Medical Microbiology - Streptex Test

Hi, there! Muna here XD

SIP is finally over. 5 months of hard work, blood (literally!), sweat and tears.

Good luck to all for the MP project reports.

Streptex is a rapid latex test used to determine the Lancefield grouping of streptococci. This test uses the principle of antigen-antibody binding. The antigen-antibody complex forms as a visible precipitate in a positive reaction.

Most of the Streptococcus sp. contain group-specific antigen. These antigens are actually carbohydrate structural components of the bacterial cell wall. It was shown by Lancefield that these antigens can be extracted in a soluble form and tested using precipitation reactions with homologous antisera.

In Streptex, the antigen extract is obtained using a simple enzyme extraction procedure. Polystyrene latex coated particles coated with group-specific antibodies are used to identify the antigen in the extract. Agglutination will occur strongly in the presence of the specific homologous antigen and remain smooth or milky in its absence.

The latex reagent contains a combination of fibrinogen, IgG and anti-capsular monoclonal antibodies to allow recognition of capsular polysaccharides of Staphylococcus aureus.



5 pure growth colonies of Streptococcus sp. are used to make a 0.5 McFarland suspension in 400ml of Extraction Enzyme.
Incubate at 35oC between 10 mins and 1 hour.
Re-suspend the test kit latex by shaking.
Add 1 drop of each test kit latex (A, B, C, D, F, G) to the test circles on the reaction card.
Add 1 drop of extracted sample to each test circle.
Rock card horizontally or use a disposable rod to mix for 1 minute.
Read the result immediately after 1 minute of shaking.

Positive
Visible clumps
Negative
No clumping/agglutination
Milky appearance

The main use of this test is to test for the more virulent beta-haemolytic strains of Streptococcus.


*Colonies should be taken from Blood Agar Plates (BAP), Chocolate Agar (CHOC) or CAN (Columbia agar) and not be more than 48 hours of growth.

References:
Taken from
http://www.remelinc.com/Clinical/DiagnosticTests/Streptex.aspx
http://www.dcss.cs.amedd.army.mil/field/FLIP%20Disk%2041/.\Documents\M403_Micro_Aug\Streptex.DOC
on 21 Sep 2009

Muna

0703791D

Pathogens found in stool.

Two out of all the organisms found in stools which are pathogens to our body are Vibrio cholerae and Campylobacter jejuni

Vibrio cholerae
Vibrio cholerae species belong to the gram-negative bacteria group. It is a facultative anaerobie and curved rod in shape. It is motile and moves by its single flagella. Vibrio cholerae is also identified by being oxidase positive and does not produce hydrogen sulfide and gas Kliger Iron agar.
Vibrio cholerae can be found water surface in many parts of the world.

Below shows a picture of Vibrio cholerae species.


Pathogenicity
Vibrio cholerae causes Cholera in humans. It is an acute intestinal infection and is transmitted to human through contaminated water and food, or through uncooked food such as shellfish and other seafood.
One of the symptoms that people with cholera have is diarrhea. It is caused by a toxin produced by the organism which targets our epithelial cells and that explains for the watery stool appearance in patients infected by Cholera.




Campylobacter jejuni

Campylobacter jejuni is a gram negative, spiral shaped and motile organism.It is a microaerophilic organism therefore, it cannot survive in an environment with high level of oxygen. This organism is usually in found in poultry and contaminated water or sometimes even unpasteurized milk.

Below shows a picture of a Campylobactor jejuni species.



Pathogenesis
The name of the infection caused by this organism is called Camphylobactoriosis. People who are infected by this bacterium have symptoms such as: bloodly, watery or sticky stool. Some people may experience headache, muscle pain and nausea.


So sorry that i forgot to indicate who i was. This is Jennifer here