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Salmonella testing in swabs


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#1 Janie

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Posted 29 March 2018 - 11:06 AM

Hi everybody.

I am inquiring your help considering the pt scheme for salmonella testing in swabs. In our lab, for this type of analysis we are using standard SRPS EN ISO 6579:2008. And while we are awaiting our test sample, we got a preliminary instruction from LGC about the preparation of the sample, and it states that after swabbing the inoculated the plate and placing the swab into primer diluent (buffered peptone water), we should take 5ml of it, and add it to the enrichment broth ( RVS). Well, the instruction did not say what should be the volume of the RVS. By are standard, we add 0,1 ml of the sample to 10 ml of RVS. And following that logic, then we should add 5 ml to 500 ml. Is not that a little bit too much possibly? Maybe then the sample will be too diluted? This is our first time that we are doing pt schemes for swabs, and any help will be welcomed :)

 

Thanks in advance 



#2 FurFarmandFork

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Posted 29 March 2018 - 01:30 PM

Your enrichment broth is going to be presumably incubated so that the cells you inoculate into it will proliferate, the volume transferred generally isn't much (as you notedin your standard procedure).

 

Just call LGC and see what they want for final volume of enrichment media. No sense messing with their instructions, needless liability.


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#3 Janie

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Posted 30 March 2018 - 11:09 AM

Your enrichment broth is going to be presumably incubated so that the cells you inoculate into it will proliferate, the volume transferred generally isn't much (as you notedin your standard procedure).

 

Just call LGC and see what they want for final volume of enrichment media. No sense messing with their instructions, needless liability.

That is a great advice actually, thank you so much for your quick response.

Best regards.



#4 Charles.C

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Posted 30 March 2018 - 12:58 PM

Hi Janie,

 

Out of curiosity, what is LGC ?

 

Can offer a  little information -

 

It is important that the inoculum size used for enrichment culture in RV Broth is sufficiently small not to interfere with its selectivity. Inoculum/broth ratios 1:100 to 1:2000 have been suggested.

Attached File  CM0669, Rappaport-Vassiliadis (RV) Enrichment Broth.htm   23.71KB   6 downloads

 

Attached File  Isolation of Salmonellas.pdf   1.63MB   12 downloads

 

I agree with 3F's suggestion.


Kind Regards,

 

Charles.C


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#5 Janie

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Posted 30 March 2018 - 03:19 PM

Hi Janie,

 

Out of curiosity, what is LGC ?

 

Can offer a  little information -

 

attachicon.gif CM0669, Rappaport-Vassiliadis (RV) Enrichment Broth.htm

 

attachicon.gif Isolation of Salmonellas.pdf

 

I agree with 3F's suggestion.

It stands for LGC standards, we ordered our pt scheme from them. My whole lab, including all departmants usually orders all the pt schemes for lgc or from fapas, because Customs let the test samples get in the country without too many hiccups :) I think that most of the labs in Serbia order pt scheme from them, for the same reasons.

Thank you so much for additional documentation, I will read it thoroughly.

Best regards,

Janie



#6 Scampi

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Posted 06 April 2018 - 02:32 PM

when i've run salmonella in the past, the solution was tested at

1:1

1:10

1:100

1:1000 

dilutions for accuracy 


Because we always have is never an appropriate response!





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