Various Cultures

Urine Culture
(Culture on Blood Agar and MacConkey agar)

This test is performed when a patient is suspected to have UTI ( Urinary tract infection )

Basically, when there is growth of pure culture in high colony counts and the urinalysis resulted in large amount of bacteria, we will consider it as positive result for urine culture. 

Methodology:

1. Use a smaller loop to obtain the urine sample
2. Draw a vertical line at first in order to distribute the sample evenly.
3. Then streak the plate starting with close distance to far distance between each horizontal line.

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Blood Culture(Culture on Blood Agar and MacConkey agar)
This test is performed to determine and identify the presence of fungi, bacteria or virus in the sample. It is ordered when the patient shows the symptom of sepsis.

*Normally, the FBC( Full Blood Count ) test will also be ordered along to determine whether the patient have increased WBC (White blood cell ) that indicating a potential infection.*

 Methodology:
1.

Scan the bar code.

2.

Insert the culture bottle into the appropriate position.

3.

Wait 2 days for the analyzer to detect whether there is any bacteria growth inside the culture bottle.

*Basically, there should be no bacteria inside the human blood as it should be sterile inside the body.*

4. If there is bacteria inside the culture bottle, a syringe will used to withdraw the patient's blood from the rubber sealed bottle and one drop of blood is used for culture.

Lancefield Grouping test :

-- a test that used to identify the species of detected Streptococcus.

Reagent used.

There are total 6 types of Streptococus : A, B, C, D, F, G .
The agglutination indicate that which the detected species belongs to. 

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Swab Culture
(Culture on Blood Agar and MacConkey agar)

1. If the culture consists of bacteria growth followed by beta-haemolysis, the microorganism is suspected to be the Streptococcus aureus.

   

   β-hemolysis is the lysis of red blood cell in the blood agar around the colonies due to the streptolysin which produced by the bacteria.

   
   
2. Catalase test will be conducted.
   
   Small amount of the suspected organism will mix with a drop of catalase which placed on a slide. Bubble formation indicating positive result.
3. Then, Coagulase test will be carry out.
   
   Small amount of the suspected organism will mix with the plasma (FFP) within a test tube.
   If there is coagulation of the plasma indicating positive result.
4. Gram staining and sensitivity test will take place afterward.

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Stool Culture(Culture on  MacConkey agar and XLD agar)

1. Small amount of the patient's stool is added into a test tube containing Selenite F solution and incubate for 1 day.
2. While in the same first day, the stool is also used to culture on MacConkey agar.
3. In the second day, the incubated Selenite-F solution is cultured on XLD agar plate.  

Positive result: Black colonies ( Salmonella ) present on XLD agar.
* The microbe will change the color of the agar*

Culture the "Black colonies" on TSI agar ( Triple Sugar Iron agar ).

 

(Left) Agar turned black indicating positive result with the presence of Salmonella.

(Right) Agar remained yellow in color indicating negative result.

Procedure of culturing on TSI:

1. Stab vertically into the slant agar.
2. Then, drag the loop out and streak a vertical line on the agar surface.
3. Lastly, do the horizontal streaking.

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Other culture

Upper respiratory sample( Sputum , throat swab...） ，Eye swab , high vagina swab...  use Blood agar, MacConkey agar and Chocolate agar.

Chocolate agar is placed in a sealed tin with lighted candle while incubating in order to create an anaerobic environment.

Other than Blood agar and MacConkey agar, urethral swab is also cultured on the Sabaraud agar to find out any yeast presented.