Listeria monocytogenes - How Tough are You?
However, in our quest to learn more about the invisible enemy (and to give the food microbiology forum a little jump start) I wanted to stimulate some discussions beginning with our friend Listeria monocytogenes.
With regard to Listeria monocytogenes in particular:
- What does it look like?
- What foods can it be found on and in?
- Where does it come from?
- What illness or physical symptoms can it cause in humans?
- How do we prevent, control and eradicate it?
- Has it ever caused you or someone you know harm?
- What is its toughness rating – please vote!
The most common occuring in food are L.innocua and L.monocytogenes
L.monocytogenes is recognized as a pathogen and has been implicated in a number of outbreaks. The illness caused by L.monocytogenes is often referred to as Listeriosis
There are a number of infection routes.
Zoonotic Infections are local infection of skin lesions and can self resolve. Time of onset is 1-2days.
Neonatal infection occurs when newborn babies are infected by the mother during birth or cross infection from 1 baby to another. this can be severe and can result in meningites and death. Time of onset is 1-2 days.
Infection during pregnancy from consuming contaminated foods can give mild flu like symptoms in the mother but can have serious implications on the foetus, including spontaneous abortion, foetal death, stillbirth or menengitis. Onset time can be 1day to several months.
Meningitis can also affect the immunocompromised or elderly
Food poisioning by Listeria can occur when there are exceptionally high levels of L.monocytogenes in food (107 per ml). This can bring on vomiting and diarrohea <24hours after consumption.
Outbreaks of listeriosis has occured from food stuffs as diverse as coleslaw to smoked mussels. .
Listeria can survive for many weeks at frozen temperatures and can grow slowly at refrigeration temperatures, it is not very heat resistant
Integrity of raw material is paramount, especially if there is to be no heat treatment of the raw material (ie cold smoking raw fish, or unpasteurised cheeses)
Cleaning in factories is also important as listeria can thrive in dirty, broken drains, unclean equipment such as brushes etc and personnel (boots collect moist debris and this can act as harbourages of Listeria species)
I'm no microbiologist, but i must admit usually if you say Listeria some adopt Hysteria!
My rule of thumb is, if i'm not panicing, then theres no need for others to!
Caz x
Regards,
Emmanuel
Has anyone been made ill by Listeria? Or would you actually know which bacteria had made you ill - pehaps not?
Regards,
Simon
As HACCP would say, It must relate to the product and the consumer..
Sometimes heavy, sometimes light. I entered light.
Rgds / Charles.C
Dealing in food service to a vulnerable population, this bug has seen at least two confirmed deaths (and one litigation still in progress) from our supply chain in the last five years. Our controls have improved vastly since then but we are still at the mercy of a three day turnaround on any test swabs we submit to IMVS Labs. Since my time here, we have eliminated Listeria on all our own made goods through extensive cleaning procedures and, sadly, eliminating a lot of high risk foods from our menu (goodbye eggs and smallgoods). The only time we're caught out is when a supplier provides us with infected foods, we sample (as part of our SOP), product goes out whilst awaiting results and when we get results back we find high counts. Sheesh.
Listeria has also seen major smallgoods suppliers (Conroy's and Garibaldi) fall into major financial and civil action hardship after contaminated product from their outlets was consumed.
Also factored in the fact it doesn't spread from person to person.
Regards,
Tony
Processors under spotlight as food ingredient suspected in listeria outbreak
Listeria Outbreak in Australia
Regards
Tony
So Emmanuel, don´t tell your wife anything. Just make sure any cheese she has was made from pasteurized milk. (I´m under the impression that some artisan cheese makers in France are against pasteurizing milk because it changes the flavor of aged cheese.)
As for Listeria in the general population, at least in Central America, I´m pretty sure that amoebas, giardias and Taenia saginata are much more prevalent. Most people here have learned to live with occasional diarreah.
If it´s not very heat resistant
This is a relative term. One of the reasons for it's choice as a reference (by some authorities) for various foods is due to it's (relative) difficulty for destruction. This aspect is involved in the safety arguments regarding typical UK vs US hotdogs.
Didn't do an exhaustive look but some (representative ?) relative data here -
heat_resistance_data.jpg 32.35KB 76 downloads
(Food Microbiology, Adams)
(D is time in mins for 90% bacterial population reduction at the specified temp./matrix etc, z is the temp. change in degC required to cause a 10 fold (!!) change in D.)
Using comparable temperatures for a given matrix is crucial.
BTW, For cheese, this link might be of interest -
http://www.ontarioch...se_safety_2.php
Rgds / Charles.C
This is a relative term. One of the reasons for it's choice as a reference (by some authorities) for various foods is due to it's (relative) difficulty for destruction. This aspect is involved in the safety arguments regarding typical UK vs US hotdogs.
