Lab final Flashcards
high temperature effect on microbes
impact metabolism, enzymes denature, lipids of membrane destroyed
-microbicidal
low temperature effect on microbes
slow cell growth bc chemical rxns are reduced, reduced fluidity of membrane, de crease rate of nutirents crossing into cell
-microbistatic
psychrophiles
-5 to 20
meophiles
10-50
thermophiles
45-80
troph
wider temp range
disinfectants
cause injuries to cells
brief exposure
single hole in the cell membrane
-dilutes difinfectants power
-need many holes to kill the cell
How to increase disinfectant effectiveness
-increase concentration of disinfecting agent and increase the amount of time that the chemical is left in contact with the microorganisms
hospital disinfectant (has to pass what test)
has to pass the use-dilution test to see how well it works against high microbial load dried on a hard nonporous surface
cylinders soaked in
staphylococcus aurerus, salmonella choleraesuis, pseudomonas aeruginosa
selective
certain microbes can grow
differential
microbes that grow will be a diff color
mannitol
-selective and differential, isolate staphylococci
-carbon source: carbohydrate mannitol
-selective agent: NaCl
-phenol red: detects fermentation of mannitol to acidic products
Pink —> yellow (ferments mannitol)
MacConkey
-selective and differential
-has bile salt and crystal violent to select for gram (-)
-carbohydrate lactose and PH to detect lactose fermenters vs non fermenters
Pink/purple —> deeper pink (lactose fermenting)
Pink/purple —> yellow (non lactose fermenting)
eosin methylene blue agar
-selective for gram (-)
-eosin and methylene blue dyes inhibit the growth of gram (+)
-differential with lactose fermenting bacteria bc they will make a blue-black color that are visible while the non lactose fermenting colonies will be colorless/ amber
hektoen
-selective for gram (-)
-shigella and salmonella
-bile salts inhibit gram (+)
-three carbohydrates can distinguish between enteric bacteria
-production of hydrogen sulfide = salmonella NOT shigella
TSA
-triple sugar iron agar
-differential medium to see if sugar, glucose or lactoe are fermented
-also detects the production of hydrogen sulfide and gas
-identifies gram (-)
oxidase
determines if bacteria has cytochrome C oxidase (enzyme in etc of some bacteria)
-differentiates oxidase (+) pseudomonas from oxidase (-) enterobacteriacaea
shortes waves
gamma and x rays
-sterilize heat sensitive objects like plastic but the level of radiation is toxic
longer waves
uv light, infared, visible light
-can form free radicals in organisms
UVC
for bacteria bc it creates pyrimidine dimers for new covalent bonds between pyrimidines
-mess up DNA helix kills cells if there are enough dimers
-lower energy= safer to work with
Kirby bower
higher concentration is closer to the disk
-zone of inhibition is where the microbes cant grow can be measured and used to compare to standard to find if microbe is sensitive or getting resistant
-can help us determine selective toxicity bc other bacteria not pathogen should be unaffected
-also lets us determine therapeutic dose
Zone of inhibition
depends on molecular weight of the antimicrobial, type of media, concentration of bacteria culture
-use turbidity
An area of media where bacteria can’t grow due to presence of a drug that impedes their growth
kirby bauer standard media
meuller hinton 2
tube dilution
takes kirby bower results further to get the minimum dose to kill the bacteria
-MIC
