease

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there is a sudden and unpredicted increase in the number of cases of the disease in a region

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sporadic disease

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the occurrence of the disease is very rare and unpredictable

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pandemic disease

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there is an epidemic that occurrs in many regions of the world simultaneously

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public health measures

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mandatory disease reporting

quarantine--isolation of persons with an infections illness

enforcement of hygiene standards, esp in public eating places

laws regarding clean water and sewage treatment

mandatory immunization--school enrollment requirements

in home assistance to persons with communicable diseases -- TB officer