Professor Irene Grant (Educator)
I am a Professor of Microbiology and Food Safety at Queen's University Belfast.
Location Belfast, Northern Ireland
Activity
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Professor Irene Grant (Educator) made a comment
Thanks for your positive comments. Pleased to hear you have enjoyed the Food Safety week.
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Thank you for all your comments and discussion about the relative acceptability of sensitivity and specificity. Generally a compromise needs to be reached as few tests for food are 100 % specific and 100 % sensitive. False negative results are of greater concern, as consumers could be put at risk if a food is contaminated with Salmonella but tests negative.
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Yusuf is correct. Rachel and Amy, the negatives need to be correctly classified as true negative (ie not spiked and a negative test result) and false negative (spiked but tested negative) before doing the calculations.
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Carolyn, you have misclassified the true positives and true negatives. There are 9 true positive results, 1 false negative, and 10 true negatives. Your sensitivity calculation is incorrect.
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Professor Irene Grant (Educator) made a comment
Great to see you all doing your homework and reporting back. Keep it up!
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RASFF is EU system. Thank you for sharing the name of another similar system elsewhere in the world.
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You can no longer assume that Salmonella (or many other of the common foodborne pathogens) is only associated with certain animal-derived foods.
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Salmonellla incidence in eggs in Europe has diminished generally due to vaccination programmes and specific Salmonella control interventions, required under EU legislation. In the UK the Lion Mark on eggs indicates that the hens producing them have been vaccinated.
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The RASFF system is a very useful resource for many reasons, so I am very pleased to see that many of you are recognising this fact.
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All good points being made. Thank you for the discussion points.
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I have never heard of protoctists.
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Thank you for finding and sharing these real examples.
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Professor Irene Grant (Educator) made a comment
Thank you everyone for taking part in the online discussions. Some really great points being made, and good to see you responding to each other's comments. Keep it up, for everyone's benefit.
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That's a good point Odin. Hazards will differ by country. No assumptions should be made and the local decisions should be based on scientific evidence about food in the particular country.
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well done, John, your conclusions are correct.
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Good advice Fiona
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Professor Irene Grant (Educator) replied to [Learner left FutureLearn]
Sensitivity and specificity in relation to a clinical treatment is a different thing - it would be diagnostic sensitivity and diagnostic specificity. What we are talking about this week is detection sensitivity and detection specificity. Not sure what some of your post means - you have confused me, so I am sure you have confused other learners also.
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Lateral flow devices are actually one of the less expensive immunoassays
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Toxins accumulate in the shellfish in the water they are harvested from, so could not increase after that. Point of harvesting or processing is the right place to test for shellfish toxins.
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Not too many of the foodborne pathogenic bacteria are capable of growth at correct fridge temperature (which should be 4oC). Listeria monocytogenes is the only pathogen that can actually grow in food in the fridge, but quite slowly; others may remain viable but not increase in number. Check your home fridge temperature and make sure it is operating...
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Professor Irene Grant (Educator) replied to [Learner left FutureLearn]
The RASFF system covers both food and animal feed - that is what the two Fs stand for. Hazards in animal feed may make their way through the food chain to food products.
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Professor Irene Grant (Educator) replied to [Learner left FutureLearn]
Good work Joanne, clearly the topic is engaging your interest.
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Professor Irene Grant (Educator) replied to [Learner left FutureLearn]
Thanks for sharing this video link Joanne.
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Of course it would, a much more thorough evaluation of the sensitivity, specificity, etc, etc., of a test would be undertaken before it would be launched as a commercial test method.
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Your calculations are not correct - the bottom figure in both calculations should add up to 10, not 11 and 9 as in yours. Look at some of the other posts to see the correct calculations. Sensitivity of IMS-PCR test is 90% and specificity is 100%.
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Not sure where you are getting 14 from in your calculation???
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Graham, every detection method will have a limit of detection, which relates to test sensitivity. The limit of detection would be determined by testing food spiked with a range of target pathogen concentrations in triplicate (or more replicates than 3 to increase confidence in result obtained). The limit of detection of the test would be the lowest target...
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Salmonella, Campylobacter, Listeria, E. coli are all relatively heat sensitive so should be easily killed by thorough cooking - the coolest part of the meat joint or chicken portion or whole bird must reach 70oC for at least 2 min, not just the outside surface. Anyone consuming raw or rare meat takes a risk, particularly with minced or ground beef (eg....
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While the 70% contamination level for Campylobacter in UK chickens is a high figure, it has been this level for a number of years, so there is really no surprise in the figures announced yesterday. The disappointing thing is that despite considerable research no effective control interventions for Campylobacter have yet been identified, unlike for Salmonella...
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Chocolate as source of Salmonella in UK in 2006 - here is the BBC News page about the incident http://news.bbc.co.uk/1/hi/5112470.stm - it was Salmonella Montevideo
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Have you ever heard of the hygiene hypothesis? Some argue that if people are exposed to a wide range of microorganisms when they are young they develop more immunity than those who aren't. High immunity = less likely to succumb to illness. This situation would apply to those who live on farms or those who live in poor environmental conditions. The same...
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That's very true James. Any new test will also need to be compared with whatever current test is considered the 'gold standard' method of detecting the same target.
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Please note the results presented were not actual test results for the shellfish toxin LFD but example results to demonstrate the calculations only.
