Bacterial Diseases Flashcards
What are the different shapes of bacteria?
- cocci (spherical)
- bacillus (rod)
- spirilli (twisted)
How is a Gram test performed?
- stain with violet dye and iodine
- rinsed in alcohol
- stained with red dye
What is the difference between Gram postive and Gram negative bacteria?
Gram positive:
- 1 membrane
- Cytoplasmic membrane with thick pept. Layer on
top
- peptidoglycan cell wall retains gram dye so deep
violet stain
single membrane with large peptidoglycan layer on top that traps dye to appear purple
Gram negative:
- 2 membranes
- Peptidoglycan sandwiched between membranes
- Both membranes have channel proteins
- Outermembrane composed mainly of
loppolysaccharide (LPS= - a PAMP) retains the dye
two membranes with thin peptidoglycan in-between so lose dye and appear pink
What occurs following Gram staining?
- Culture and microscopy
- Biochemical and serological tests
- DNA technique e.g PCR
-Determines antibiotic sensitivity so know which one
to give
What Gram type is Straphylococcus
positive
What Gram type is Streptococcus
positive
What Gram type is E.coli
negative
What Gram type is Salmonella
negative
What Gram type is Shigella
negative
What Gram type is Neisseria
negative
What Gram type is Cholera
negative
Name extracellular bacteria
- Staphylococcus
- Streptococcus
- Neisseria
Name intracellular bacteria
- Listeria
- Shigella
- Salmonella
- Mycobacteria
- Chlamydia
- Coxiella
What must bacterial Pathogens be able to do?
- Colonize: pili and fimbriae formed so can cling on surfaces
- Persist: ability to deal with immune system
- Replicate: acquire nutrients needed for replication
- Disseminate within cells, tissues, between organ and host
- Cause disease: produce toxins that will kill host cells, dysregulate immune responses
How does salmonella cause disease?
- polymerize actin into filaments (interference with actin cytoskeleton)
- Injects protein into cell membrane which ruffles in and bacteria stick in this ruffle
membrane detected, and proteins injected to make hollow pore in membrane (to move over bacterium) and to interfere with actin cytoskeleton to drive bacteria into cell
- As process dies down and returns to normal the trapped bacteria is internalized
How does Listeria cause disease?
Comet tails
- Breaks out of vacuole
- Assembles actin at one pole of cell
- Actin polymerization generates force propelling bacteria through cytoplasm
- Bacteria spread form one cell to another
What are the 3 types of horizontal gene transfer?
Transformation: suck up DNA from outside and recognize naked DNA
Transduction: DNA packaged into phage and then absorbed by other bacteriu
Conjugation: Physical bridge between bacteria allows plasmid transfer
How are upper respiratory tract pathogens acquired?
- Usually extrinsically acquired from rep tract droplets or airborne
- Hand transmission may act as intermediate
What bacterium causes yeast infection?
candida
What affects pathogenictiy?
Infectivity: ability to establish infection
- Transmission to host - Ability to colonize and replicate - Find niche - Evade immune system - Replication speed - Tropism and motlity
Virulence: features enhancing producing ability of pathogen
- Toxins - Enyzmes - immune system evasion - Interrupt normal host process
How does cholera cause disease?
- Makes 2 component toxin A and B which bind to GM gangliosides on gut which triggers cAMP production
- Chloride efflux
- Na and water flows out causing watery stools
Name 2 opportunistic pathogens
Gram negative: acinectobacter baumanii
Gram postivie: Straphylococcus epidermidesa
What are acid fast bacteria?
bacteria (particularly mycobacterium) that resist staining using an acid stain
