I am currently in the middle of secret project, which I hope to announce more about in late August/early September. I’m really excited about it but it’s taking a bunch of my time. I’m hoping that you will be just as excited when I can share more details. The wonderful Dr Claire Walker is helping me deliver my passion project by curating the Girlymicrobiologist blog for a few weeks. This means that I hope you all enjoy getting some great guest blogs from a range of topics. Girlymicrobiologist is a community, and all of the wonderful authors stepping up, sharing their thoughts and projects, to support me in mine means the world. I hope you enjoy this guest blog series. Drop me a line if you too would be interested in joining this community by writing a guest blog.
Dr Walker who is a paid up member of the Dream Team since 2013, token immunologist and occasional defector from the Immunology Mafia. Registered Clinical Scientist in Immunology with a background in genetics (PhD), microbiology and immunology (MSc), biological sciences (mBiolSci), education (PgCert) and indecisiveness (everything else). Now a Senior Lecturer in Immunology at University of Lincoln. She has previously written many great guest blogs for the Girlymicrobiologist, including Microbial Culture: An Immunologist’s Side Project Gone Wild.
This weeks blog post continues this months fungal theme (all things yeast) and is from the absolutely amazing Kate Rennie. Kate is a born microbiologist, even if she was diverted by the world of nursing and has gone on to become a cracking Infection Prevention and Control nurse. Her curiosity and willingness to learn and expand her skill sets, makes it no surprise to me that when she decided to expand her hobbies, she decided to go down a route that touches on all things micro.
Before we get into the sour dough however, let’s start by talking what coeliac disease (the condition that leads to the requirement for gluten free bread) as written for us by Dr Claire Walker, our in-house immunologist:
Coeliac disease is a serious autoimmune condition where eating gluten, a protein in wheat, barley, and rye, triggers the immune system to attack an enzyme in the gut called tissue transglutaminase. This damages the villi, tiny structures in the small intestine that absorb nutrients. The result? Symptoms like bloating, diarrhoea, fatigue, and iron deficiency. But it doesn’t stop at the gut. Some people develop dermatitis herpetiformis, an intensely itchy, blistering skin rash. Others experience neurological symptoms such as brain fog, headaches, and numbness or tingling in the limbs. It’s often misdiagnosed or missed entirely.
Around 1 in 100 people in the UK have coeliac disease, but most remain undiagnosed. Diagnosis usually starts with blood tests (like the tTG-IgA), followed by a small bowel biopsy to confirm intestinal damage. These tests only work if you’re currently eating gluten. So if someone’s already gone gluten-free and are feeling better, they need to reintroduce it for several weeks which can cause symptoms to reappear and puts many people off testing.
There’s no cure and the only treatment is a strict, lifelong gluten-free diet. That means no “cheat days” as even tiny amounts can cause damage. It takes serious commitment: careful label reading, avoiding cross-contamination, and asking awkward questions when eating out. But for most, removing gluten thankfully leads to major improvements in symptoms and overall wellbeing.
Blog by Kate Rennie
What am I growing in my kitchen… a gluten free sourdough journey through the eyes of an IPC nurse
I’m Kate, I’m an infection control nurse at GOSH. I’ve worked in infection control since 2020 (1.5 years in primary care, 9 months in community/mental health and I’ve been at GOSH since April 2022). I was diagnosed with Coeliac disease in 2013 and decided 2025 would be the year of new hobbies and I am bored of gluten free bread that resembles cardboard.
I decided to embark on my sourdough journey (albeit slightly late to the party as I know this was a lockdown thing). I didn’t actually know what I was getting into with making sourdough, I read the first few steps and thought it sounded pretty simple, flour and water in a jar.
My flour and water sat on my kitchen side in a jar for 2 weeks (gross), and I named it Marilyn (Mondough)… I nurtured her and fed her daily, for those who may remember Tamagotchi’s, this is how I can describe it and as a previous Tamagotchi owner, I loved it.
Part of me was obsessed with what have created and look forward to waking up each morning to see how it’s looking (highlight of your late 20s) but the infection control nurse in me is slightly grossed out by it. I’ve read a bit more and learnt a lot, she just needed a little bit of extra love and care (troubleshooting) at a few days old.
HOOCH – I’ve only ever known hooch as this from my late teens/early 20s.
