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18 Cards in this Set

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Alterations in normal body bacteria flora...

→ in immune dysfunction

C. diff is associated with...

Antibiotic Associated Colitis

Bacteria

Prokaryotes


lack a nucleus


no membrane bound organelles




slimy capsule

Gram stain


explain the process?

1. stain with crystal violet + iodine


2. wash the cells with iodine


3. counterstain with safranin




4. if they retain the crystal violet + iodine = Purple, Gram Positive


5. if they retain the safranin = Pink, Gram Negative

Gram positive bacteria


type of layers on cell membrane?


thickness of cell membrane?

Peptidoglycan only
Thick cell wall

Peptidoglycan only


Thick cell wall

Gram negative bacteria


type of layers on cell membrane?


thickness of cell membrane?

Peptidoglycan + Lipopolysaccharide LPS or Endotoxin


Thin cell wall 
outer layer heavily modified with sugars

Peptidoglycan + Lipopolysaccharide LPS or Endotoxin




Thin cell wall


outer layer heavily modified with sugars

LPS


what is it?

potent activator of the immune system




→ endotoxic shock e.g. meningococcal sepsis



Peptidoglycan cell wall


implications for treatment?

target for many ABX etc.

MALDI-TOF MS




technique?


what does it allow you to do?

Matrix Assisted Laser Desorption Ionization-Time Of Flight Mass Spectrometry




expose bacteria colony from sample e.g. stool, CSF,


analysis of mass of fragmentation → identification of organisms by a database

How Bacteria → Disease:




Overview

1. Attach to host


2. Invade tissue


3. Acquire nutrients and grow


4. Avoid host immune response


5. cause damage - presents as the signs and symptoms of disease



Virulence factors


what is the definition?

factors that allow pathogens to cause disease

How Bacteria → Disease:


Attachment

Pili/Fimbrae


by attaching to host receptors


can be taken up


then intracellular survival occurs

E. Coli is an intracellular bacteria

E. Coli expresses FimH which means it evades phagocytosis

How Bacteria → Disease:


Invasion


Type 3 secretions




what is it?


example bacterium?

Type 3 Secretions:


https://www.youtube.com/watch?v=gnNFNI9_pT0




injects host cell with effector molecules → alter cytoskeleton of cell → promotes bacteria uptake




e.g. salmonella





How Bacteria → Disease:


Invasion


Nutrient acquisition e.g. Fe

Nutrient acquisition -


acquiring Fe


most Fe is bound to transferrin


bacteria make siderophores have high affinity for Fe and scavenge it from host proteins

How Bacteria → Disease:


Invasion


Mechanism of Immune evasion

How Bacteria → Disease:


Damage




Direct mechanism...


Indirect mechanism...

Direct - via toxins e.g. membrane damaging, neurotoxins, tetanus, botulinum




Indirect - over activation of inflammation e.g. LPS over activation of cytokines in sepsis,




Molecular mimicry - microbial components are similar to host e.g. Group A Streptococci, Acute Rheumatic fever

CLINICAL APPLICATION:


Toxic Shock Syndrome

When Staphylococcal aureus toxin → toxic shock