There’s a deadly fungus among us, in the very appliance used to clean and disinfect dinner plates. And the worst part is – the hardy fungi are near-indestructible. Microbiologist Nina Cimerman tells host Bruce Gellerman about the black yeast that has infested the rubber linings of a majority of the world’s dishwashers.
GELLERMAN: Dishwashers are supposed to wash your dishes but there’s a good chance yours may be dangerous to your health. New research finds that the majority of dishwashers in 101 countries are infected with black yeast and other fungi that can make you sick. Not only that, microbiologist Nina Cimerman of the University of Ljubljana says these microorganisms are nearly indestructible.
CIMERMAN: It all started with my dishwasher at home. Once I looked into it and I saw something really black and slimy there, and I decided to sample it because I am interested in these particular, special microorganisms. I do explore them otherwise in hypersaline environments and in glaciers in the Arctic and this - what I saw in my dishwasher - looked kind of familiar. So I sampled it, I took the sample to the lab, and then we looked and we found out that we have - that I have in my dishwasher this really pathogenic black yeast.
GELLERMAN: You find this kind of fungus in glaciers?
CIMERMAN: Glaciers, yes, as you heard me - in the Arctic, and hypersaline environments. All of them live in extreme conditions. I should say that, out of all extreme conditions, the dishwasher is the most extreme of all. And when we did our study of dishwashers, we found out that in dishwashers we have almost exclusively the most dangerous genotype, genotype A.
GELLERMAN: This fungus - what can it do to us?
CIMERMAN: Well it depends how it enters your body. If it enters via a cut, for example, that you would cut yourself with a broken glass that you would take out from the dishwasher - in that way it would enter your nervous system, and it would spread through the nervous system and would end up in brain, where it makes tumors in the brain. The other way of entering the body is if you eat them, which could happen because they remain on the plates and the cutlery that we wash - the acid in the stomach does not kill them. And the third way of entering the body is via air that we inhale. So they could enter the lungs. But that is particularly problematic for people which have cystic fibrosis. We know that two thirds of Slovenian dishwashers, of the ones we tested through our student population, are infected. And when it comes to the global dishwashers - we have samples from all continents - it's more than half.
GELLERMAN: So there’s a very good chance based upon your research that my dishwasher is deadly - it's trying to kill me.
CIMERMAN: (Laughs.) Yeah, well I’m inclined to say yes to that, yeah. If you’re very healthy, you have a very good chance that nothing will happen. But if you belong to the target group, which is elderly people, immunocompromised people, or small babies, small children, which don’t have a very good immune system, yes, you are quite exposed.
GELLERMAN: So how did these fungi manage to get into my dishwasher?
CIMERMAN: Well you see, we actually discovered with these studies that they enter in the dishwasher by tap water. And with each washing cycle, we turn around about 70 liters of water. So it’s a good enrichment process. So they get there, they have the right temperature, which kills competition, they have the right food, and of course they come in numbers because it’s 70 liters we’re talking about.
GELLERMAN: So if these fungi are so tenacious and can live in such extreme conditions, how do I get rid of them?
CIMERMAN: So that’s a good question, and I wish I would know how to answer. And now of course it would be very good to have some reaction from a producer of these appliances - so far nobody contacted me, I should say - who would try to solve this problem. I guess the way to get rid of them - if we can really get rid of them - is to, for example, have dishwashers where it would have a cycle every so often where you can really heat this dishwasher very thoroughly. You know, temperatures - let’s say, 100 degrees.
GELLERMAN: That’s 100 degrees centigrade!
CIMERMAN: Yes. And also to be able to remove or change the seals because the black rubber seals are good food for them - they really like it.
GELLERMAN: They’re eating the rubber seals in my dishwasher.
CIMERMAN: Yeah, they hide in the rubber seals, they use them as a protectant, they make these little holes, and they colonize these rubber seals - and that’s also how they can get away from this heat shock that we exposed them to.
GELLERMAN: What about some bleach? That’s supposed to kill everything, right?
CIMERMAN: Well we didn’t directly apply any bleach on the fungi or on these rubber seals. But you know, bleach and food - that is not such a good combination.
GELLERMAN: So, are you still using your dishwasher?
CIMERMAN: Well I kind of…I’m using more of my hands lately, I have to say. But occasionally when I’m lazy, I still use it. And so far I’ve survived.
GELLERMAN: Talking to us from Ljubljana, Slovenia is microbiologist Nina Cimerman. Professor, thanks again.
CIMERMAN: Thank you.
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