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Of course. Ideal would be a low-cost test which possesses the required characteristics.
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Border rejection is a type of notification not a type of hazard
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For an antibody-based detection method the basic requirement is antibody (polyclonal or more likely monoclonal) specific for the target of interest (toxin or bacterium or allergen). In rare cases a suitable antibody may be purchased and applied to a new detection platform, but more often an appropriate antibody or antibodies will need to be produced by...
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Please note the results presented were not actual test results for the shellfish toxin LFD but example results to demonstrate the calculations only.
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Mercury isn't a shellfish toxin, it is a heavy metal
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Salmonella in eggs largely arises during egg formation within an infected chicken, not as a result of contamination on outside of shell after laying. Ingress of pathogens from egg shell into egg interior may rarely occur under improper storage conditions.
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Just a point of clarification, the RASFF database is not recording cases of foodborne illness but instances of hazard detection. Foodborne illness may only result if the contaminated food has made its way to market, been purchased and consumed. As not all notifications refer to detections in food already on the market, there is no way you can make links...
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Can you supply a web address for PACA or Africa AIMS please?
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For some RASFF notifications there is extra information available. For example, if you use the Consumer Portal (http://ec.europa.eu/food/safety/rasff/for_consumers/index_en.htm) and click on the UK flag the list of latest notifications relating to UK has a column headed More info in some cases with a link you can click on to get more information. This...
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There is a consumer portal as well as the more general portal. Consumer portal is linked from the RASFF homepage. After that you just have to click on the country flag to get individual country information.
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would you like to explain more fully why you say that Patrick?
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The Salmonella and eggs problem of past years has largely been controlled by vaccination of laying hens against Salmonella Enteritidis in the EU, hence the low number of notifications
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Thank you Chrisine for sharing the link for FDA recalls
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Information came from RASFF website, so it must be right Alex.
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You have hit the nail on the head Carolyn. Not sure how many in industry use it, but it is an immense and real time resource of use to them.
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Yes, it is a great resource for food industry personnel and for consumers.
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The purpose of the lecture is not to scare consumers but to make you more aware that such hazards exist and to take care when preparing food for yourself and others.
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That is true, but once these potential sources were identified e.g. the contribution of specified risk material and BSE and the inclusion of bone meal in feed, measures were put in place to prevent such material entering the food chain, i.e. dyeing of SRM upon removal so that it would not be used again in the production process, and banning of inclusion of...
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Possibly allergens used to be classed with chemicals but more and more they must be considered separately e.g. BRC Global Food Standard issue 6
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You are quite right - it has to be a combined effort.
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You need to remember that contamination can be naturally present eg. pathogenic bacteria in chicken, not always the result of deliberate contamination.
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The first part of HACCP (i.e. the HA) is Hazard Analysis. Food producers must go through a process of reviewing all inputs into their production and assess which hazards (chemical, biological, physical or allergens) may be pertinent to their process. They must then (i.e. the CCP part) identify control points in the production process where appropriate checks...
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It is good practice to rinse fruit and peel vegetables before eating raw to reduce microbial contamination. However, your statement regarding presence of pathogens such as Salmonella on fruit and vegetables is rather general - depends which country you are referring to.
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That all depends on your food hygiene practices during food preparation, doesn't it?
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Professor Irene Grant (Educator) made a comment
We mustn't tar every food service/eating out establishment with the same brush. In the UK such outlets are inspected by Environmental Health Officers and given a Food Hygiene rating, which enables consumers to check standards before eating out or buying from a fast-food outlet. Are there similar rating systems in other countries providing similar information?
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A pretty good test, but not a perfect test (which would be 100% sensitivity and specificity).
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Your nose will not necessarily tell you if the food item is safe to eat or not. Obvious spoilage will generally make us throw food out rather than eat it. However, microorganisms and toxins are invisible to the naked eye and pathogenic bacteria won't generally spoil food so there may be instances when a food could be dangerous to eat but still look and smell...
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Good work Ildefonso, lots of interesting statistics in your post.
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As you can see from the list of foods/food products you posted Salmonella turns up in some strange places, not just in animal-derived foods such as chicken and eggs.
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The link you shared just takes us to the Portal search page, not to results of a search. So please share with us all what was the weird notification you discovered.
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Detection sensitivity and specificity are not expressed as proportions.....complete the calculation and express as a percentage.
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We don't want to get too technical!
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Sewage can be source of E. coli and viral contamination of shellfish because they are filter feeders. However, the shellfish toxins are actually produced by algae (algal blooms) or dinoflagellates and accumulated in shellfish - check out Case Study 1 later in the lecture.
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Some correction needed to your post - E. coli is a pathogenic bacterium, norovirus is a virus and cadmium is a heavy metal, so none of these are shellfish toxins and I'm not quite sure how they made it into your list.
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The RASFF system includes notifications of chemical, microbiological, physical and allergen detection. Boiled sweets that are too hard would be a physical hazard and could crack teeth or break into pieces with sharp edges that may cut inside of mouth.
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there are lots of interesting notifications in the RASFF system!! Let's see who can post the weirdest one...
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You make a good point Anne. Certain pathogenic bacteria are linked with chronic long term health conditions, not just acute illness. The fact that foodborne illness is largely preventable means as much as possible should be done by everyone from farm to fork, including the final consumer cooking food properly and not spreading infection in their kitchen.
