Biofilm : la menace persistante pour la sécurité alimentaire expliquée  

Mikkel Svold (00:08):
Hello and welcome to Behind Clean Lines, a podcast by NGI. When people talk about contamination in food factories, oftentimes they associate it with microbes and microbial growth, but there's actually something that's even worse. That thing is called biofilm, and that is also what we are talking about today. Lucky for me, we have someone really clever on this subject in the studio with us on a video link. Deb Smith, you are the... What did I write down? Global hygiene specialist and microbiologist at Vikan. And Vikan delivers cleaning equipment for the food industry.

Hello, Deb. Are you with me?

Deb Smith(00:46):
Hi. Yes, how are you doing? Yes loud and clear, loud and clear

Mikkel Svold (00:47):
I'm good. I'm good.

Now, like I said, biofilm is actually, it's even worse than just microbes. Why is biofilm so important to know something about?

Deb Smith (01:07):
Well, biofilm is basically where the microbes, the individual microbes have a chance to settle onto a surface, grow into colonies, and then cover themselves with a protective slime. Whereas we can combat individual cells quite easily with the cleaning and disinfection that we normally do in day-to-day food safety practices, when they have this protective film over the top, they actually become a lot more resistant to that type of control that we normally apply.

Mikkel Svold (01:41):
And just to set the scene for the listener, do we have any examples of incidents where biofilm and microbes in biofilm have been the cause of any contamination?

Deb Smith (01:54):
Sadly, yes, and it seems to be a recurring thing. I think the earliest example that I can think of dates back to 2008. When I was actually working at Campden BRI at that time, but there was a huge Listeria outbreak in Canada, and that was associated with cooked sliced meats produced by a company called Maple Leaf Foods. Now, the outbreak was associated with a bacteria called Listeria monocytogenes, which is a really nasty one. It kills more people per infection than any other microorganism, so it's a particular concern in the food industry. It's also very much associated with cooked chilled meats.

(02:42):
What happened with the incident in Canada was that they traced the source of the Listeria back to a biofilm within the meat slicing machines. What was happening was when the meat was being sliced, the biofilm was releasing the Listeria bacteria onto the slicing blades and basically inoculating every slice of sliced meat that came out of that slicer.

Mikkel Svold (03:09):
Oh, no.

Deb Smith (03:10):
Yeah, not good, especially as there were 24 fatalities from that incident and 57 cases of Listeriosis, so it was a pretty major outbreak. Of course, not only in terms of the cost to people's lives, but also the cost to the business in terms of the actual financial costs, but their cost in loss of reputation.

Mikkel Svold (03:37):
That's a terrible case, or it's not a terrible case, but it is a good case, but it's a terrible situation. Wow. All right. Because I was just about to ask, I know that the hygienic standards are different in the US and Canada and compared to Europe where we have the EHEDG standards. Are there also European examples of similar severity?

Deb Smith (04:13):
Yes. Yeah, I can give you an example from Denmark, which would probably be quite relevant.

Mikkel Svold (04:18):
Oh, no.

Deb Smith (04:22):
Especially as I actually have eaten this product for breakfast quite often when I'm over in Denmark. Now, let me think when this was. 2014. This was a case where a cooked meat sausage, I think they call it rullepølse. Apologies for my pronunciation, but yeah.

Mikkel Svold (04:44):
Close enough.

Deb Smith (04:44):
It was enough?

Mikkel Svold (04:44):
Close enough.

Deb Smith (04:44):
Good. Thanks. That was obviously prepared and sliced. And unfortunately, this was served to people in an elder home who obviously are older, and some of them had health conditions and they are a particularly vulnerable group for Listeria. In that case, I think... Let me just... I might have to check my notes here. Let's have a look. 17 deaths were associated with that in 2014, so only 10 years ago. And when they investigated that case, they traced that back to a biofilm in the drain of the area where the cooked meat sausage was stored. Obviously, somehow there'd been aerosols and droplets that come from that drain that carried the Listeria onto the cooked meat, and then was then passed on to the people in the elder home.

Mikkel Svold (05:44):
Now, I think this really sets the scene to me that this is something that food companies and also OEMs producing for the food industry, they really take biofilm seriously. But you mentioned just very shortly what it actually is, but can you kind of steelman that for me just a little bit because what is the difference actually between just microbes and biofilm?

Deb Smith (06:15):
Well, the key difference really is that they've got this protective layer. Let's say the microbes, the free microbes settle onto the surface, they gradually accumulate and they build up this biofilm layer, which is this slime that protects them. We know from studies that that biofilm protective layer can make them much more resistant, as I said, to the cleaning and disinfection chemicals.

(06:43):
There was a study, which is quite a long time ago now, but is still very relevant. Hypochlorous acid, which we also still use as a disinfectant, is very effective against free cells. But in a biofilm, the cells in that biofilm can be up to 3,000 times more resistant to attack by hypochlorous acid than free cells. So, the key thing is that it gives them this ability to protect themselves against a lot of the things that we normally used to deal with them.

