C & S test

Culture and Sensitivity test

• The specimen is cultured on agar plate to identify the microorganism that present in the sample based on the culture's morphology, biochemistry profile and staining.
• The specimen is cultured on a specific antibiotic-containing agar plate to discover the microorganism based on its susceptibility.
  Also, it helps in determining what type of antibiotic can be given to the patient for infection treatment.
• This test can be done with different types of body fluids and excretion, such as urine, blood, pus, swab, saliva, mucus, stool and so on.

Procedure:

Culture and species determination :

 

1. Insert 4 full amount of normal saline into the test tube ( "Culture tube" )
2. Take little amount of bacteria from the pure culture and insert into the tube until the saline looks slightly turbid.
   
   
3. Incubate at 37°C for 2 hours.
4. Insert 100µl of the culture into each well of the Microgen kit ( contains certain addictive and reagent for growing ) to determine the species of the microorganism.
5. Add 2 drops of mineral solution.
6. Seal the kit and incubate for 1 day.
7. Add appropriate drops of reagent in to specific well.
8. Compare the resulted color with the identification system chart, calculate the number and key in to the computer software to determine the species automatically.
   
   

   

   Microgen kit which added with sample and reagent in each well.

Identification system for Streptococci and Enterococci .

Identification system for all Enterobacteriaceae and excessive range of oxidase-positive Gram-negative bacilli.

Fill in the blank and calculate the number.

Key in details into the computer software.

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Antibiotic Susceptibility Test:

1. Add 0.5ml of peptone water into a microcentrifuge tube ("Sensitivity tube" )
   
   
2. Take little amount of bacteria from the pure culture and insert into the tube until the peptone water looks slightly turbid.
   
   
3. Incubate at 37°C for 2 hours.
4. Dip a clean cotton swab into the sensitivity tube and fully spread the solution on the agar plate ( Müeller-Hinton agar ).
5. Add on the antibiotic chips with the appropriate distance ( about 2.4 cm) based on the species.
   For example, Escherichia coli

   

   For E.coli, there are 12 antibiotic chips to be tested.

   
   
6. Incubate the agar plate for 1 day.

The microbes are resistant to the AMS 20 while sensitive to the other antibiotics.

Result Interpretation:

*Often correlate with other relevant test result before the final result is reported*

For example,
FBC result :

• High lymphocytes indicate viral infection, thus no bacteria will grow on the culture plate. 
• High neutrophils indicate bacteria infection, thus there should be bacteria growth on the agar.

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Reference:

1. http://antranik.org/culture-and-sensitivity-test-the-clinical-requisition/
2. https://labtestsonline.org/understanding/analytes/urine-culture/tab/test/