Most probable number MPN.pptx

MPN is most commonly applied for quality testing of water, i.e., to ensure whether the water is safe or not in terms of the bacteria present in it. The presence of very few faecal coliform bacteria indicates that the water is likely free of disease-causing organisms.
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1. Most probable number (MPN) Technique DEBORAH A R

2. Agenda MPN TECHNIQUE 2 water MOST PROBABLE NUMBER PRINCIPLE MATERIAL REQUIRED PRESUMPTIVE TEST CONFIRMATIVE TEST COMPLETE TEST

3. WATER MPN TECHNIQUE 3 Water is an essential part of life. There are thousands of microorganisms that live in water and are transported through it. People are affected due to bacterial infectious diseases transmitted through contaminated water (e g: cholera, typhoid fever, and bacillary dysentery). Coliform bacteria ( Escherichia coli ) strain is the indicator organism used to indicate faecal contamination and water analysis is mainly based on the concept of faecal indicator bacteria.

4. Most Probable Number Most Probable Number (MPN)  is a method used to check the water. MPN is most commonly applied for quality testing of water. In drinking water, the presence of very few faecal coliform bacteria would indicate that water probably contains no disease-causing organisms. While the presence of large numbers of faecal coliform bacteria would indicate a very high probability that the water could contain disease-producing organisms making the water unsafe for consumption. 4 MPN TECHNIQUE

5. Principle The most probable number (MPN) is a statistical method. The coliform groups comprise all aerobic and cultivating anaerobic bacteria. Coliform bacterial densities can be determined by either the Multiple tube fermentation technique (MPN Test). The Multiple tube fermentation technique providing the Most portable number (MPN) is an Indirect count technique relying on statistical interpretation of growth. The test was conducted in three steps Presumptive test, Confirmatory test, and Complete test . 5 MPN TECHNIQUE

6. Materials Required Brilliant Green Lactose Broth Eosin Methylene Blue (EMB) agar Gram staining kit Erlenmeyer flask Pipettes Test tubes Durham’s tube Petri dishes Other lab wares 6 MPN TECHNIQUE

7. Presumptive test - procedure Distribute 10 ml Single strength lactose broth (SSLB) each to 10 test tubes and Double distilled strength Lactose broth (DSLB) to 5 test tubes. Add the Durham's tube in inverted position and sterile them at a time. After autoclave, Inoculate the 0.1 ml of water sample to each 5 tubes of SSLB, 1 ml of water sample to each 5 tubes of SSLB tubes and 10 ml of water sample in 5 tubes of DSLB correspondingly.  Incubate the tubes at 37 °C and examine the gas formation in Durham’s tubes at 24 hours (positive test) or not 48 hours (doubt full tests) proceed to confirmed.   Compare the number of tubes giving positive reaction to a standard chart and record the number of bacteria present in it. 7 MPN TECHNIQUE

8. 8 MPN TECHNIQUE For example,  A water sample tested shows a result of 4 –2–0 (4× 10 ml positive, 2 × 1 ml positive, 0 × 0.1 ml positive) giving an MPN value is 22 , i.e. the water sample contains an estimated 22 C oliforms per 100 ml.

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11. Confirmative test - Procedure Take a loopful culture from the Lactose broth tube from the highest dilution that still showed a positive test and streaks it on the EMB agar plate. Incubate the plates at 37 °C for 24 hours. Observe the typical Escherichia coli colonies showing a greenish metallic sheen. 11 MPN TECHNIQUE

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13. Complete test Pick up a suspicious colony ( Escherichia coli ) from EMB agar plate, make a smear and conduct Gram staining. 13 MPN TECHNIQUE

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