WEEK 7!!!

Hello everyone!! HOw are your SIP??.. I hope everything's okay, Well I'm having a great in my Micro Lab. For now, I'm in the investigation lab for 1 month where they try to identify the microganisms in the patient's samples. There are quite a number of tests carried out, especially all the biochemical tests( i hope you guys remember). For this week, I learn more about Streptex. I know you guys will be like, "HUH What is Streptex??" . Ok let me tell you...




Streptococcus Latex Agglutination (Streptex)




Streptex is used to identify the Lancefield groups of Streptococci growing on agar plates



Principle


Lancefield showed that the soluble extracted antigens can be identified by precipitation reactions with homologous antisera. Now, latex agglutination or coagglutination methods have largely superseded precipitation method in determining the different groups. A simple enzyme extraction procedure is carried out. Antigen in the resulting extract is identified using polystyrene latex particles which have been coated with group-specific antibodies. These latex particles agglutinate strongly in the presence of homologous antigen and remain in smooth suspension in the absence of homologous antigen.


Materials Streptex Kit

• Streptex Kit contents:Latex for Group A,B,C,D,F,G, extraction enzyme, disposable mixing sticks, disposable reaction cards,


• Disposable Pasteur pipette


• Disposable inoculum loops
  

Procedure

Preparation of extract from culture growing on solid medium:
1. Dispense 0.4ml Extraction Enzyme into an appropriately labelled test tube for each culture to be grouped. (Usually around 20-30 tubes of 0.4ml Extraction Enzyme are prepared at the same time)
2. Using a disposable inoculums loop, make a light suspension of the culture in a tube containing the enzyme solution.( A single sweep of growth or > 5 large colonies will be sufficient to obtain a result)
3. Incubate the suspension at 35⁰C in an incubator for at least 10 minutes


Group Identification:
1. Resuspend each of the latex suspensions by shaking vigorously for about 5 sec (The kit contains 6 bottles, one specific for each of the groups A,B,C,D,F and G)
2. Expel the contents of the in-dwelling droppers to ensure complete mixing.
3. Dispense one drop (20µl) of each latex suspension onto a separate circle on a clean reaction card.
Note: Dropper bottle should be held vertically to ensure that the drops form at the tip of the nozzle. If the nozzle becomes wet, an incorrect volume will be form around the end and not at the tip.
4. Using a Pasteur pipette, place 1 drop of extract in each of the 6 circles on the reaction card.
5. Mix the contents in each circle in turn with a mixing stick, and spread to cover the complete area of the circle. Use a separate stick for each circle and discard it for safe disposal after use.
6. Rock the card gently for a maximum of 1 min, holding it at a normal reading distance (30cm) from the eyes.
7. Discard the card for safe disposal

8. Keep the reagents back into the refrigerator, using the storage rack provided.











Positive result showing agglutination clumps:

Conclusion








Positive result will show development of an agglutinated pattern showing
clearly visible clumping of the latex particles. Speed and quality of agglutination appearance depends on the strength of the antigen extract. Strong antigen extract will give large clumps of latex particles within a few seconds after mixing. Negative result will show no agglutination and the milky appearance remains unchanged throughout the test. There should only be one latex suspensions showing strong rapid agglutination.

So thats about all!! SEE YOU SOON!!!

AmiR ArshaD

TG02