Fast forward to my late 20s, this is a sign that your sourdough starter is hungry, it’s eaten all its nutrients, and you must feed it more frequently. I was reluctant to throw her away and start fresh so I added teff flour in the hope she would perk up and SHE DID.
But she smelt disgusting… A familiar reminder of my 16 year old, pre-nurse self, having my long acrylic nails removed in the salon. ACETONE?? Apparently, it’s a byproduct of fermentation…
So, I wondered if this was actually safe to have something fermenting in my kitchen with absolutely 0 knowledge and thinking I’m probably going to poison myself. After a bit of research, I learnt this is normal and how to fix it, yet again, she’s hungry and I’m a rubbish mother.
Whatever is happening inside that jar is creating its own yeast to make it grow which is quite cool! I’m not sure how many people have actually gone this deep into the thought of a sourdough starter, but my IPC brain is fascinated yet disgusted and I want to know more. Do I want to culture it in the lab? Probably not. Am I going to eat it? Most definitely.
Fast forward 2 weeks… My sourdough journey ended abruptly after my first loaf. I felt disheartened that it didn’t turn out like the GF loaves I’d spent too much time obsessing over on Tik Tok. The perfectionist I am wanted the perfect loaf to happen first time, so I abandoned sourdough and ventured into making non-sourdough gluten free bread. I popped Marilyn in the fridge for when I decided to revisit sourdough making and there she stayed for a good 3 months. Apparently, this puts it to sleep, and you can later revive it… but after pulling it out the fridge and seeing a layer of black liquid on top of the starter, my IPC brain got the better of me and I decided with my limited knowledge of sourdough and fermentation at home, it probably was best that I didn’t consume this and decided to throw it in the bin and I spared a brief thought for what Marilyn was and could have been if I had more patience.
I’d hoped this would be a success story about my gluten free sourdough rather than a failure but basically, sourdough isn’t easy and gluten free sourdough, really isn’t easy. It truly is a science.
Gluten free bread making in general is a delicate science because it lacks the key protein—gluten—that gives traditional bread its structure, elasticity, and chew. In wheat-based breads, gluten forms a stretchy network that traps gas bubbles from yeast, allowing the dough to rise and hold its shape. Without gluten, you have to rely on a blend of alternative flours—like rice, sorghum, or buckwheat—each contributing unique properties such as starch, protein, or flavour. Binding agents like psyllium husk are also essential to mimic gluten’s elasticity. No single gluten-free flour can replicate all the functions of wheat flour, which is why crafting a successful gluten-free loaf requires a carefully balanced mix rather than just throwing in a single substitute flour and hoping for the best.
I have been successful on a few occasions in making non-sourdough gluten free bread which has still been a real insight into science in everyday life.
To all life’s problems there are solutions if only we are curious and passionate enough to see them and change direction in order to maximise our successes. It appears Kates’ experience with sour dough as part of her coeliac journey is no different.
I am currently in the middle of secret project, which I hope to announce more about in late August/early September. I’m really excited about it but it’s taking a bunch of my time. I’m hoping that you will be just as excited when I can share more details. The wonderful Dr Claire Walker is helping me deliver my passion project by curating the Girlymicrobiologist blog for a few weeks. This means that I hope you all enjoy getting some great guest blogs from a range of topics. Girlymicrobiologist is a community, and all of the wonderful authors stepping up, sharing their thoughts and projects, to support me in mine means the world. I hope you enjoy this guest blog series. Drop me a line if you too would be interested in joining this community by writing a guest blog.
Previous mycology posts have covered how fungal mycotoxins can cause us harm, and how the new yeast on the block, C. auris, is causing problems in healthcare, but the next two posts will talk about how beneficial fungi can be in our every day lives.
The blog posts will look at how certain yeasts can be used in something that brings me a lot of joy, bread. Many of you will know I’m dairy free, and although I know I should cut down on carbs, you can take my bread from my cold dead hands. It’s one of the few things I can eat without fear and makes me happy. In celebration of this oft overlooked area of microbiology we shall be talking all things baking over the next two weeks.
The first of these posts is written by Dr Walker who is a paid up member of the Dream Team since 2013, token immunologist and occasional defector from the Immunology Mafia. Registered Clinical Scientist in Immunology with a background in genetics (PhD), microbiology and immunology (MSc), biological sciences (mBiolSci), education (PgCert) and indecisiveness (everything else). Now a Senior Lecturer in Immunology at University of Lincoln. She has previously written many great guest blogs for the Girlymicrobiologist, including Exome Sequencing and the Hunt for New Genetic Diseases.
