Listeria swabbing
Not sure if I am writing in the correct forum.
We use a 'trans swab' for listeria environmental monitoring.
A colour change indicates listeria (species) but occasionally we have had a colour change and then swabs we send in to the external lab are negative.
One of our issues we have with the transwab is that the external lab can't and won't do an confirmation of the actual swab (trans swab) we take that has changed colour.
Is there someone in here that has a lot of experience with these trans swabs and how to handle a presumptive positive?
They are a really cheap alternative to external testing but...
Hope it is well worded enough, otherwise let me know!
Also let me know if GFSI auditors tend to accept trans swab as an acceptable method.
Thanks
hi
greeting for the day !
as per understanding of your statement , i would like to say that procedure of sending tans swabs after incubation time period to external lab shall not be a right way for listeria/ any microbiological test.
In these cases, the potential causes of “False Positive” tests are organisms of faecal origin, which is most commonly a challenge with any pathogen indicator test
further , you must check with manufacturer's guideline for effectively procedure to be followed for trans swabs testing for listeria, also need to check swab taking and testing procedure by your technician/ testing person
Principle & methodology against the swab and external lab test is different , but you have to take validation report from trans swabs supplier for acceptability of trans swabs that would be acceptable by any external GFSI auditor but you have to validate your listeria testing by external labs as well .
in my current organization, we using listeria indication swabs stick as indicator test as per schedule and risk based frequency. & external lab testing on quarter basis to ensure Environmental monitoring as per standards requirements
hi AJL ;)
I believe we are talking here about two situations :
- verification (trans swabs) / Verification is proving that it is working
- validation (lab swabs) / Validation proving that it will work
It seems that you are controlling your environment by pre-requisite (BRC issue 9 - 2.7.4) , hence why you need to validate your procedure before introduction.
This is associated with cleaning regime and again with cleaning validation (BRC issue 9 - 4.11.2). Validation must be fully documented (scientific/technical literature, laboratory tests, pH tests etc). In this case you must validate your cleaning procedures by laboratory testing and then when successful you can introduce your verification (trans swabs, ATP swabs etc).
Trans swabs can be used as long as you have your validation documents, but you need to have a good corrective actions for presumptive (colour change).
Corrective actions shall include :
- cleaning and post trans swabs test and root cause investigation plus preventative actions (hygiene team briefing or cleaning procedure review)
- cleaning and lab testing, in case of repetitive Listeria presumptive from the same point
- cleaning and equipment inspection (surface is not suitable for cleaning etc) however this should be considered in your validation exercise
;)
What we have been able to do in the past is send the trans swab in to an external lab and get it 'confirmed' that is they test to see if it is actually listeria growing.
However labs won't do this anymore.
We have had a period where a lot of the swabs change colour, but then when we send in swabs to an external lab we have negative so of course we suspect that we have a case of false positives.
What causes the false positives, is it just dumb of me to swab during production? Are they only really suitable for swabbing non cleaned equipment??
I have always read that environmental monitoring should occur during production so you can see the problem here!
The test has its own validation from the supplier already conducted.
I think the idea of doing external quarterly sounds good. ☺️