Mikkel Svold (07:17):
And how do they form? I'm getting patches of biofilm?

Deb Smith (07:23):
Well, kind of. The individual cells, individual cells are with us all the time. They're floating around in the air. They're shed from our skin. People are a great source of bacteria. So, you have to have people in a food factory, the bacteria they bring in with them go into the air, they settle onto a surface. If you give them time and if you give them moisture and if you give them nutrients, all of which you very often find in a food factory, they will grow into these small colonies and then they'll form what's called a monolayer. And then, if they're given more time and they're not disturbed, which is quite often the case with biofilms, they will start to form many layers.

(08:11):
The more layers they form, the more resistant they get to what we would normally do to get rid of them. And then when they get to a mature stage, they then start to produce this, what we call an extracellular polymetric layer, which is this slime that covers them over. And then, the whole thing repeats as a cycle. So when they get old, the biofilms break down, they release the cells back into the environment again, and the cycle repeats.

Mikkel Svold (08:45):
And when you say if we leave them for some extra time, how long time are we talking? Are we talking weeks? Are we talking longer or shorter?

Deb Smith (08:55):
That really does depend on the makeup of the biofilm, so which microorganisms make up the actual biofilm itself. We now know, again, through some of the more modern techniques that we are using that that can be very different. Different biofilms can be made up of different bacteria, and those different bacteria have different growth rates. They need different environmental temperatures and different food sources to produce. So different bacteria, also the different temperature in the environment that they're in, and the availability of the moisture and the food, all of those will affect the growth rate.

(09:36):
It's quite tricky to say for certain, but we do know that the reason that we clean in a food factory after eight hours or 16 hours when we do a shift change is because that limits the development of the biofilm to the monolayer stage, so before it really gets mature and covered by that biofilm. The ones that we worry about most are the ones that you can't see and that go undetected for sometimes years, and they can then obviously be very mature and they can lead to a persistent problem with contamination in the environment, and you won't know where that's coming from.

Mikkel Svold (10:21):
So, you can easily have a biofilm that is completely see-through or transparent that you can't see with the naked eye or...

Deb Smith (10:30):
Not see-through or transparent, but hidden. It might be inside a piece of pipework or behind a wall cladding. And then from there, it gradually seeps out from there and spreads around the rest of the environment.

Mikkel Svold (10:45):
Yeah, yeah. We talked about this just before turning on the microphones. There's something about when you have the microbes gathered together inside of this biofilm, they can somehow communicate. You also mentioned that they produce this outer layer. This sounds so alien to me. Can you try and elaborate that just a little bit?

Deb Smith (11:10):
Well, the outer layer is definitely one of the protective mechanisms we've known about for a long time. But again, once we've got these molecular techniques and we're looking at the microbes on a molecular level, we realize that they actually do a thing called quorum sensing, which is where they generate a chemical that gradually builds up within the biofilm. And when that chemical reaches a particular level, it switches on different genes in different microbes, and then they can form more defense mechanisms against the things that we normally use to get rid of them.

(11:48):
For instance, they can become more virulent, more defensive against the chemicals that we'd use. They can form stronger matrices. They produce little filaments that tie them together called pili or stick them more firmly onto a surface. Or they can actually develop I think called a flagella, which lets them move so they can actually swim. They can swim away from where they are, and they can spread by swimming as well as dispersal through the air. Yeah, they're very tricky, these biofilms, and very clever.

Mikkel Svold (12:27):
Now that we're all shocked, I'm shocked anyway, how would you mitigate the risk when you're in a food factory cleaning, but you say that they can train themselves to stand up to that cleaning method? What would you do?

Deb Smith (12:47):
Well, there's a number of things, and really you mentioned about the different standards between the US and the Europe, and I think you also mentioned EHEDG at one point. A key factor really for trying to minimize the presence of biofilms is to have equipment and facilities that are hygienically-designed. That means not having equipment or buildings where the bacteria can hide in the first place, so making them easy to clean where there's no nooks and crannies for the bacteria to accumulate or be difficult to remove, smooth surface finishes, that kind of thing. That's one of the key things. That's a good starting point to have the good hygienic design.

(13:42):
Then, there's the cleaning and disinfection. Obviously, you have to have your validated methods. I think also having a good maintenance program in place so that you just don't put it in place for once and then forget it. You have to go back and review it and make sure that things haven't changed. And then also having a really good food safety culture, where people understand what the risk from biofilms is, they're trained in what they have to do to get rid of it, and that they actually do do that and they're rewarded and acknowledged for doing that. So, there's a multi-stage approach to it.

Mikkel Svold (14:22):
I think that's also something that we'll talk about in the next episode where you will join us, also where we take a more practical approach to combating biofilms and what can companies do and what strategies can you enforce. I think that's it for now. Deb Smith, thank you so much for joining us for this episode on biofilm.

Deb Smith (14:48):
You're very welcome.

Mikkel Svold (14:50):
And to the listener out there, if you enjoyed this
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