Before I hand over to Claire though, I thought I would talk a little about baking and fermentation. About 50% of all the PhD students I speak to have dreamt at some point of throwing their research out the window, running away and starting a bakery. This may be because baking has a surprising amount of science within it when compared to some other forms of cooking, hence the need to closely align to a recipe. A lot of this is actually because you are working with yeast, a living organism, hence the fact that we are talking about this on the Girlymicro blog, as micro is just cool in so many ways
Fermentation is an anaerobic (occurs without the presence of oxygen) process where microorganisms, like bacteria and yeast, convert sugars into energy and various byproducts, like acids, gases, or alcohol. In baking, it causes yeast and bacteria to convert sugars into carbon dioxide, among other things. This is what causes the dough to rise, as well as adding flavour, and is therefore essential to all things yummy and bread related. The most commonly used yeast is Saccharomyces cerevisiae, and this is one of the reason baking can behave so variably on times of the day or seasons, as both temperature and pH can impact on how well the fermentation process works. It can also mean, if you are impatient like me, you add water at far too high a temperature and effectively kill off your yeast so it doesn’t work at all. Fermentation, and its use in food production, is one of the many examples of how microbiology and microbes impact our every day lives, and of how much poorer our lives would be without them. So I hope you’ll enjoy the next couple of blogs about how baking has both microbiological and immunological links.
Blog by Dr Claire Walker
As I’ve confessed on this blog before,I am, what I like to call, a ‘failed microbiologist’. Many moons ago I completed a master’s qualification in environmental microbiology and dreamed of a career tracking pathogens through our water systems guaranteeing safe water for all. However, I graduated during a recession and started applying for any job that would have me. As luck would have it, I ended up on the immunology clinical scientist training scheme (the story of that fateful application I will save for a later date), and the rest is history. However, I’ve always loved a bit of microbiology and my fascination with all things fermented has taken me on many adventures. Including baking afternoon tea for a GirlyMicro special event!
My treat for finishing my marking this year was a fermentation course at the Welbeck School of Artisanal food learning all about the transformation of food by microorganisms. The word fermentation comes from the Latin fervere meaning ‘to boil’ after Romans watched the bubbles forming when they fermented grapes into wine. Name a scientist who doesn’t love a bit of Latin? There are several biological processes occurring when we ferment foods like grapes, but essentially it is a process by which large chains of molecules are broken down by enzymes into their smaller, tastier, more nutritious, and more easily digestible parts.
The area of fermentation about which I am really passionate is sourdough. Yes, I lived in East London for many years, and yes, I owned a banneton before it was cool. Sourdough doesn’t just indulge my microbiology side project; it became unexpectedly personal. After picking up a particularly unpleasant microbe while travelling in India, I developed amoebic dysentery, and my gut never fully bounced back. I couldn’t tolerate shop-bought bread or much of anything, really. It wasn’t until I began incorporating fermented foods, especially sourdough, into my diet that I noticed slow but steady improvement. (Though let me be clear: this is my experience, not medical advice – if you’re unwell, definitely speak to your clinician!)
For the uninitiated, a sourdough mother, or starter, is a living culture of wild yeast and lactic acid bacteria that needs regular feeding with flour and water to stay active. As a failed microbiologist, I found something oddly fulfilling about sustaining a microbial ecosystem especially one that produces bread with real health benefits. What’s not to love about a culture that feeds you back?
Of course, I’m a dyed in the wool clinical immunologist so I can’t finish up this post without waxing lyrical about the immunology of sourdough. What makes sourdough really special, from an immunologists perspective, is how it supports our gut, which is home to about 70% of our immune cells. By encouraging a healthy mix of gut bacteria, sourdough helps produce bioactive compounds that keep our immune system balanced, strengthening our defenses without overreacting. This means it can help protect us from infections while calming down low-grade chronic inflammation that might otherwise cause problems. So, sourdough isn’t just tasty, it’s a simple, natural way to support a well-regulated immune response. Of course, sourdough isn’t for everyone, especially not for coeliacs. After all, even the most dedicated immunologist moonlighting as a microbiologist hasn’t yet figured out how to turn gluten into something completely safe. Guess some mysteries are still off the menu!
