CFU Calculation

Microbiology
#1

First, i did serial dilution and plated them. e.g., for e.coli, I found that the plates came as TNTC from 10-1 to 10-5 , but 10-6 . 10-7 and 10-8 came as 628, 211 and 98 respectively. i chose 10-7(211), so it comes to 2.11 x 10^9 cfu/ml. from here, how do i dilute the suspension to get 1 X 10^6 cfu/ml? Plz answer.

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#2

Hi, It’s not possible, you already got 628 in 10-6 dilution you can’t decrease dilutions… Check with the COA of culture You have taken. If it’s 1*10-6 … then the problem is with serial dilution. Another thing how you are considering Tntc. Above 100 itself tntc. you are only getting count in 10-8. Which is 98.