I am about to perform the Coagulase test for detection of Staphylococcus aureus using citrated human plasma. Do you have any advices or recommendation regarding the best conditions, dilutions, precautions ?
Yeah, just use EDTA.
It really comes down to whether you are using the slide or the tube test.
Dear mohamed
for optimum performance of the test you can follow the instructions available in any practical bacteriology text book.
for optimum performance of the test you can follow the instructions available in any practical bacteriology text book.
ASM has a good lab protocol for this. Search on their Homepage (it may be in the Microbe Library).
0.5ml of plasma in the ratio of 1:4 take in a clean test tube to that 1 colony of test organism should be inoculated and keep it at room temperature for overnight....if solid coagulum is formed it is positive result for staph
EDTA Plasma is best to do, since citrate can be used as carbon source by the bacteria u will get false positive coagulation with citrated plasma and one more thing before performing coagulation test first check for auto agglutination Staph culture with drop of saline this will probably neglect the false positive results. Also use negative controls to confirm the results and as said by other use diluted plasma.
All the best.
I have the opinion that the coagulase test using tubes with rabbit plasma+EDTA, and 18h inoculum in BHI broth, following the instructions available in any practical bacteriology text book and those of the manufacturer, gives safe results.
I guess you'll do the coagulase test plate. What works for me better in the laboratory is: suspended the colony of S. aureus in 50 microliters of physiological saline solution. This suspension combine it on the plate with 50 microliters of plasma with EDTA and mix approximately 4 min because some strains have a slow reaction.
Hope you find it useful
or you can use DNAse medium, if you want to work reqularly, because there are some S.aureus isolates coalglase negative, be aware!!!!
as we perform here for coagulase test for screening of S. aureus, add 10 drops of citrated plasma in a test tube then add a 3-4 bacterial colonies, incubate it at 35 decgrees celcius then observe for any coagulum. Coagulase Neg Staph means no coagulum observe after 2 hours incubation while positive one formed coagulum.
Place 10 citrate plasma drops in a test tube and then add 3-4 bacterial colonies, incubation at 37 °. After 2 h observing clot formation. Coagulase Negative when no clot, while positive when clot forms after 2 h.
Coagulase can be performed either by a slide technique for free coagulase or test tube for bound coagulase to differentiate S, aureus from other staph spp. For the slide techniques a loop full of colonies are emulsified with saline on the slide, followed by loop full of citrate plasma. observe for agglutination indicating positive coagulase. In the test tube technique a 1/10 dilution of bacteria and plasma are mixed and incubated for 2 to 3 hours at 37*C. Coagulase positive when there's clotting and negative with no clotting.
- Badges
- Science topic
- Similar topics
- Biological Science
- Microbiology