Microbial counting

I will dilution for microbiology testing but sometimes during reading of plate, i encounter that plate

10^1: has no growth

10^2 : has 10 colonies (for an example)

how should i read the result? should i assume 10^1 has no growth or TNTC?

Thank you.

Hi Tharsh06,

:welcome:

Welcome to the IFSQN forums.

Ideally you need 30-300 cfu on a plate to get an accurate reading. Your readings don’t make sense as 10^1 should have had a count around 100 cfu/ml or g which is not uncountable. I would repeat the tests.

You might find this useful: Introduction to Enumeration of Bacteria - North Carolina State University

Kind regards,

Tony

I'd recommend when starting an unfamiliar matrix or new product to run your sample(s) in triplicate (if possible). I find that having that initial study where my range is much more broad helps me adjust with future versions of the sample. 

Also, is this Petrifilm or a traditional plating media? I have found that this scenario happens a lot more with petrifilm than traditional plating methods. Hope this helps :)

I'd definitely rerun the sample, as Tony suggested! 

Hai Mr Tony, 

Noted on this. I will rerun the testing.

Hai Mr Austin, 

this issue encountered in traditional plating method. 

I will run my samples in triplicate to observe the result. 

Thank you.