Last week I was running a course alongside some amazing Healthcare Science, IPC, microbiology and estates colleagues. It always amazes me how we start the week as a room full of strangers and by the last day you watch as they have formed bonds and built relationship, and leave having swapped contact details. When I first started running the course it was suggested that paying for food and refreshments was a waste of resources but I stood firm, as I genuinely believe that there by providing food makes a difference, both in how people learn, but also in facilitating networking and having more time in the room. In light of these continued reflections, it felt like today was the right time to talk to you about cake!
Sometimes we all need a little self care
It’s no secret to those of you who read this blog that I love a cup of tea, I’ve posted about it enough. Sometimes tea alone may not be enough, shocker. Sometimes, we need to do a little something more that is a demonstration that we are being kind and treating ourselves. I’m not advocating daily cake or using cake as a crutch for dealing with lives daily issues. I’m advocating for balance and the occasional indulgence that shows we are putting ourselves as a priority every now and again. It’s horses for courses. Some people would go for a ramble, Sunday lunch, and a pint. I’m a cake, bath, and book kinda girl. Life is hard and sometimes taking a little of what you want is not a bad thing.
If you feed them they will come
The second place I’ve found feeding people really helpful is when I’m expecting people to give of themselves or their time, and acknowledging this by giving something back. If I’m running events, especially public engagement events, and people have turned up to contribute or participate then offering food is one small way of thanking people for that contribution. This is especially true if you are running sessions during times when people would normally be eating, such as lunch or early evening events, as you will also get less fruitful discussions if people are hungry or distracted about if they will have time for food.
Sometimes, we all need a little pick me up
I’ve already said that life can be hard and, for me, cake can also be used to enable me to provide comfort. There’s plenty of data about the link between sugar and serotonin, and the ability of a little something sweet to provide comfort is a chemical fact. This one isn’t about sugar addiction and eating our feelings. It’s about a practical step that can enable an interaction that may help someone.
It can sometimes be challenging to talk about difficult topics whilst staring someone in the face. Bringing something else into the mix that allows someone to talk whilst eating, staring at, or playing with the food on their plate, can be a surprisingly powerful tool to enable an individual to get past that particular barrier to expressing how they feel.
Can make someone feel seen
Cake isn’t just about comfort however, sometimes it’s about celebration or just acknowledgement of a change or achievement. There’s a reason we have cakes at our big life moments after all. Taking the time to arrange/make/buy a cake demonstrates that you are invested in the other person. It demonstrates that you care or are acknowledging something that can be a big deal to the other person. It’s a way of not letting moments past by unmarked. Making people feel seen is one of the best gifts we can give, and providing cake is just one way of doing it.
Breaks down barriers
We all sometimes put our defences up when we are facing the unknown or feel at risk. This can happen in all kinds of situations, from attending an education event where you worry about sticking out to meeting a lot of new people at a friend’s social gathering. Much like the weather, food, and the quality or lack of, can be used to provide an ice breaker that can make many social situations that little bit easier. The whole ‘oh you went for the lemon drizzle’ comment can open that first difficult conversational door.
Is an act of show don’t tell
Too often, it’s easy to make conversational pleasantries, especially in leadership. We all know of scenarios where the words that come out of the mouths of those in charge are not matched by their actions. I think it is therefore important to consciously undertake acts of ‘show don’t tell’ where possible. In these cases, simple gestures, such as a card and cakes for Biomedical Science day, demonstrate that you not only recognise that such a day exists and is important to people, but that you care enough about those people to engage with it, even if you are not a Biomedical Scientist. There are plenty of examples of this, but I think as leaders we should think more about whether words alone are enough.
Takes the financial burden off another
I spent a few months in the states on sabbatical before the pandemic and one of the things that struck me was that whenever I went to an academic meeting at breakfast, lunch or after work, there would always be food provided. It was both nice and plentiful, and at one point I was chatting with some of the students who attended about whether this was standard. They said in most good departments it was because university fees and living costs are so high that many post graduate students can’t afford to buy food despite working extra jobs. Obviously that is an awful state of ‘normal’ but it also struck me that I don’t know that my students would be so open about not being able to afford things. Since then, whenever I take any one of my team, students, or staff out, I will insist on paying just in case and as a demonstration of the fact that I care about them. As I said, life is hard, so let’s try and make it easy.
