Lab Practical Flashcards
What does gram positive bacteria look like when stained
purple
What does gram negative bacteria look like when stained
pink
What does a PEA test do and is it a differnetial media
Selects for gram positive and inhibits gram negatives, is not differential
What does MacConkey agar do and is it a differential media
Selects for gram negative and inhibits gram positive, is didfferential. If pink or red, then ferments lactose producing acidic byproducts if white or clear, then unable to ferment lactose but ferments peptone producing alkaline byproducts
What does mannitol agar do and is it differential
selects for gram positive staph only and is differential. If yellow then it ferments mannitol creating acidic byproducts if red then no fermentation of mannitol
What does phenyethanol agar do
Selects for gram positive and inhibits gram negative
What does Voges-Proskauer test do
Differential test that when red (positive) indicates break down of glucose but if copper (negative) indicates no breakdown of glucose; differentiates between members of the enterobacteriaceae
What does a methyl red test do
Differential test that if red (positive and acidic) indicates glucose fermentation via mixed acid pathway yellow if negative; differentiates between members of the enterobacteriaceae
What does an indole test do
Differential test that if red ring appears (positive) indicates hydrolyzation of tryptophan into indole
What does a citrate test do
blue for use of citrate as sole carbon source or green for lack of citrate
What does blood agar do
inidicates hemolysis breakdown. (GA CB RG) If green, then alpha hemolysis and partially degrades RBCs, if clear then beta hemolysis and complete deagradation of RBCs, and if red then gamma hemolysis and no degradation of RBCs
What does a urease test do
Test if urease is produced which hydrolyzes ammonia and CO2. If pink, then urease is produced alongside alkaline conditions and if yellow then no urease indicating acidic conditions
What does a catalase test do
If positive, bubbles will produce indicating production of catalse. Staph are positive while strep are negative
What does an oxidase test do
Indicates if aerobic respiration is done by testing for presence of cytochrome oxidase. if positive, dark blue or purple will appear, clear if negative
What does triple sugar iron agar do
differential medium for fermentation of glucose, lactose, or sucrose. Yellow bottom, red top indicates fermentation of glucose only. Red bottom and top indicates fermentation of nothing. Yellow bottom and top indicates fermentation of glucose and lactose and/or sucrose. If black precipitate then hydrogen sulfide is produced. Bubbles indicate fermentation produces gas therefor must be yellow portion
What does a nitrate reduction test do
determines if nitrate is reducred to nitrite and further reduced to nitrogen gas. If red, then nitrite is produced. If no red then zinc is added and if red then nitrate is not redcued. If no red, then nitrate is reduced to nitrogen gas
What does a decarboxylase test do
tests for presence of enzyme in acidic conditions resulting in alkaline conditions. If yellow to purple then enzyme if produced but takes time
What does a DNase test do
tests for staph via deoxyribonuclease activity. Positive if clear around colonies on green agar plate
What does a coagulase test do
Tests staph for coagulase. Positive if cloudy in plasma
What does a PYR test do
If red (positive) then group A strep and group D enterococci and if orange/yellow (negative) then group B strep, V. strep, or beta strep
