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2 Listeria species detected in Lot. Possible ?


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miniaczka90

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Posted 26 April 2019 - 12:06 AM

Hey guys

I am wondering- we have done some testing,
Same lot number two different listeria . One is mono . One is spp
How possible is that



Charles.C

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Posted 26 April 2019 - 01:44 AM

Hey guys

I am wondering- we have done some testing,
Same lot number two different listeria . One is mono . One is spp
How possible is that

 

What specific test (or tests) was applied ?


Kind Regards,

 

Charles.C


miniaczka90

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Posted 26 April 2019 - 02:06 AM

Just regular, first VIDAS for 125g , and the same batch coming out with mono one with spp



Charles.C

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Posted 26 April 2019 - 02:26 AM

Just regular, first VIDAS for 125g , and the same batch coming out with mono one with spp

 

Which VIDAS, there are several ? eg LDUO ?


Kind Regards,

 

Charles.C


Charles.C

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Posted 26 April 2019 - 03:12 AM

Which VIDAS, there are several ? eg LDUO ?

 

I Assume the test qualitatively confirms both Listeria spp and/or L.monocytogenes.

 

I assume two tests were made, Unit Packaging weight = ? Total Quantity = ? sample size/sampling method =?.

 

The result proves that the 2 quoted species exist in the lot.

 

Possibility Yes.

Probability estimate of Percentage contamination requires sampling information. 95% Confidence Range will probably  be wide.

 

What specifically did you want to know ?


Kind Regards,

 

Charles.C


zanorias

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Posted 26 April 2019 - 05:27 AM

I've seen a lab cert positive for listeria (ELISA) in which two species were detected (innocua & seeligeeri). Mono was negative.



miniaczka90

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Posted 26 April 2019 - 12:01 PM

okay , thank you guys .

But how is that possible ?

Example: we are running whipping cream, one of the tub time : 13:00 tested positive for listeria seeligeri , and another tub with the cream collected from the line 13:03 has listeria Mono .

How possible is that . The samples have been tested for 125 g .



zanorias

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Posted 26 April 2019 - 12:26 PM

I'm no microbiologist but I don't see why it wouldn't be possible for two species to contaminate a product from two origins, perhaps two different sources of contamination or an event between the sampling times. Potential contamination from the sampling equipment/process itself? Or perhaps a false positive (but don't assume that).

Out of curiosity where are you based and the product is RTE?



Charles.C

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Posted 26 April 2019 - 01:56 PM

okay , thank you guys .

But how is that possible ?

Example: we are running whipping cream, one of the tub time : 13:00 tested positive for listeria seeligeri , and another tub with the cream collected from the line 13:03 has listeria Mono .

How possible is that . The samples have been tested for 125 g .

 

JFI, this is a 1993 quote -

 

Three hundred samples of pastry from 100 different suppliers in western France, including butter-cream, whipped dairy cream and custard filled cakes from each supplier, were collected and tested for the occurence of Listeria spp. in 25 g samples.

.

Listeria spp. were detected in 21.7% of the samples: Listeria monocytogenes in 13.7%, Listeria innocua in 10% and Listeria seeligeri in 2.3%.

Thirteen samples were contaminated with two species simultaneously.

The frequency of contaminated samples was not related to the composition of the pastry filling used, but it seemed to increase with the number of aerobic contaminant microorganisms in the dairy cream-based samples.

The contamination rate was dependent on the place of manufacture.

 

The numbers of Listeria spp. and Listeria monocytogenes were estimated on positive samples at the 25 g level as follows: < 0.3/g, Listeria spp. in 47 samples, L. monocytogenes in 27; 0.3–30/g, Listeria spp. in 13, L. monocytogenes in nine; 30–300/g, L, monocytogenes in one; 300–3000/g; L. monocytogenes in three; 700 000/g, L. monocytogenes in one

 

 

 

Also see this -

 

Attached File  Diversity of Listeria Species in Urban and Natural Environments,2012.pdf   1.39MB   13 downloads

 

Do you have an EMP running for Listeria ?