Supports levelling of hierarchy
A lot of reasons I’ve talked about so far are linked to leadership, but there are other reasons where deliberately using the offering of food to remove hierarchy is important. Conversations and openness can be inhibited by artefacts such as hierarchy. There are reasons why, in high stakes moments, hierarchy in healthcare may be beneficial, but most of the time it can run the risk of inhibiting openness and collaboration. Food can really support breaking down some of these inhibitors. Some of that is because we will often move to a more neutral, less loaded, location in order to have our tea and cake. It’s often not going to happen in a consultants office. The other reason is that food is pretty embedded as a way of demonstrating friendship in most human cultures, and therefore it works on a subliminal part of our minds to support engagement.
Buys time away to focus on each other
Another benefit of the fact that we may need to step into another environment to enjoy our tea and cake, is that you are also removing yourselves from distractions. I don’t know about you, but I feel like I have emails that drop into my inbox and pop up every few minutes. If it’s not emails, it’s calls, or someone knocking at the door. Stepping away from those distractions so you each have the mental space and capacity to undertake some active listening and really be in the moment with each other is pretty priceless, way more than the cost of some tea and cake.
Gives the gift of time
One the things I have least of in my life is time. I have very little capacity to do anything other than survive and work. Therefore, if I take the time to make Christmas puddings for my friends, or bake a cake for colleagues, I think it goes some way to showing what those people mean to me. It means that I prioritised that act over something that I could have chosen for myself, such as bath and book time. I also hope that it holds greater meaning for them because they know how hard it is for me to carve out those moments in my life. I could buy a cake, and I often do, but when I can I will also try to give the gift of time by making one myself.
Enables you to show you care about the person not just the task
I often take my team out for tea, and sometimes lunch, but those sessions are usually working sessions. Sessions where we may be eating but we are also planning a project, talking through results/feedback, or developing a strategy. It’s so important sometimes to do the same thing but without work being on the table. I can be a pretty task focussed individual. It’s one of the reasons I probably ended up as a scientist. For getting stuff done, all that is pretty great, but to really do it well requires us to value the person and not just the task. Every now and again it’s important therefore to step away from the normal and catch up without a job or agenda, and to just be in the company of people you work with. It helps you get to know them better as people. To understand the challenges that they have going on, and not just in their work life. To value them as people, not just as cogs in the machine. It’s easily forgotten but crucial to do.
Can be a great educational tool
The slide below is one that I use to talk about molecular typing through the medium of cake. I find it works because most people know about cake, whereas many people don’t know about molecular typing. I talk about phenotypic, or growth based identification, being like a Victoria Sponge. You can see everything, you don’t need to cut it open to work out what it is. It’s a classic and will please most people most of the time. I then talk about fragment based typing, things like PFGE, VNTR, typing that looks at sections of the genome in order to decide on whether two things are linked or not. For the most part, this is like a meringue dessert. You can tell it from the outside that it’s meringue, but won’t be until you cut into it and get more information whether it is lime or lemon. Finally, you have whole genome sequencing, which is more like a pie. You can look at something and know that is a pie, but when you open it up you can get all kinds of information. You’ll be able to tell whether its fruit or savoury, what kind of fruit, and you’ll even be able to have a guess at what spices were used. It all depends on what level of information you need before choosing your cake.
Sometimes, it’s just nice to eat cake
Finally, and not to be under estimated. Sometimes it’s just nice to have cake. Be it because the world is glorious, or the world is gloomy. Be it on your own in glorious solitude, or to spend time with someone you care about. Be it on your sofa, tucked up in bed, or at the Savoy. One of the best things about the joy of cake is the flexibility to enjoy it (or not) however you wish!
This month is the start of a painful re-entry into normal life. Normal life in terms of work demands, normal life in terms of commuting and normal life in terms of getting back to not eating party food and leftovers for at least 50% of our meals. Now, mummy Girlymicro, Mr Girlymicro, and I have done our fair share of celebrating over the last few weeks, including eating out at large catered events and throwing our own parties for friends. Clinically, norovirus is now giving us its cyclical peak, and there was also a lot of food related outbreak news over the holidays. I thought, therefore, that I would start this years IPC related posts with one on foodborne outbreaks and the kinds of organisms involved.
