BACTE LAB LA12 Flashcards
used to detect the presence of the catalase enzyme which breaks down hydrogen peroxide into water and oxygen
CATALASE TEST
use to differentiate staphylococci from streptococci
CATALASE TEST
Positive Result for CATALASE TEST
Presence of Bubbling
A small amount of bacterial culture is placed on a microscope slide, and a drop of 3% H2O2 is added
SLIDE (DROP) METHOD Catalase Test
A Bacterial sample is placed in a test tube containing 3% H2O2
TUBE METHOD Catalase test
A heavily inoculated agar slant is flooded with 3% H2O2, and bubble formation is observed against a dark background
TUBE (SLANT) METHOD Catalase Test
Test that differentiates Staphylococcus aureus from other Staphylococcus species
Coagulase Test
A suspension of bacteria in EDTA-treated rabbit plasma is examined for clumping, which indicates the presence of bound coagulase
Slide Coagulase Test
Bacteria are mixed in rabbit plasma and incubated. Clot formation within 24 hours indicates positive result. Used to free coagulase
Tube Coagulase Test
Organism that may show coagulase positive
S. aureus
selective and differential for Staphylococcus species. Containing 7.5% NaCl, which inhibits most non-staphylococcal bacteria, and mannitol a fermentable sugar
Mannitol Salt Agar Test
pH indicator for Mannitol Salt Agar Test
Phenol red
a supplemental test for S. aureus
DNAse test
result: Mannitol fermentation with yellow colonies
Suggestive of S. aureus which ferments mannitol
result: growth with pink/ red colonies
Suggestive of other staphylococcal species, which do not ferment mannitol
this test differentiates coagulase-negative staphylococci based on their susceptibility to the antibiotic novobiocin
Novobiocin Susceptibility Test
Plate used for Novobiocin Susceptibility Test
Mueller-Hinton agar plate, BAP
The amount of time for the culture with Novobiocin disk is incubated before ZOI is measured
18-24 hours
Novobiocin ZOI of greater than 16mm
Susceptible (S. epidermidis, S. lugdunensis)
Novobiocin ZOI of lesser than or equal to 16mm
Resistant (S. saprophyticus)
This test differentiates B-hemolytic Group A strep from other B-hemolytic strep based on susceptibility to bacitracin
Bacitracin susceptibility test
Plate used for Bacitracin susceptibility test
BAP
_____ units of bacitracin disk is placed on the heaviest growth areas and incubated at _______ for _______
0.04 units
35-37 deg C
18-24 hours
Bacitracin ZOI of greater than 10mm
Susceptible (S. pyogenes)
Bacitracin no ZOI present
Other B-hemolytic streptococci
used for differentiating Streptococcal based groups based on their resistance or susceptibility to trimethoprim-sulfamethoxazole
SXT Susceptibility Test
Resistant to SXT but susceptible to bacitracin
Group A Strep
Resistant to both SXT and bacitracin
Group B Strep
Susceptible to SXT
Other B-hemolytic streptococci
Differentiates Streptococcus pneumoniae from other alpha-hemolytic streptococci
Optochin Susceptibility Test
______________ organism is optochin sensitive forming a > 14mm ZOI around the optochin disk
Streptococcus pneumoniae
Detects the pyrrolidonyl arylamidase enzyme, which hydrolyzes the PYR substrates, producing a red color
PYR Test
PYR positive microorganisms
Group A Streptococci, Enterococcus spp., Some staphylococcus and enterobacteriaciae
PYR negative microorganisms
Group B Streptococci, and other non-group A, B, D streptococci
Identifies bile-esculin positive bacteria like Group D Streptococci and Enterococcus spp
Bile Esculin Agar Test
Positive reaction for Bile Esculin agar test
Dark brown/ black coloration
Distinguishes S. pneumoniae from other A-hemolytic streptococci
Bile Salt Solubility test
Turner and Schwartz +1 on Coagulase test
have small unorganized clots
Turner and Schwartz +2 on Coagulase test
have a small organized clot
Turner and Schwartz +3 on Coagulase test
feature a large organized clot
Turner and Schwartz +4 on Coagulase test
entire contents of the tube coagulated & unable
to be displaced when the tube is inverted
_______________ wire loops will cause false positive on Oxidase Test
Steel and nickel
Oxidase Test must be used not older than ________________
1 week
PYR Positive result will have the development of a ______________________
color within a minute of addition of the reagent
deep cherry red
PYR test stands for
L-Pyrrolidonyl- β-naphthylamide
A positive reaction ninhydrin test is indicated by the appearance of a ___________________ within 30 min
deep blue color (about the shade of crystal
violet)
The addition of bile salts also activates the
______________ and accelerates the natural lytic reaction
observed with cultures of pneumococci.
autolysins
