1 reply to this topic

[butter1983]

I'm new in the micro lab and still learn. I took over after person did not show up at work. Before I was in production.I have diploma in Quality Lab.

Once a week I go to factory (we produce bechamel sauce) to do a swab from equipment. I use 3M Quick Swab (swab containing Letheen neutralizing buffer 1ml). I take swab roughly 10x10cm.

After I pour the buffer into Petrifilm. Can you please advise how to count colony. If 10 colony then result 10?

 

Second is Air Sampling. I go to chosen room or chiller and I expose APC and Y&M Petrifilm for around 5 min. Then incubate.

How to calculate the colony that grow?

 

Thank you so much for help.

Adam

[Charles.C]

I'm new in the micro lab and still learn. I took over after person did not show up at work. Before I was in production.I have diploma in Quality Lab.

Once a week I go to factory (we produce bechamel sauce) to do a swab from equipment. I use 3M Quick Swab (swab containing Letheen neutralizing buffer 1ml). I take swab roughly 10x10cm.

(a) After I pour the buffer into Petrifilm. Can you please advise how to count colony. If 10 colony then result 10?

 

(b) Second is Air Sampling. I go to chosen room or chiller and I expose APC and Y&M Petrifilm for around 5 min. Then incubate.

How to calculate the colony that grow?

 

Thank you so much for help.

Adam

Hi Adam,

 

I assume you mean how to express the count from plate.

 

Answers's units should relate to yr target values for the measurements. Do you have any ?

 

Detailed procedures can vary with system. I'm not familiar with precise 3M method.

 

(a) I assume you use 1ml on 3M plate

If petrifilm count is X colonies, count/cm2 of equipment = V/A where -

V = total liquid volume in ml from which the 1ml sample for petrifilm was taken

A = equipment area in cm² which was sampled

 

eg swab immersed in 200ml solution, area = 100cm², petrifilm = 1ml/10cfu,

 

count = 200/100 = 2cfu/cm²  

 

(b) Count/unit area/unit time = cfu/area of petrifilm surface/time exposure

Units depend on yr standard and can vary, for example area in cm2 and time in hours

 

PS (added)- I enclose brochure for 3M swab sampling procedures. This describes 3 possible methods and the calculation methods are included. My text above matches the procedure/calculation for the middle method. As illustrated, you can easily adjust yr calculation if using the 1st or 3rd method.

 3M, Petrifilm Enviro.Monitor.Procedures.pdf   1.02MB   30 downloads

Edited by Charles.C, 17 November 2021 - 05:02 PM.
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