Commensalism vs Pathogenicity Flashcards by Stephanie Cortes

What is mutalism?

Both organism 1 and 2 benefit

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What is commensalism?

Organism 1 benefits, nothing happens to organism 2

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What is parasitism?

Organism 1 benefits, organism 2 is harmed

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Most of our normal flora are what type of -ism?

Commensalisms

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What commensalism are found on our skin?

Gram + cocci and yeast such as; S.epidermidis, C.albicans, S.aeuros - Stay commensalism’s if kept in proper compartment (outside of skin)

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Opportunistic infections?

Organism that were not harmful, become pathogenic if the opportunity presents itself.

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Ex of opportunistic infection on skin?

S.aeuros can cause a wound INFECTION in an injured person

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Commensalism’s found in Nose/Throat?

Strep, Staph, Neisseria - Stay commensalism’s as long as kept in proper compartments AND person is immunocompetant

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Ex of opportunistic infection in Nose/Throat

If Neisseria gets into the blood stream (outside of its compartment) it can cause meningitis in an unvaccinated person (non-immunocompetant–>immunosupressed)

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Commensalism’s found in Mouth?

Actinomyces, Kingella kingae

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Ex of opportunistic infection in Mouth? #1

Actinomycosis - if actinomyces escapes oral cavity into jay/lymph-nodes–> formation of a “benign tumor”

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Ex of opportunistic infection in Mouth? #2

HACEK endocarditis - caused when a group of organisms from the mouth enters the blood stream and causes heart valve problems

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Commensalism’s found in GI track?

Large #! - Stay commensalism’s as long as kept in proper compartment AND the balance of microorganisms is correct (Antibiotics can thrown the #’s off)

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Opportunistic infections in GI track?

Sepsis following colonic rupture.
Pseudomembranous colitis - gut obstruction, do to course of abs (overgrowth of certain bacteria causes this(
Antibiotics present - throw of flora –> diareah

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Microorganism in Vagina?

Symbiote - Lactobacillus

Commensalism - Candida

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What is colonization resistance?

A form of symbiosis in which even commensals can participate in

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Steps in colonization of new bacteria

New bacteria introduced–>either colonizes or doesn’t
If is doesn’t colonize –> the PATHOGEN or non-pathogen is cleared
If colonizes –> and is non-pathogenic it becomes commensalism, but if it is pathogenic it will cause a disease
If the pathogen causes a disease –> it can kill the host OR the host becomes chronic carrier OR host kills pathogen

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How would a pathogen (which did not colonize) be cleared?

Role of colonization resistance

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How does colonization resistance work?

There is other bacteria (harmless) taking up space, that the new bacteria (harmful) needs in order to reproduce and survive. The pathogen must be very pathogenic in order to outcompete present bacteria.

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What is a non-pathogen?

Very unlikely to cause disease
Most environmental bacteria and the normal flora are non-pathogenic
Very low virulence –> LD 50 - very high, ID 50 - high

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What is a opportunistic pathogen?

Unlikely to cause disease in a healthy individual
Will take advantage of injury or immunosuppression (age-infant an the ealrderly)
Low virulance –> LD 50 - high, ID 50 - mid-low

Ex of opportunistic infections?

Legionella, Pseudomonas, Enterobacter

What is a pathogen?

Readily causes disease in previously healthy individual

Mid-High virulance –> LD 50 mid-low, ID 50 low

Ex of pathogens?

N. gonorrheae, Shigella, Norwalk Virus

What is ID?

Infectious dose - # of bacteria needed to cause colonization

What is LD?

Lethal dose - # of bacteria needed to kill an individual

What is virulence?

description of pathogenicity, how much is needed to cause disease

What are virulence factors?

Genes found empirically to be determinants of pathogenicity

What do virulence factors help with?

``` Survive extreme environments Adhesion Immune evasion Host cell takeover Poison the host ```

What are some virulence factors that help pathogens survive extreme environments

pH tolerance, siderophores, resistance to drying, resistance to detergents

What are some virulence factors that help pathogens adhere?

Pili/Fimbrae/Curil - specific/non-specific Slime Layer - non-specific Adhesins - specific

What are some virulence factors that help pathogens with immune evasion?

``` Capsule IgA protease Macrophage Apoptosis Inducers Antigenic Variation Serum Resistance ```

What are some virulence factors that help pathogens take over the host cell?

Endosome Escape Routes Actin Polymerization Pathways T3SS/T4SS

What are some virulence factors that help pathogens poison the host?

Tissue-Degrading Enzymes Endotoxins - part of bacteria Extotoxins

What are EXOtoxins?

Are polypeptides that are either secreted from the cell or injected by T3SS. The most TOXIC substances known

What are some common toxic strategies used by exotoxins?

Superantigenicity Interference with signal transduction Depolymerization of actin

What is A-B subunit? What is it used for?

Several exotoxins have a similar A-B Subunit Structure. | B delivers A to site of A's toxic activity -- one common activity for A is ADP-ribosylation

Are exotoxins heat liable?

Yes. The heat unfolds them, and have a hard time refolding (inactive toxins). Useful for vaccines

What are superantigen exotoxins? Superantigenicity

Undermine specificity of immune response (25% instead of 0.0001-0.001%) Can cause shock or multiple organ failure

What are some common bacteria that cause Superantigenicity?

Staph aureus Strep pyogenes Both cause TOXIC SHOCK SYNDROME

What mechanism do gut bacteria Cholera, E.coli and B. cereus toxins use?

Increase adenylate cyclase activity | Causing fluid and electrolyte loss

What do C. difficile toxins A and B do?

Glucosylate Rho GTPase--> leads ti depolymerization of actin, apoptosis, and a major inflammatory response in the gut

What does Diphtheria Toxin do?

Tox gene encoded by lysogenic bacteriophage | Look up what it does??

What does MRSA OV leukocidin do?

Forms pores in cell membranes --> lysis | PVL genes are phage born

What is Koch's Postulate?

Is a way to determine that a certain pathogen causes a certain disease.

What are the steps to Koch's Postulate?

``` Observe pathogen in sick animal Grow pure culture of pathogen Infect new animal from pure culture Observe same disease in new animal Obtain pure culture of same pathogen from new animal ```

What are the steps from Illness to Recovery?

``` Infection Incubation Period Prodrome Specific-Illness Period Recovery/Covalescence ```

What makes up the infection step?

Pathogen Defeats Innate Immunity for Successful Colonization

What makes up the incubation period?

Microbial numbers too low to produce symptoms, most rapid growth

What makes up the prodrome period?

Nonspecific immunogenic symptoms as adaptive immunity is raised: fever, fatigue

What makes up the specific illness period?

Pathogen-Mediated symptoms emerge as large numbers of pathogens express virulence factors

What makes up the recovery/covalescence?

Immune system gains upper hand and dramatically reduces pathogen numbers; patient begins to regain strength