BACTE LAB STREP AND STAPH

Created by

Jaymarie Seballe

Cards (64)

Catalase Test Purpose
To distinguish catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species.
Catalase Test Principle
Presence of the enzyme catalase from the bacteria is capable of converting hydrogen peroxide to water and oxygen.
Catalase Test Expected Result and Bacteria
(+) Bubbling (rapid and continuous) (Staphylococci & Micrococci)
(-) No or few bubbles (Streptococci & Enterococci)
Catalase Test Reagent
3% or 30% Hydrogen peroxide
Coagulase Test Purpose
To differentiate Staphylococcus aureus from CONS
Coagulase Test Principle
Bound aka “Clumping factor” – reacts directly with fibrinogen resulting to the precipitation of fibrinogen on the Staphylococcal cell, causing the cells to clump.
Free: a extracellular protein enzyme that causes formation of clot. The clotting mechanism involves activation of a plasma CRF, which is a modified or derived thrombin molecule, to form the a coagulase-CRF complex. This complex in turn reacts with fibrinogen to produce the fibrin clot.
Coagulase Test Expected Result and Bacteria
(+) Slide: Macroscopic clumping in 10 seconds or less (Staphylococcus aureus)
Tube: Presence of clot
(-) Slide: No clumping (CONS)
Tube: No clot
Coagulase Reagent
human, rabbit, or pig plasma (anticoagulated with EDTA)
2 forms of coagulase enzyme
Bound coagulase (clumping factor)
Free coagulase (Staphycoagulase)
Bound coagulase/ clumping factor
Slide coagulase Test
bound to the bacterial cell wall and reacts directly with fibrinogen in plasma
(+) S. aureus, S. lugdunensis and S. schleiferi
Free coagulase/ Staphylocoagulase
Tube Coagulase Test
extracellular protein enzyme (free coagulase) + CRF (coagulase-reacting factor)
In coagulase test, laboratory scientists should look for clot formation after 4 hours of incubation at 37 ° C. If no clot appears, the tube should be left at room temperature and checked the following day. Fibrinolysin activity is enhanced at 37 ° C.
Why do we need a coagulase negative test result to be confirmed with the tube method?
5 or 10-15% of S. aureus organisms do not produce clumping factor
Bacitracin Test Purpose
To distinguish staphylococci species (resistant) from micrococci (susceptible)
Bacitracin Test Principle
Bacitracin inhibits cell wall synthesis.
Bacitracin Test Expected Result and Bacteria
(+) ZOI of greater than 10 mm - susceptible (Micrococci)
(-) ZOI of 6mm - resistant (Staphylococci)
Bacitracin Test Materials
Bacitracin disks (0.04U) Mueller-Hinton or Trypticase Soy Agar
Microdase Test or Modified Oxidase Test Purpose
To differentiate micrococci from staphylococci
Microdase Test or Modified Oxidase Test Principle
Based on the detection of the enzyme oxidase. In the presence of atmospheric oxygen, the oxidase reagent and cytochrome C to form the colored compound, indophenol.
Microdase Test or Modified Oxidase Test Expected Result and Bacteria
(+) Development of a blue to purple-blue color (Micrococci)
(0) No change in color (Staphylococci)
Microdase Test or Modified Oxidase Test Materials
Microdase Disk
L-Pyrrolidonyl Arylamidase (PYR) Test Purpose
Presumptive identification of CONS and S. aureus
L-Pyrrolidonyl Arylamidase (PYR) Test Principle
The enzyme L-pyrrolidonyl arylamidase hydro- lyzes the L-pyrrolidonyl- β-naphthylamide sub- strate to produce a β-naphthylamine. The β-naphthylamine can be detected in the pres- ence of N,N-methylaminocinnamaldehyde reagent by the production
L-Pyrrolidonyl Arylamidase (PYR) Test Expected Result and Bacteria
(+) Bright red color within 5 minutes (S. lugdunensis, S. intermedius, S. schleiferi)
(0) No change in color or an orange color (S. aureus)
L-Pyrrolidonyl Arylamidase (PYR) Test Materials
L-pyrrolidonyl- β-naphthylamide substrate
N,N-methylaminocinnamaldehyde reagent
Susceptibility to Novobiocin Purpose
To distinguish CONS (susceptible) from S. saprophyticus (resistant)
Susceptibility to Novobiocin Principle
Resistance of S. saprophyticus to Novobiocin
Susceptibility to Novobiocin Expected Result and Bacteria
(+) ZOI greater than 16 mm - susceptible (other CONS)
(0) ZOI of 6mm - resistant (S. saprophyticus)
Susceptibility to Novobiocin Materials
Mueller-Hinton Agar or Sheep Blood Agar and 5 ug Novobiocin disk
Mannitol Salt Agar Purpose
MSA is a selective and differential medium useful for isolation of Staphylococcus species
Mannitol Salt Agar Principle
MSA contains 7.5% NaCl. Staphylococcus spp. (and some strains of salt-tolerant strains of Micrococcus and Enterococcus) are able to grow in this level of NaCl.
Mannitol Salt Agar Expected Result and Bacteria
(+) presence of growth (yellow zone around the colonies) (S. aureus)
(0) presence of growth (red zone around colonies) (S. epidermidis)
Mannitol Salt Agar Materials and contains
Mannitol Salt Agar
1 % Mannitol
7.5% salt
Laboratory Test For Staphylococcus
Catalase Test
Coagulase Test
Bacitracin Test
Microdase Test or Modified Oxidase Test
L-Pyrrolidonyl Arylamidase (PYR) Test
Novobiocin Test
Mannitol Salt Agar
Group A Streptococci Test
Bacitracin Test (Taxo A)
Bacitracin and Sulfamethoxazole-Trimethoprim Susceptibility Test
L-Pyrrolidonyl-Beta-Napthylamide Hydrolysis Test (PYR Test)
Hippurate Hydrolysis Test
Bacitracin test (Taxo A) Principle
determine the effect of a small amount of bacitracin (0.04U) on an organism
Bacitracin (Taxo A) Result and Bacteria
(+) presence of zone of inhibition around the disk (S. pyogenes)
(-) no zone of inhibition (other Beta Hemolytic groups)
Bacitracin Test (Taxo A) Materials
Bacitracin disks (0.04U) Mueller-Hinton or Trypticase Soy Agar
Bacitracin and Sulfamethoxazole-Trimethoprim Susceptibility Test Principle
Differentiation of Group A, B, and possibly C, F, or G Streptococci
BACITRACIN AND SXT TEST
Bacitracin SXT
Group A Strep Susceptible Resistant
Group B Strep Resistant Resistant
Not Group A or B Resistant Susceptible