Food related sickness and outbreaks can be caused by a number of different microorganisms and through a few different routes. The two main routes are infection and intoxication, and these are related to the organisms that tend to be the causative agents. The foods that are linked to these routes are also different, and if investigating can give you an idea of what you might be looking for, especially when combined with presentation, both in terms of clinical symptoms and speed.
Infection vs intoxication
Intoxication based food poisoning is usually linked to rapid onset symptoms following the ingestion of the food i.e. a matter of hours. This is because the symptoms aren’t related to an infection based process, where symptoms are linked to the invasion and replication process of the organism. There are two main types of toxins, heat stable and heat labile toxins. Heat stable toxins can be problematic, as once present in food these cannot be removed purely by re-heating to an appropriate temperature. Heat stable toxins, such as those produced by Bacillus cereus, are produced when the bacteria are present, hitting the right temperatures then kills the bacteria but the toxins remain. This process can be exacerbated when foods are not rapidly chilled or are left at a temperature where the bacteria could grown, there is therefore a prolonged period when toxins could be produced. Toxin related food poisoning (intoxication) can be caused by both bacteria and fungi.
Infection based food poisoning is linked to the ingestion of the organism itself, and presentations are therefore usually delayed as the organism needs to infect the gut mucosa. Many organisms that produce toxins can also cause infection related symptoms if present in high enough loads, and if suitable temperatures for bacterial kill are not met. Infection based food poisoning can be due to viruses, such as norovirus, parasites, such as E. histolytica, as well as bacteria, and the risks are often related to food hygiene efficiency as well as production factors.
Patient management
Most food related illness self resolves and management is mainly focussed on maintaining hydration and electrolyte balance. There is usually a requirement to undertake a minimum isolation period of 48 hours post symptoms in order to prevent any ongoing risk of person to person transmission, even if the original acquisition is thought to be via a food related source. Isolation may need to be prolonged in relation to certain groups because of the risk of ongoing to spread to others, either through personal hygiene awareness or through work based activity.
Recommendations for the Public Health Management of Gastrointestinal Infections 2019: Principles and Practice has a lot more detail on the main organisms associated with foodborne illnesses and some of these requirements for isolation. I’ve attached a copy below, but the link is also here in case it’s useful.
If symptoms continue for period of a week or are especially severe it may be necessary to take samples in order to identify a causative organism in order to support patient management. When taking a patient history it’s important to capture any patient specific risk factors (see below section on risk groups), travel history, recent event attendance history and details of hobbies (such as preserving) that may impact of food ingestion patterns. Additional individual management options can include antimicrobials (antiparasitic or antibacterial) and for non-bloody diarrhoea without fever antidiarrheal agents.
How do these organisms get into food?
Organisms can get into food from numerous sources. They can be present in the environment in which the food comes from, such as manure that is used to fertilise salad plants can contain organisms, like E. coli, even more so if human waste is used. Food, such as oysters, can be contaminated as part of their life cycle as filter feeders if they are growing in an environment where they are exposed to animal or human waste, and so can harbour organisms like norovirus and become highly loaded. Food can also become contaminated as part of the production or manufacturing process, contaminated from other items that are produced in the same facility, contaminated from the processes, such as the water or preservatives utilised, or from failures in the preservation process that would normally have removed organisms that are naturally present linked to food.
Organisms can also come from the humans involved in the process. Those manufacturing or handling the food may be carrying or infected with organisms, whether symptomatic or not. A Staphylococcus aureus colonised person making sandwiches may contaminated the food they are making. An asymptomatic norovirus infected canteen worker could expose those being served food by unwittingly contaminating food and/or serving implements. In the case of bacteria, low level contamination from those producing the food may then be able to grow up to levels where ingestion results in symptoms if the processes are not well enough controlled.
Food processing and manufacturing
Most food preserving techniques aim to ensure that if contamination occurs during production or manufacturing it is not able to replicate to the point where the organism would cause symptoms in those who ingest them. Many preserving techniques aim to control organism survival or replication/loading via either temperature, cell lysis/resource availability or both. There are two main groups of techniques, either physical or chemical.
