Staphylococcus Flashcards
Culture Medium
1) Sheep Blood Agar Plate
2) Colistin Nalidixic Acid Agar
3) Growth on MSA
4) Chromogenic Agar
Catalase test ( Differentiate Staphylococcus from Streptococcus)
=Hydrogen peroxide broken down into water and oxygen
= The positive result shows bubbles because of the catalase enzymes
= Staphylococcus is positive
Coagulase Test ( Differentiate Staphylococcus aureus from CoNS)
= fibrinogen converted to fibrin in the presence of coagulase enzymes
Side Coagulase Test
Clumping occurs in test indicating it is positive for S. Aureus
Tube Coagulase Test
Positive controls get and do not flow when inverted ( gel like)
Modified Oxidase Test ( Differentiate Micrococcus from Staphylococcus) Reagent?
6% tetramenthyl-p- phenylenediamine dihydrochloride in dimethyl sulfoxide
Modified Oxidase , Results?
Positive= dark blue to purple color ( cytochrome C)
Negative= no change in color ( brown)
Bacitracin Susceptibility Test ( Differentiate Micrococcus and Rothia from Staphylococcus)
Used as an inexpensive test for presumptive identification of S. Pyogenes
Helpfull in screening for GAS in throat culture
Bacitracin Susceptibility
B hemolytic colonies that grow and are susceptible to bacitracin are presumptively identified as S. Pyogenes .
Bacitracin Susceptibility Result
S pyogens is Susceptible to bacitracin
And Resistant to SMZ
Camp Test( Christie, Atkins and Munch- Petersen)
Presumptive identification of GBS
Hippurate Hydrolysis
Differentiating S. agalactiae from B- hemolytic streptococci
Sheep’s Blood Agar
=Medium large in size convex , creamy , dome shaped
= Beta hemolytic some staphylococcus spp have no hemolysis
= 5% is needed for this media
=Pigment: white to golden yellow
Colistin Nalidixic Acid Agar
= Selective medium for growth of gram positive bacteria
= The medium is blood agar base with antibiotics
Growth on MSA ( Mannitol Salt Agar )
= Staphylococci have the ability to tolerate high concentration of salt
= Selctive: contains salt
=Differential : differentiates SAU from staphylococci
= high salt (7.5%) selective
= Indicators: Mannitol Phenol Red
Chromogenic Agar
=SAU appears deep pink to fuchsia colonies
= S. epidermidis partially or completely inhibited
= S. saprophyticus appears turquoise
Side Coagulase Test
=Presumptive test , detects bound coagulase
=Reagent used is plasma, could either rabbits or human plasma
=Plasma w/ anticoagulant
=Serum w/out anticoagulant
Tube Coagulase Test
= Confirmatory test , detects free coagulase
= Incubate for 4 hours if there is clumping note positive for tube coagulase
= If ever no clumping re incubate upto 18 hrs
Novobiocin Susceptible Test
Differentiate S. Saprophyticus from other CoNS
