E. coli MPN refers to the E. coli Most Probable Number, which uses a specific technique to estimate the concentration of E. coli bacteria in a sample.
Understanding the Most Probable Number (MPN) Technique
The Most Probable Number (MPN) technique is employed to estimate the number of bacteria in a food or water sample. This is achieved by culturing replicate portions of the sample to identify the presence or absence of the target microorganism (E. coli, in this case) in each portion.
How MPN Works
The MPN technique involves several steps:
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Serial Dilutions: The original sample is serially diluted.
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Inoculation: Multiple replicates of different dilutions are inoculated into a suitable growth medium.
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Incubation: The inoculated tubes or wells are incubated under specific conditions conducive to the growth of E. coli.
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Observation: After incubation, each tube or well is observed for growth (typically indicated by turbidity or a color change, depending on the medium).
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Statistical Estimation: The pattern of positive (growth) and negative (no growth) results is then compared to standard statistical tables or formulas to estimate the MPN of E. coli in the original sample. The MPN is usually expressed as MPN per unit volume (e.g., MPN/100 mL).
Application to E. coli
When the MPN technique is used specifically for E. coli, selective media are used to ensure that only E. coli or closely related coliform bacteria grow. This enhances the specificity of the test.
