Food E.coli Bacteria Detection-counting MPN Method

- Sep 18, 2019-

Our eco-sansa E.Coli Indicator Bacteria Test Kit can used MPN method: using the selectivity of the special physiological function of microbes under test to get rid of the interference of other microbial groups, and through the physiological function to judge the performance of the existence of the groups of microorganisms belong to spend. Because the distribution of bacteria in the sample is random, so the detection of bacteria, probability theory can be used to calculate number of bacteria, the experimental results expressed in MPN value, but values MPN is not said the actual number of colonies, the actual number of colonies are likely to fall within the confidence interval, any one of the MPN values fall within the confidence interval probability is one of the biggest point.




For example: dilution degrees of 0.01, 0.001, 0.0001 of the positive number 2-0-0 respectively;




Check the MPN retrieval table shows:




MPN value is 92 CFU/ml (g), when the confidence level of 95%, is the lower limit and upper limit of 14380 respectively, namely the corresponding colony concentration range is 14 ~ 380 CFU/ml (g), it means: the test results show that the concentration of bacteria in 14-380 CFU/ml (g) interval could, just 92 CFU/ml (g) the most probability to appear probability is 31.9%.




Food e. coli bacteria detection, the plate count method



Compared with the MPN counting method, plate count method is more suitable for higher levels of fecal coliform in the food. But the fecal coliform is how much content is higher? No clear provisions in the national standard, but usually think product coliform group with 100 cfu/g (mL) is bounded, generally considered to be more than the content content is higher. But exactly when choosing tablet counting method of e. coli bacteria detection, mostly still depends on the standard of your products. If the unit of product standard coliform bacteria content of CFU/g (mL), it must choose plate count method. If (mL) or MPN / 100 g/g (mL), you should choose the MPN counting method and MPN method to choose which version of national standard here is no longer here. Therefore, according to their own product to choose the appropriate test methods.




E. coli plate count method steps are as follows:




1, preparation of sample diluent, draw 1 ml join the tablet, pouring and sterilized 55 degrees VRBA AGAR 15 to 20 ml, 36 degrees for up to 24 hours after solidification, counting purple colonies


2, then appropriate dilution degrees VRBA tablet on the purple colonies through 10 BGLB, positive rate of statistics


3, then count the VRBA results positive rate of X X dilution degrees, is the final result.