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76 Cards in this Set

  • Front
  • Back
What is the definition of a PATHOGENIC bacteria?
One that is capable of causing disease in a normal host.
What is required in order to prevent and treat pathogenic bacterial infection?
Vaccines and antimicrobials
What does the term Virulence refer to?
The degree of pathogenicity
What is an organism that is NOT associated with disease called?
What is the term for an organism that lives in relationship with a host in a way that both are benefited by the association?
What is the term for an organism that causes disease in a compromised host?
Opportunistic pathogen
What is a common saprophyte?
Bacillus species
What is a common commensal?
What are the 2 most common opportunistic pathogens?
What bacteria have the potential to become opportunistic pathogens?
Commensials - normal flora
What are 2 important factors that determine the outcome of a bacterial infection?
-Dose of infection
-Incubation period
What is especially dangerous about an incubation period?
The individual is highly contagious but asymptomatic
1. Finds correct portal of entry
2. Attaches and colonizes
3. Resists host defense
4. Damages the host
What is necessary for a pathogenic bacterium to successfully colonize the host?
It must attach to specific host tissue.
What 2 components of the host defense mechanism must the pathogen resist?
-Nonspecific TLR/cytokine and macrophages
-Specific cell mediated T/B cells
What are the 2 main Mechanisms of Pathogenicity in microbes?
1. Invasiveness
2. Toxigenicity
What is invasiveness?
The ability to grow in the host
What is toxigenicity?
The ability to produce toxins
What are 2 key points about inoculum that influence the virulence of a pathogen?
-Portal of entry
-Normal flora
How does portal of entry affect the virulence of Salmonella infection?
Inoculating by subcutaneous route results in a 200X more toxic infection than orally.
How does normal flora affect the virulence of a pathogen?
When mice are pretreated with Streptomycin and then given Salmonella orally, it is 30,000X more virulent bc of decreased normal gut flora.
So why does oral inoculation result in a less virulent infection than subcutaneous? (2 reasons)
-Stomach is acidic and Salmonella can't survive it
-Gut normal flora prevent colonization
When a microbe enters a host, what causes DAMAGE to the host?
-Invasiveness - growth
What about a Noninvasive microbe is pathogenic to the host?
As opposed to the localized damage caused by invasiveness, where does tissue damage from toxigenicity usually manifest?
At sites distant from the portal of entry.
What is one pathogenic microbe that causes localized infection but distant toxigenicity?
Corynebacterium diphtheriae
-Localized infection in trachea
-Toxin damages all major organs
What do we call the toxins that are produced by pathogenic microbes?
What types of bacteria produce exotoxins?
Both gram pos and neg
What produces endotoxin?
Only gram neg
Which is heat labile?
Exotoxins (they're protein)
How are exotoxins immunogenic? (two ways)
1. They can be neutralized by antibodies
2. They can elicit immune responses when given as a vaccine.
How are exotoxins converted into vaccines?
By denaturing with formalin to convert them into toxoids.
What is NOT a component of toxogenicity of exotoxins?
How much exotoxin is required to be toxic?
Small amounts can do it - like micrograms!
What are the 4 classes of bacterial toxins?
1. Surface acting
2. Pore forming
4. A/B toxins
4. type III and IV secretion
How do Surface acting toxins work?
By binding a cell surface receptor and transducing a signal to the host cell interior.
What is an example of a surface acting toxin?
How do Poreforming toxins work?
By adhering to the cell surface and polymerizing to form a pore, thru which nutrients then efflux.
How do A/B toxins work?
By binding a specific receptor to the Bdomain, being endocytosed, then delivering the catalytic A subunit to the host cell interior which damages it.
How do type III and IV secretion mechanisms work?
The bacterium itself has a little syringe on it that injects toxin into the host cell.
Are bacterial toxins nonspecific?
NO; they are unique and yield specific pathologies.
What are 5 types of covalent modification to host macromolecules?
How are toxins typically formed?
Why do bacteria secrete toxins in a protoxin form?
Because it is stable to the environment.
What are 4 methods of activating protoxins?
What are the resulting molecules from diphtheria protoxin activation?
Proteins A and B
What is the A fragment?
The catalytic component
What is the B fragment?
The binding component
What toxin family is the Diphtheria toxin a member of?
the ADP-ribosylating exotoxin family
What is the structure of the diphtheria toxin?
A + B
What is the gene location of the diphtheria toxin?
Lysogenic phage
What is the mechanism of action of Diphtheria toxin?
ADP-ribosylation and activation of elongation factor 2 (EF2)
What does Diphtheria toxin adp-ribosylation of EF2 result in for the host cell?
Inhibition of protein synthesis
How many cases of Diphtheria were there yearly in the US before the vaccine? After?
Before: 176,000
After: about 1
Where is diphtheria still a major killer of children?
In underdeveloped countries
How much diphtheria toxin is required to be lethal to a nonimmunized person?
A few micrograms
What is the diphtheria vaccine?
Formalin inactivated diphtheria toxin (a toxoid)
Why is the diphtheria toxoid especially useful?
It can be used as a conjugate vaccine when attached to H. flu type B
What is the gene encoding diphtheria toxin encoded within?
A beta phage
What are two types of strains of Corynebacterium diphtheriae?
-Nonlysogenic strains
-Lysogenic strains
What type of infection do NONlysogenic strains of C. diphtheriae produce?
LOCALIZED in the upper resp tract - pseudomembrane
What type of bacterial growth is seen in nonlysogenic C. diphth infections?
What type of growth is seen in Lysogenic strains of C. diphtheriae infections?
Also localized, noninvasive, but with systemic pathology due to the toxins.
In what 4 organs is pathology seen due to lysogenic C. diphtheria toxins?
-Nervous system
What is death caused by C. diphtheriae due to?
Cardiac failure
How many domains does the diphtheria toxin have? What are they?
B- Receptor binding
-Translocation domain
Once the B-receptor domain binds to a cell surface, how does the diphteria toxin get into the host cell?
What happens within the acidic endosomal environment?
Dissociation of the Translocation and catalytic subunits and translocation of the catalytic subunit into the cytosol.
What does the catalytic subunit do once released from endosomal vesicles in a host cell?
ADP-ribosylates EF2 and inhibits protein synthesis.
What is the ultimate result of protein synthesis inhibition?
Death of the cell
What are active cases of Diphtheria treated with?
Antitoxin against the receptor binding domain
Why can Antitoxin be detrimental to the patient?
Because it's produced in horses and can cause anaphylaxis.
When should patients that have been in contact with a Diphtheria infected individual be vaccinated?
If their last vaccine was more than 5 years ago.
For what pathogenic microbes are the vaccines made by formalin inactivation?
For what pathogenic microbe is the vaccine made by using whole killed bacteria?
Bordatella pertussis
Once a disease has been eradicated from a population, can you stop vaccinating individuals?
No; they tried that in Russia and now people are getting diphtheria there again