Lab Final: tests to study Flashcards
Selective
inhibits the growth of certain organisms and thus selects for growth of another
Differential
distinguishes one microbe from another, usually by color
What plate is differential only?
BAP BLOOD AGAR PLATES
What plate is selective only?
PEA PHENY ETHYL ALCOHOL
What plate is both selective and differential?
MSA MANNITOL SALTS AGAR
D. MAC MacCONKEY AGAR
E. EMB EOSINE METHYLENE BLUE
What does BAP look for?
Hemolysis
Types of Hemolysis on a BAP?
Beta hemolysis = clear zone surrounding perimeter (see through)
Alpha hemolysis = olive green or brown colored zone
Gamma = no zone or no-hemolysis (non-hemolytic).
What makes PEA selective only?
Only Gram Positive bacteria grow on it
Examples:
Gram negative bacteria is prohibited by ETHYL ALCOHOL
STAPHYLOCCOCCI AND BACILLUS
What makes MSA selective and differential?
Selective: Salt (NaCl), Staphylococcus species (halophiles) will grow on this agar
Colonies= halophile (Staph species)
Differential: Mannitol sugars, Staph aureus ferments mannitol and turns the agar yellow
Yellow= mannitol fermenter
What makes MAC selective and differential?
Selective: only for Gram negatives organisms, gram positive inhibited by bile salts, crystal violet dye, and neutral red dye
Colonies = gram negative organisms
Differential: Lactose bonded to a pink dye
Pink colonies = lactose fermenters
What makes EMB differential and selective?
Selective: only for Gram negatives, gram positives are inhibited by Eosin Methyl Blue dye
Colonies = gram negative organisms
Differential: Lactose bonded to a pink dye
Purple color = lactose fermenter
What organism makes a green shine on and EMB plate?
E. coli, Citrobacter freundii, and Klebsiella oxytoca
What is in a TSIA tube?
Slant = Sucrose and Lactose
Butt = glucose
What makes H2S present in TSIA?
Iron
What does an SIM tube test?
Sulfide, Indole, motility
What is the proper transport medium?
Stuart’s Transport Medium
How much urine does a calibrated loop hold?
.001 mL or 1 microliter
Urine specimen classification
0-9 = insignificant
10-99 = infection
>100= acute infection
What do you multiply the colonies of a urine sample by?
1,000
What reagent is used for a catalase test?
Hydrogen peroxide
What is catalase test used for?
Identifies the Gram (+) cocci genus Staphylococcus (any species) from the Gram (+) cocci genus Streptococcus (any species).
Catalase test results
Bubbling is a (+) reaction =All Staphylococcus species
No bubbling is a (-) reactive = All Streptococcus species
What is used in a coagulase test?
Rabbit plasma
What is a coagulase test used for?
identifies Staphylococcus aureus from Staphylococcus epidermidis
Coagulase test results
The presence of clotting is a positive reaction.(+) = S. aureus
The absence of clotting is a negative reaction. (-) = S. epidermidis
What is the bacitracin test used for?
Gram-positive cocci is Catalase (-), it is a species of Streptococcus
specifically identifies Streptococcus pyogenes = Strep group A
Bacitracin results
Zone of inhibition around bacitracin disk is positive for S. pyogenes
No Zone of inhibition means
What is the CAMP test used for?
when the Bacitracin Test is (-) and the Streptococcus species is not S. pyogenes
test confirms Streptococcus agalactiae = Strep group B
CAMP test result
Arrowhead clearing is (+) for the CAMP test. The pathogen is S. agalactiae
A negative CAMP test means that the Streptococcus is yet another Streptococcus species and not S. agalactiae
What is the Oxidase test used for?
differentiate Gram-Negative rods of the Family Enterobacteriaceae from those organisms that are Non-Enterobacteriaceae
Oxidase test results
Purple color = positive test = Pseudomonas and Acinetobacter
No color = negative test = Family Enterobacteriaceae
METHYL RED (MR) TEST results:
A red color is a positive (+) test result = acid was produced.
A yellow color indicates a negative (-) reaction
What reagent is needed in a MR test?
Methyl Red Reagent
VOGES PROSKAUER (VP) TEST
The cherry red color is Positive (+) = presence of acetoin, the product of the reaction from glucose fermentation .
A yellow color indicates a negative (-) reaction
NUTRIENT GELATIN TEST: result
Gelatin is a liquid = Positive (+) for gelatinase
Gelatin is a solid = Gelatinase is absent (-)
VOGES PROSKAUER (VP) TEST: reagents
Alpha-Naphthol Reagent, followed by KOH (Potassium Hydroxide) Reagent
