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MLT-BiochemistryTest
Microbiology
Question | Answer |
---|---|
Coagulase test is used to? | To differentiate Staphylococcus aureus from other staphylococcus species. |
How does coagulase work? | Coagulase turns fibrinogen to fibrin(a visible clot). |
What is staphylokinase? | It can breakdown fibrin. So the coagulase test has to be examined after 4 hrs, but not more than 24 hrs. |
How does Urease test work? | It turns Urea to Ammonia, with indicator Phenol red turns to bright red. |
Condition for Urease test? | 18-24hrs at 37 degree celsius. PTC: Proteus spp. NTC: E.coli |
what is Beta-galactosidase (ONPG) test? | ONPG structure is chemically similar to galactose. It will be broken down by beta-galactosidase to Orthonitrophenol (yellow in colour) and galactose. For: Shigella sonnei PTC: E.coli NTC: Proteus spp. |
Nitrate reductase test? | To test the presence of nitrate reductase, Nitrate to Nitrite. For: some Enterobacteriaceae. Incubate the organism with nitrate broth overnight. Add 1ml of reagent A and 1ml of reagent B. Positive: Red. Negative: yellow. Confirmed with Zinc( to Red). |
PTC and NTC for Nitrate reductase test | PTC: E.coli NTC: Actinobacter baumanii |
Oxidative /Fermentation of glucose, O/F test is used for ? | To determine the way of sugar break down , which could be oxidation, fermentation or unable to utilise sugar. |
What is O/F medium? Content? | Hugh and Leifson medium. Low protein: CHO ratio semi-solid consistency to allow acid formed to permeate to the medium from surface. Bromothymol blue as pH indicator, turn yellow when acidic. |
How does O/F test work? | Prepare each test organism two tubes with O/F medium, one with paraffin oil on top. stabbing deep into the agar medium with a straight wire. Yellow-Green: Oxidative(Pseudomonas); Yellow-Yellow: Fermentative(E.coli);Green-Green: Asacharolytic(Alcaligenes) |
What is Aseculin Hydrolysis? | Aesculin will be broken down to Aesculetin and glucose. Asesculetin with Ferric citrate will form dark colouration. |
Aseculin test is used for? | Only Group D streptococci(Enterococci) can hydrolysis aesculin in the presence of bile salt. PTC: Enterococcus faecalis NTC: streptococcus pyogenes |
What is Kovac's reagent? | It indicates the formation of Indole. |
How does Indole form? | Tryptophan will be broken down by tryptophanase to form indole, ammonia, and pyruvate. |
PTC and NTC for indole-Kovac's test | PTC: E.coli NTC: Klebsiella |
Optochin sensitivity test? | To identify streptococcus pneumoniae from other alpha-hemolysis streptococci spp. Blood agar, incubate at 5% CO2, then add Optochin disc. Sensitive: Streptococci pneumoniae; resistant: Viridans streptococci |
What is alpha- and beta-hemolysis? | alpha hemolysis: partly hemolysis of RBC beta hemolysis: completely hemolysis of RBC |
Bacitricin sensitive test? | To identify streptococcus pyogenes from other beta-hemolysis streptococci. Sensitive: Streptococcus pyogenes(Group A) Resistant: Streptococcus agalactiae( Group B) |