 

 

PS - Probably not relevant to yr situation but I also noticed this summary comment in a Greek (2015) survey -

 

Out  of  all  food  categories  examined,  the  presence  of L.monocytogenes  was the highest in desserts with dairy cream and ice cream (22.7% and 26%, respectively), both of which are predominantly made with whipped cream or with pastry cream both of which involve much  handling  throughout  the  final  formulation  process. 

 

Another factor  is  the  omnipresence  of  uncooked  eggs  throughout  kitchen working stations since the pasteurized liquid/powdered egg option is not favored. This fact, escalated by the occasional addition of raw eggs in  the  final  preparatory  stages,  leads  to  cross-contamination  of  RTE desserts  and  ice  cream.

Kotzekidou  [13]  reported  a  high  prevalence rate of 20% in desserts with dairy cream and a 17.7% in desserts [27] in studies in Northern Greece.

 

Attached File  L.mono and Salmonella spp in RTE Foods,2015.pdf   437.01KB   15 downloads


Edited by Charles.C, 26 April 2019 - 02:24 PM.
expanded

Kind Regards,

 

Charles.C


Marshenko

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Posted 26 April 2019 - 02:34 PM

I don't understand the question.  Since L.mono is a species of Listeria, anything containing L.mono will also "test positive" for Listeria spp. 100% of the time.  Sounds like they just ran a genus and then a mono test, which isn't uncommon.  You test for genus first, and if it is positive, then you speciate it out or test for specific pathogens of concern.


Edited by Marshenko, 26 April 2019 - 02:35 PM.


Charles.C

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Posted 26 April 2019 - 02:41 PM

I don't understand the question.  Since L.mono is a species of Listeria, anything containing L.mono will also "test positive" for Listeria spp. 100% of the time.  Sounds like they just ran a genus and then a mono test, which isn't uncommon.  You test for genus first, and if it is positive, then you speciate it out or test for specific pathogens of concern.

 

Note the L.seeligeri. This will take some effort. (not a human pathogen of course).

 

Nonetheless, I also do not find it  particularly amazing to see more than one L.X species potentially in an environment. I wonder how they distinguish them in the lab.


Edited by Charles.C, 28 April 2019 - 03:51 AM.
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Kind Regards,

 

Charles.C


Marshenko

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Posted 26 April 2019 - 02:49 PM

Note the L.seeligeri. This will take some effort.

 

Certainly not unheard of though.



Charles.C

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Posted 26 April 2019 - 02:54 PM

Certainly not unheard of though.

 

I suspect only the USA would want to know.


Kind Regards,

 

Charles.C


Scampi

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Posted 26 April 2019 - 03:33 PM

Remember, no single container will be perfectly homogenized for bacteria so it is reasonable that you may get 2 different hits within the same lot


Please stop referring to me as Sir/sirs


Hank Major

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Posted 26 April 2019 - 07:29 PM

I would say that this is like a person with a weakened immune system. If there is a real problem with the system, more than one bacterial infection is not only possible, it is likely.



Foodyy

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Posted 06 May 2019 - 02:24 AM

okay , thank you guys .

But how is that possible ?

Example: we are running whipping cream, one of the tub time : 13:00 tested positive for listeria seeligeri , and another tub with the cream collected from the line 13:03 has listeria Mono .

How possible is that . The samples have been tested for 125 g .


Hi Minia

From my past experience in the microb lab what you are getting is quite possible.

Two ways you can interpret the results.

Firstly, bacteria cells are unevenly distributed. Two species both exist in your product. The first sample u took only picked up L Seeligeri but not L.mono. The second sample vice versa.

Second scenario is, both samples had two species in it. Tests only picked up one which is completely normal for Listeria. It is what they called a “masking effect” of one specie over the other. Causing test result only able to detect one other than two. It is a common limitation on bacteria culturing.

Hope this clarifies your concern.


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