Lab Quiz 4 Flashcards
MacConkey
Selective (for G -) and differential:
Lactose fermenters = dark pink
Non-ferment = cream
Glucose, Lactose, Sucrose
Determines fermentation (bubbles) and pH with an indicator phenol red - turns red to yellow if +
Indole
Tests for the presence of indole, which results from cleaving tryptophan.
+ = red ring on the top of the medium
Needs reagent: 4-5 drops kovacs
Motility
Detects motility: streak vs diffuse through the medium
MR (methyl red)
VP (Voges)
Detect fermentation pathways by detecting different end products. Need to add reagents.
MR measures pH (less than 4.3 turns pink or red).
Needs reagent: methyl red
VP measures whether the organism used the butanediol pathway(+ = if acetoin is present; red/brick red precipitate)
Needs reagent. 10 drops VP-a with 5 drops VP-b and incubate for 30 mins
Citrate
Tests for citrate fermentation (the only C source),
pH indicator will turn the medium blue when rises (starts with a green color)
Urea Hydrolysis
Identify if bacteria can hydrolyse Urea + pH indicator
(turns pink via pH indicator)
XLD
Selective (for G-) and differential:
-Lactose/sucrose/xylose fermenters= orange
-non-fermenting=red
-HS producing=black precipitate
PAD (Phenylalanine Deaminase)
Differential:
PAD producers turn the top of slant media dark green
Needs reagent: 4-5 drops ferric chloride
HE
Selective (for G-) + Differential:
-Lactose/sucrose fermenters: yellow/red
-non-fermenters: blue-green
-HS = black precipitate
Oxidase
Add reagent to Q-tip
Detection of cytochrome c oxidase enzyme
+ = purple
Catalase
Needs reagent:Uses H2O2
Tests for the presence of catalase
+ = bubbles
α-hemolytic
partial lysis - green zone around colonies
normal microbiota
β-hemolytic
complete lysis of RBC- clear zone around colonies
beta=bad: suggests strep
γ-hemolytic (gamma)
no lysis- no clearing
normal microbiota
