Microbiology

Hello children!!!!

Haiz, so refreshing to go back to school for a change. Nonetheless, i must admit that i'm getting a little too used to the ole working life. Haha. I know some of you already are enjoying yourselves riiight.

So anyway, its been 10weeks (no way man!) and I've been posted to almost all the benches in my lab - urinalysis, microbiology, hematology, blood banking, order entry and clinical chemistry. Next month, i might even get a chance to follow the phlebotomists on their rounds to the wards and observe how they draw blood. Super cool. And and! Recently, Pei Shan (we're in the same lab) & I underwent a Point-of-Care Testing training as we will be sent out to do an Outreach Programme next month at a shopping mall. Ultra cool. So I guess that means, I can go back to school and apply my finger-pricking skills to my classmates. Mwahaha.

I'm sorry, I'm too used to digressing. So this week, i'm going to blog about a Stool Toxicological test using a testkit called ImmunoCard.

Name of Test: Detection of Clostridium difficile Toxin A & Toxin B in Stool

Introduction:
Clostridium difficile is a species of gram-positive rod-shaped bacteria that is the main cause in infectious diarrhea. Most strains of this bacteria produce 2 biologically and immunologically different toxins: Toxins A & B. A rapid test such as this ImmunoCard test enables the physician to verify any possible infection quickly and begin treatment immediately.

Principle:

• This is a rapid enzyme immunoassay
• Consists of a membrane held in a plastic frame with 2 sample ports and 2 reaction ports. The left-hand side column represents the Control panel while the other column represents the Test panel.
  

• This membrane contains immobolized antibodies to Toxins A & B. An Enzyme Conjugate, Wash Buffer, Substrate Reagent and Specimen Diluent is also provided along with the kit. The Enzyme conjugate contains antibodies to Toxins A&B coupled with horseradish peroxidase. The diluent is a buffered protein solution.
• Patient stool sample is diluted with the Specimen Diluent and the Enzyme Conjugate is added to it. It is then incubated for 5 mins. During this time, if there is toxin present, the molecules of the toxins will bind to the antibodies in the Enzyme Conjugate.
• Once incubation period is over, an aliquot of the sample is added onto the sample ports and incubated for another 5mins at RT. This time, the toxin-enzyme conjugate is separated from any particulate matter as it seeps through the membrane to the Test and Control reaction Ports.
• The toxin-conjugate complexes are captured in the Test port by immobolized anti-toxin. Then, the Wash Reagent, which is also a buffered similar to the Sample Diluent, is added to both ports. The reaction ports are then incubated again for 5 mins. At this point in time, the enzyme (HRP) modifies the Substrates Reagent, causing a colour change.
• The test kit is then read visually after incubation. The Control Port should be blue in colour while the Test Port with a blue colouration indicates presence of Toxins.

Test Results:
As this is not a quantitative test, there are no reference ranges. Test results will only indicate the presence of absence of Toxins A&B of C. difficile.

A positive result is indicated by a blue colouration in 2 Reaction Ports. A blue colouration in the Control Reaction Port (upper left) means that the sample has been added, reagents were active at the time of use and that proper sample migration has occurred.

If there is only blue colouration on the Control Reaction Port (upper left) and the Test Reaction Port (upper right) is colourless, then this would be a negative result.

Clinical interpretation:
As mentioned this test is to determine the presence of Toxins A&B of Clostridium difficile in human stool. It is part of a test called Stool Occult test. This test is used to aid physicians in diagnosing C. difficile-related diseases.

Alrighty, I'm done =). We've got 10 weeks more to goooooooo! Have fun all!

The cutest Lab Freak,
Sharifah