Hygiene Swab and Air Sampling
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
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 24 downloads