Some of these processes are more prone to risk of failure than others, both depending on the process and where is it being undertaken. When undertaken in food manufacturing, these techniques are usually undertaken under highly controlled conditions using the HACCP process in order to manage some of this risk variance:
Food preparation in the home
Obviously, none of us are following HACCP processes when we are preparing food at home, that doesn’t mean that there isn’t any risk to home cooking. One of the hazards linked to cooking at home can be the home environment itself. I’m still aware of people who wash out chicken or turkey cavities in their kitchen sink, unaware of the droplets that are produced and how they can then deposit on other surfaces, which are now contaminated whilst appearing visibly clean. Other hazards can link to the fact that most of us don’t have access to rapid (blast) cooling, and therefore when cooking big batches of food and putting in the fridge, the cooling process may not be fast enough to prevent bacterial growth. Also, in terms of equipment, I work in IPC and I’m a bit of a control freak so I possess things like meat thermometers, in order to ensure that meat has reached appropriate safe temperatures. I am aware that not everyone lives in this particular world, and so may not have some of these pieces of kit lying around.
Most of the time if you end up preparing food less well at home the consequences are non-ideal but not massively serious, however, if you have an ‘at risk’ member of your household or visiting then it becomes more important to focus on controlling these risk, both through the food that is brought and how it is prepared.
Food preparation (catering)
We’ve already talked a little about the HACCP processes that are put in place to control risk in formal settings. Catering can be a tricky area of risk, even if undertaken by professionals. It is one thing to undertake catering in your restaurant or a space you work in all the time. Catering however, is often undertaken in sites that are not the ‘home’ of either the professional or the average person. Catering equipment can be hired to serve food in church halls, for weddings or other special events. It can also be undertaken on beaches, in forests and other remote locations with variable levels of power to support refrigeration. This can mean that control processes, such temperature control, are undertaken in atypical ways, such as temperature control using ice packs, which will have variable efficiency depending on external factors, such as ambient temperature.
Home catering for parties also brings risks. I love to throw an afternoon tea party for charity, but that means that I am suddenly trying to put waaaaaay more in the fridge than I normally would. Food may be out on a table for a number of hours. Some of the food may also be high risk, such as cheese or smoked fish, and it will be next to less high risk foods. Also, if you are not used to prepping food for large groups, you may inadvertently increase risks by the order in which food it prepped. That is without the risk of people bringing food to contribute to yours which you don’t know the origins of, or people picking up food with fingers and therefore increasing risk of spread if they have anything onboard.
Food storage
Once all of that catering is done, you are then left with a decision, what do you do with all the food that is left? Do you then try and shove it all in your fridge or freezer? Do you give it people to take home in Tupperware pots? How much have you taken into account the length of time that food has been non-temperature controlled? What does that do to the use by? Is everyone aware of any re-heating requirements or the dangers irrespective of re-heating of intoxication?
Issues with food storage are true not just for party catering, but also for batch cooking, something a lot of us are doing more and more of now the weather is colder and because food it more expensive. Foods like stews and rice dishes, which are high risk for intoxication, are also the kinds of foods that fulfil a lot of batch cooking requirements. It is really important to bear these risks in mind, ensuring rapid cooling and that temperature is monitored appropriately.
This also extends to ensuring that even dry goods are stored appropriately. We’ve all been there when we’ve found the pack of spice that 15 years old. Spices, canned goods and other preserved food have been identified as the source of outbreaks, and even when originally in good condition can become a risk if not well maintained, such as dented cans or if moisture has gotten into packets.
What kind of incidences are we talking about?
Over the Christmas period there have been two well publicised food related outbreaks, one linked to E.coli in cheese and one linked Cronobacter sakazakii (previously Enterobacter sakazakii) in infant formula.
BBC News – One dead after E. coli outbreak linked to cheese
This outbreak was linked to the presence of STEC toxin producing strain of E. coli. This leads to an intoxication that can impact of kidney function. Although not stated, elsewhere it was reported that the cheese may have been made from unpasteurised milk, removing one of the stages used to control organism risk in food production.
Advice for individuals from UKHSA included:
“Washing your hands with soap and warm water and using bleach-based products to clean surfaces will help stop infections from spreading. Don’t prepare food for others if you have symptoms or for 48 hours after symptoms stop.
“Do not return to work or school once term restarts until 48 hours after your symptoms have stopped.”
The other recent recall was linked to possible contamination of infant formula detected at manufacturing. Formula feed outbreaks linked to Cronobacter sakazakii have been noted in the past, with a large outbreak in France being the last large scale event. Infection does not just lead to GI symptoms but is associated in some patients with presentations such as blood stream infection and/or meningitis.