I agree with you Charles it is a relative term
Heat Resistance of Listeria monocytogenes in Dairy Products
The D-values obtained for both strains resuspended in all the dairy products would result in efficient elimination of the pathogen at 72·7 °C for 15 s
Output from simulations confirmed that pasteurization at the IDF standard conditions of 72°C for 15 sec can ensure at least an 11-log reduction of L. monocytogenes.
Most of the plants I know hold for 25 seconds due to the possible survival of Mycobacterium avium subsp. paratuberculosis on a 15 second hold.
Regards,
Tony
Regards,
Simon
Thanks for the milk links. I noticed that (if I read correctly) the D values in these articles are approx 10x in disagreement with the value given in the link for milk / cheese in my post [the comment in its main text specifically illustrates this also]. I’m sure yr data is correct, just curious where the discrepancy (blunder?) originated.
Also interesting that the heat requirements for milk are seemingly fortuitously lower than officially prescribed for the “typical” food product (min 2mins / 70degC which is predicated for a 6D reduction in L.mono....) According to the standard table in an earlier post here, the 6D also corresponds to 1min@72degC which if my arithmetic has not let me down indicates a D value of 10sec. Maybe a substantial safety factor has been added (
Rgds / Charles.C
Listeria problem is most found on wet floors and condensate from evaporator fans.Also vegetables mostly leeks are mostly contaminated.
Regards,
Jeremy,
Kenya
Listeria problem is most found ............... condensate from evaporator fans
Regards,
Jeremy,
Kenya
Good point Jeremy
Regards,
Tony
As written above it's very easy to find it the food industry (overall raw materials) despite all the improvements done for the process, and so difficult to eradicate it once established.
(right MRios my wife can't eat any unpasteurized cheese with a red wine glass anymore, such a pity...but she has already asked me to prepare some of these special dishes when she will leave the maternity hospital
Regards,
Emmanuel
Not a lot of bacteria remaining as mandatory in the 'new' european legislation (2073/2005), but the listeria still present - like salmonella.
EU Legislation 2073/2005 Microbiological Criteria for Food
Not a great fan of this document:
Regards,
Tony
I have split into own topic for you Tony:
Off topic I know but I would like someone to explain to me how the maximum level for E.coli in ready to eat fruit and vegetables is 1000/g ?
How is the maximum level for E.coli in ready to eat fruit and vegetables 1000/g?
Listeria risks from high pressure cleaning
Regards
Tony
Dear Tony,
Thanks for the milk links. I noticed that (if I read correctly) the D values in these articles are approx 10x in disagreement with the value given in the link for milk / cheese in my post [the comment in its main text specifically illustrates this also]. I’m sure yr data is correct, just curious where the discrepancy (blunder?) originated.
Also interesting that the heat requirements for milk are seemingly fortuitously lower than officially prescribed for the “typical” food product (min 2mins / 70degC which is predicated for a 6D reduction in L.mono....) According to the standard table in an earlier post here, the 6D also corresponds to 1min@72degC which if my arithmetic has not let me down indicates a D value of 10sec. Maybe a substantial safety factor has been added ().
Rgds / Charles.C
Hi Charles
As Tony rightly says, the Dairy industry uses a heat treatment of 25 seconds although legally pasteurisation temperature is 71.7 degrees C for 15 seconds. Even 15 seconds HTST (High Temp / Short Time) allows a log 5 reduction killing 99.99% of viable micro-organisms.
I have a very good document somewhere regarding HTST, i'll have to dig it out, although i'm sure Tony has it too!
Hi Charles
As Tony rightly says, the Dairy industry uses a heat treatment of 25 seconds although legally pasteurisation temperature is 71.7 degrees C for 15 seconds. Even 15 seconds HTST (High Temp / Short Time) allows a log 5 reduction killing 99.99% of viable micro-organisms.
I have a very good document somewhere regarding HTST, i'll have to dig it out, although i'm sure Tony has it too!
Sorry Caz/Charles don't have anything useful loaded on my laptop and I'm away until December. There are a few bits and pieces on the Dairy UK website.
Regards,
Tony
This popped up today almost on cue!
Processors under spotlight as food ingredient suspected in listeria outbreak
Listeria Outbreak in Australia
Update on this Australian listeria source identified
Regards
Tony
(only slightly OT) - This other link within yr excellent first one (
http://www.ap-foodte...ady-to-eat-food
It does rather look as the whole issue of the risk from L.mono is heating up again, ie official "backs" are being analysed for coverage again.
@ Simon - yes (99.9% anyway) but perhaps no eatable chicken left after the "decent" time. (This is the continuous problem of course)
Rgds / Charles.C