Lab positive controls

Hi, I have just taken over management of a small food micro lab with very basic procedures. We test for salmonella, E coli, Coliforms, S aureus and of course TVC. I need to put positive and negative controls in place and have chosen and ordered the relevant organisms.  They come in form of a freeze dried disc.

 

Please can anyone give me some help and advice on how to culture and grow the micro-organisms - what media would you recommend?   they will be used for media quality control and for process control.

 

Thank you

Dear kehlan,

 

Never had the funding to utilise this highly desirable option but I would expect (demand?) the supplier to provide all the details you mention ??

 

Rgds / Charles.C

you'd think so.  The organisms come in form of a frozen disc. Instructions tell you to place the disc on a suitable medium and incubate. I know for solid media the last lab i worked in used sheep's blood which is simple enough.  but they also produced cultures in liquid form for use in process control... for example, adding to BPW for positive control for salmonella testing. 

 

The annoying thing is, a couple of years ago I had access to all this information when I worked as a senior technician, but when I left there, I never thought I would go back to lab work... now I've ended up as a lab manager and am trying to remember all that stuff.  I'll probably havve alot of questions ctually as we are trying to bring the lab up to the standards required for accreditation and we have a long way to go to acheive that goal.

Why don't you get your culture rep in. 3M & Neogen will help you decide on your controls. that's what their there for!

Caz x

Thanks.  I was just hoping that if any other microbiologists use this forum, they might be willing to share some hints and tips as to what they consider the best way to do it.

Thanks.  I was just hoping that if any other microbiologists use this forum, they might be willing to share some hints and tips as to what they consider the best way to do it.

Dear Kehlan,

 

yes, certainly worth a try. There must be a few (other) rich lab. people here. :smile:

 

I did do a quick net search but disc-type formats seem relatively little discussed.

 

you might find this of interest although it seems to use a non-disc system -

ATCC_Bacterial_Culture_Guide.pdf   1.24MB   44 downloads

 

Maybe you could name the product / brand ??

 

Rgds / Charles.C

Kehlan you can use TSA triptic soy agar. I am sure you have to hydrate the disk in some form and I would expect he disk to have a bulb that you would break to hydrate it.

You would then streak it out on the plate. The plate has a shelf life, typically it is 7 days. Then you would select a colony and streak that out to a new plate for an additional 7 days. This can go on four about 4 months.

All of this is just a short quick explained procedure but the manufacturer of the disk will tell you exactly what to do and what to use. If I can help you further let me know.

Best.

If you want to list the bacteria you have I should be able to advise on what medium to use.

Another alternative is to use the webpage of ATCC, NCTC, DSM or any of the big culture collections, search for the strain you are using and they will generally recommend a resuscitation/growth medium and temperature.