The formula included in this recall is mostly used in healthcare or is prescribed to individuals. This makes it critical as it is likely to have been given to an ‘at risk’ population. Milk related contamination is particularly challenging as heating impacts the nutritional content of the milk and so use of thermal risk reduction is not straight forward. Some hospitals, such as the one where I work, undertake an additional step, pasteurisation, for any formula feeds due to be given to high risk infants because of this well acknowledged risk in order to support infection risk reduction.
BBC News – Baby formula recalled over bacteria contamination fears
Current and Future Perspectives on the Role of Probiotics, Prebiotics, and Synbiotics in Controlling Pathogenic Cronobacter Spp. in Infants October 2021 Frontiers in Microbiology 12
There are obviously multiple examples every year of foodborne risks linked to contamination at source or HACCP failure, but these are the ones that have been most recently featured in the national press.
Are any groups at higher risk?
Although food related infection or intoxication can impact anyone, certain groups are more at risk of significant symptoms requiring treatment or are more at risk linked to certain organisms in terms of presentation. These groups are your very young, very old, the immunosuppressed and pregnant women. The very young and very old are more likely to need support linked to dehydration, and all 4 groups are likely to be less able to mount immune responses to invasive infection. The immunosuppressed and pregnant women have specific guidance linked to avoiding high-risk food groups because of severity of impact if infection occurs.
One particular organism linked with significant infection risk for pregnant women and the immunosuppressed is Listeria monocytogenes.
Microorganisms 2022, 10(8), 1522
Listeria crosses the gut wall at locations known as Peyer’s patches, and from there invades lymph nodes and blood. Once in the bloodstream, it can progress to cause meningitis/encephalitis by infecting the brain. In pregnant women it can also cross over into the placenta, where it can cause infection in the foetus/unborn child. Foodborne listeria outbreaks have been associated with a wide variety of foods, but are often linked to preserved foods and cheese.
There are a number of stages to investigating foodborne outbreaks. Initially, there will need to be some sort of flag to suggest an outbreak event. This is usually a number of people attending GPs or A&E linked to a single event, an uptick in samples positive for a specific organisms that is noted through lab reporting, or any cases of specific reportable organisms which will then get followed up.
Depending on the circumstances, a combination of the following steps will be undertaken:
Patient questionnaire (case)
Questionnaire of those who attended the same event but did not get sick (control)
Sampling and microbiological testing of possible implicated food, if still available
Sampling of the production environment, such as factories or restaurant kitchens
Investigation needs to be undertaken to identify the target food or batch as most production facilities will make more than one kind of food and will have multiple batches. If the outbreak is linked to a specific event, multiple types of party or other food is likely to have been available. Getting more information about what those who got sick ate vs the others enables you to narrow down what the culprit might be.
Once you have your questionnaires, it’s time for a little bit of stats. This enables you to calculate something called the relative risk for the cohort. The cohort being all those people who were at the same event, ate at the same restaurant, brought food from the same factory etc. This will include those who became unwell and those who did not. For each type of food or batch you can calculate a ratio of the risk of disease (infection/intoxication) in people who have been exposed (ate that food) compared to those unexposed (decided that food was not for them).
You then get a list of risks for different food types eaten. So if the following food was available at our event you can then undertake the calculation:
pigs in blankets
mini fish and chips
turkey and stuffing roulade
mini pavlova (with cream)
cheese pinwheels
If the number if >1 then it indicates and increased risk, if RR = 1 then it doesn’t impact on risk, and if RR <1 then there is a risk reduction. So in the case of our party food:
pigs in blankets RR = 1
mini fish and chips = 0.98
turkey and stuffing roulade = 1.73
mini pavlova (with cream) = 1.1
cheese pinwheels = 0.99
In conclusion………the turkey probably did it!
I hope that’s helpful, I know there’s loads more that could be covered, and if you are interested in anything in particular drop me a comment and I’ll see if I can post a follow up. The main take away is that there are multiple organisms that can cause foodborne infection/intoxication, and whether it’s home or out and about we can all be impacted. For most of us, it’s an unpleasant but low consequence event, but there are are people and populations where the outcomes can be much more severe. So, if you’re ever asked to complete a questionnaire please do so, and don’t ignore those news articles that tell you to throw an item away as it’s not a risk worth taking.
Girlymicro 