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can distinguish among morphology and biochemically related groups of bacteria. chemically altar bacteria to show a physical change in appearance of bacterial growth or medium surrounding the colonies, sometime differential and selective media characteristics can be combined.
media that have been supplimented with high nutritious materials to cultivate fastidious organisms
7.5% sodium chloride agar
inhibitory to most organisms, detects for salt loving organisms (halophilic) most useful in detection of staphylococcus
Mannitol salt agar
contains a high salt concentration, PH indicator for detecting acid. detects for staphlycocci-->yellow zone around bacteria if it ferments the mannitol salt
allows the isolation of gram negative two groups: coliform bacilli and (dysentery, typhoid and paratyphoid bacilli)
Dysentery, typhoid and paratyphoid bacilli
non lactose fermenters, and therefore appear transparent (no lactose, no color)
selects for gram positive, and lactose positive. e.coli will have a blue-black with a metallic green shine
lysis of red blood cells with complete destruction and use of hemoglobin by the organism results in a clear zone surrounding the colonies (shiny glowing yellow green)
Triple sugar iron (TSI) agar test
designed to differentiate among the different groups of the enterobacteriaceae which are all gram negative bacilli capable of fermenting glucose with the production of acid AND to distingiush between other gram negative intestinal bacilli
Alkaline slant (red) and acid butt (yellow) with or without gas production (breaks in the agar butt)
Acid slant (yellow) and acid butt (yellow) with or without gas production
eats sugars (lactose and sucrose)
Alkaline sland (red) and alkaline butt (red) or no change (orange-red) butt
both reactions the same, eat protein-->basic (non acidic)--> so therefore remains red
TSI COLOR CHANGE
the acid-base indicator phenol red is also incorporated to detect carbohydrate fermentation which turns the medium to yellow in the presence of acid
Normal intestinal flora
Escherichia and enterobacter, which are saprophytic members of the intestinal tract
tests for e.coli and turns cherry red if indole positive, however the have to be careful or red pigment vs red chunks (24-48 hrs) Kovac's reagent-->produces the cherry red layer
medium becomes alkaline, this medium turns from green to deep prussian blue (if blue it is citrate positive)
Methyl Red Test
separation of e.coli and e. aerogenes. turn yellow if a negative test, and red if a positive test (tests for presence of ACID)
forming a soluble black ferrous sulfide precipitate seen along the line of stab inoculation, H2S is present (positive) if a pipe cleaner thing is present. culture growth not restricted to line of inoculation. SALMONELLA WILL BE BLACK BUTT
identifies proteus vulgares, if ammonia present, it causes the phenol red to turn a deep pink (super base)
Phenylalanine Deaminase Test (PPA agar)
identifies proteus, if color reaction turns green, its positive THEN dissapears. reageant--> 10-12% ferric chloride solution
chemical substances that destroy or inhibit the growth of microorganisms in living tissue (antibiotics/synthetic drugs)
living bacteria, actinomycetes and fungi that destroy the growth of other microorganisms
Length of exposure
sensitive forms destroyed more rapidly than resistant ones (environment and consistency must also be considered)
Types of microbial population to be destroyed
spores--> resistant, acid-fast-->more resistant than non acid-fast, older less active cells more resistant than young cells
the increase in temp increases the rate of reaction in which cells are killed by the chemical reaction taking place
pH conditions affect the microorganism AND the compound, extreme pH are harmful to microorganism but also increase the antimicrobial action of a chemical
Types of mediums
the microorganism may not stand a change against the combo of chemical and organic cellular molecules
Phenol Coefficient test
determined by dividing the highest dilution of chemical being tested that destroyed the microorganism in ten minutes but not five minutes
A mueller hinton tellurite or tinsdale agar plate detects
cornyebacterium (diptheroids), or colonies with a black appearance
Sabouraud agar plate detects
yeast; mold colonies will appear fuzzy, powdery growths arising from a mycelial mat
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