Modules 8 & 9: Catalase, Nitrate, Coagulase, DNase, Beta-lactamase; Staphylococcus Flashcards
Beta hemolysis
Complete clearing of red blood cells around colony
Alpha hemolysis
Partial clearing of red blood cells, greening around colony
Gamma hemolysis
No clearing of red blood cells around colony
Bacteriophage testing
Used to type S. aureus strains
Virus specific to bacterial strain
Bacteria lyse, plaques form
Bound Coagulase
Slide Coagulase test
Differentiates S. aureus from CNS
Bound into cell wall, acts on fibrinogen to form clot
Catalase
Use chocolate agar (BAP=false positive) Reagent is H2O2 Genus test for Staph (+) and Strep (-) Enzyme forms bubbles(O2) Platinum wire causes false positive
Clumping factor
Bound Coagulase
Detected in slide Coagulase test
DNase
Depolymerizes DNA into oligonucleotides HCl: pos=clear zone, neg=precipitate Methyl green: pos=clear, neg=green Toluidine blue: pos=pink, neg= blue Virulence factor
Exotoxin: enterotoxin
Preformed toxin
S. aureus food poisoning (1-6 hours)
Affects intestinal cells, lack of absorption, diarrhea, vomiting
Facultative anaerobes
Can grow in AnO2 and O2 conditions, grows better in O2
Free Coagulase
Determined with tube Coagulase test Exuded into environment, not bound to cell wall Extra cellular enzyme SA= pos CNS= neg
Hemagglutination test
Test for S. aureus
Similar to slide Coagulase, quicker
Visible agglutination with reagent and Staph cells
Induced beta-lactamase
Grow organism in presence of beta lactam antibiotic to induce expression of beta lactamase enzyme
Staphylokinase
Clot buster
Allows spread into tissues
Latex reagent
Test for SA
Visible agglutination with the reagent latex particle attached to SA cells
Leucocidin
Chemical produced by some bacteria
Kills phagocytic white blood cells
Micrococcus
Same family as Staph
Bacitracin test differentiates Staph from Micrococcus
Micrococcus=susceptible
Staph=resistant
Nitrate test reagent A
Sulfanilic acid in acetic acid
Nitrate test reagent B
Alpha naphthylamine in acetic acid
Novobiocin
Disc test for S. saprophyticus
12mm = susceptible (other CNS)
Oxacillin screen test
MRSA test
Agar dilution test with 6ug/mL oxacillin in plates
Growth = resistance (MRSA)
No growth = sensitive
Phenol red
Indicator in MSA agar
Works with mannitol to differentiate SA from CNS
Concentration of peroxide for catalase test
3%
Protein A
Cell wall protein in S. aureus
Binds Fc portion of IgG
If present, IgG and attached latex will be bound by Staph cells = agglutination
Pulse field gel electrophoresis
Cleave sections of bacterial chromosome
Separate on gel and stain
Provides DNA fingerprint
Compare to known DNA fragments
Catalase QC organisms
Pos: any Staph species
Neg: stick or any Strep species
Coagulase QC organisms
Pos: S. aureus
Neg: S. epidermidis
Rabbit plasma
Used for Coagulase test
Available commercially
Does not need to be screened for HIV of hepatitis
Store in fridge, clear bottle
Slide Coagulase
Detects bound Coagulase
Differentiates SA from CNS
S. lugdunensis Coagulase
Slide +, tube -
S. saprophyticus Coagulase
Slide -, tube -
S. schleferi subspecies coagulans Coagulase
Slide -, tube +
S. schleferi subspecies schleferi
Slide +, tube -
Tube Coagulase
Detects free Coagulase
Use rabbit plasma in test tube
Thermostable nuclease
Produced by S. aureus
Not produced by other bacteria
Test not technically suited for routine ID
Useful for investigation of food poisoning
NaCl concentration in MSA
7.5%
