6 replies to this topic

[anna898]

HI

I need a bit of an advice . I cant understand how it is possible to have one confirmed Listeria spp result.  4 samples from the same batch  have been sent to the lab and only one come back positive, how is it possible??? 

All environmental swabs negative as well.

RTE chilled product.

It cannot be one of ingredient as  the whole batch would be positive not just one sample, or I'm wrong??

 

 

 

[Scampi]

You are incorrect

 

Because you're not able to take (or didn't take) a fully homogeneous  sample, you've likely hit a spot where listeria was present and there others were negative

 

do not disregard this positive hit. you need to sample this lot again, heavily.  Then, and only then, can you release the lot and be confident what you received was a false positive  (but not very likely this is the case)

[olenazh]

Did you do the re-test for that particular sample? It could be presumptive positive, I've experienced that. Meanwhile, send another composite sample of the same batch for Listeria spp. 

[G M]

HI

I need a bit of an advice . I cant understand how it is possible to have one confirmed Listeria spp result.  4 samples from the same batch  have been sent to the lab and only one come back positive, how is it possible??? ...

It cannot be one of ingredient as  the whole batch would be positive not just one sample, or I'm wrong??

 

Even though we don't know what kind of product you're talking about, it is unlikely that your material is 100% homogenous.    Even a fluid can have contamination present in one portion of a vessel/flow and not another.

[Miss Frankie]

It's entirely possible!
We went thru about 2 weeks earlier this summer where we were finding listeria in every 3rd or 4th batch of the same product for a couple weeks.
We ramped up swabbing and found nothing.  We shut down production for a day and did a deep clean.

Finally determined that someone wasn't sanitizing bags of product if they were being fed back to the line.  Once we put a procedure in place to fully sanitize every bag before it was reopened, the problem stopped.

[Tony-C]

Hi anna898,

 

I wouldn’t panic based on 1 positive result, it may have been a contaminated sample.

 

Arrange for another set of samples from that batch at an increased sample rate asap.

 

Repeat your environmental swabs and take more swabs from food contact surfaces on the line in question.

 

I assume that you sample periodically, say monthly, so arrange for additional batches to be sampled as well.

 

Kind regards,

 

Tony

Edited by Tony-C, 10 September 2022 - 04:09 AM.

[EagleEye]

It is entirely possible as there is no thumb rule for the microbial world how to behave. Listeria is notorious to survive in these scenarios, sometimes negligible limiting factors might have come in its favor.  

From the source of the product it could have contaminated that portion. Explore every possibility.