Field of Science

Fungal research does not need death threats
As scientists we have to sell our work. We need to make our ideas as compelling and WOW!!! as possible to obtain funding, get published in the S/N/C glamour journals, and justify ourselves to the greater community and our peers. But we should never jump the shark.

A recent paper from Fungal Biology proceeds to do just that (subscription required). The press glommed onto to this paper with such objective titles as "'My Dishwasher Is Trying to Kill Me': New Research Finds Harmful Fungal Pathogens Living in Dishwasher Seals" and let's not overlook "My dishwasher is trying to kill me! Deadly bacteria found in household appliances" (Really!?! bacteria!?! Really!?!) A reality based article can be found at MinnPost, for which I provided some thoughts.

Now maybe this is the fault of the media, but maybe not. Actually it's not. Well it's both. As far as the media simply reporting what they were told, they are not at fault. As far as the media actually doing their damn job and not simply being a mouthpiece, they are at fault.

The actual title of the paper is "Dishwashers – A man-made ecological niche accommodating human opportunistic fungal pathogens." That seems fairly benign, although the authors are already introducing the "OMG! We're all going to die!!!" meme by focusing on human opportunistic fungal pathogens. (As an aside, I've always been torn by the phrase fungal pathogen. Is it a pathogen that's a fungus or a pathogen of fungi?)

Fungi live here
So the researchers swabbed dishwashers from all over the world, including the US, and found fungi. This is not interesting. Microbes are everywhere. I am not exaggerating, they are everywhere. The freaking original buildings in Antarctica are being destroyed by fungi. What is interesting is that they found certain fungi frequently, suggesting the environmental factors associated with the dishwasher is most favorable to these types of fungi.

E. dermatitidis
The most common fungus obtained was Exophiala  dermatitidis followed closely by Exophiala phaeomuriformis. As expected these yeast grow remarkably well at high temperature (>45°C), high pH (>10 and even up to 12.5), and high salt (17%). These are all conditions, and harsh ones by most accounts, found intermittently in your dishwasher. Personally, I do find this interesting, albeit descriptive. If you check out your dishwasher seals (or even your refrigerator seals), you can often find some dark gunk growing there. In the case of the dishwasher, you have an idea of what the main fungus might be. (I wonder what's growing on the frig, its certainly a different environment from the dishwasher.)

OK, so how is this related to human health, remember the article's title? Well, E.  dermatitidis has been associated with disease in humans, although it is extremely rare. The word 'opportunistic' in the article's title means something. In the case of E. dermatitidis it means there is something wrong with your immune system. Several studies demonstrate that E. dermatitidis colonizes the lungs of Cystic Fibrosis (CF) patients. However, finding something there does not mean that something is causing a problem. Indeed, the very first sentence of the most recent paper on E. dermatitidis and CF reads "The black-pigmented fungus Exophiala dermatitidis is considered to be a harmless colonizer of the airways of cystic fibrosis (CF) patients." (emphasis mine) Ooohhh, that's some scary shit.

Hopefully, I've noted how the media went off the rails here. The question now is why? Did they make this hype up? Let's see if the authors of the paper in question have anything to say on the topic. The following quotes are directly from the paper.

"The ability of opportunistic fungi to survive near-boiling temperatures needs special attention." Yeah, yeah, we all think our research needs special attention, but why do these authors think this? Is it because this potentially deadly fungus is coming to get us?

"Roughly one-third of sampled dishwashers was infested mostly with one of the two Exophiala species." Anyone else think the word 'infested' was used primarily to elicit an emotional response?

"The presence of such fungi in dishwashers increases the risk of infection through tableware or otherwise." Well that's pretty damned definitive! Im sure there's a reference with data backing that statement up. What? There's not?!? Well, we all know E. dermatitidis infections have increased markedly since the 1970s when dishwashers became common in US households, wait, we don't know that? How about E. dermatitidis infection rates correlate with number of dshwashers/capita, we don't know that either? Hmm, well are E. dermatitidis infection rates higher in employees how spend their days working with dishwashers than others, we don't know that either? Fine! Let's consider this latter sentence  Fonzi's shark.

You know what jerks my chain the most? This is interesting work. The authors have looked in a previously ignored niche and found some interesting bugs. They provide physiological evidence for why these organisms, and not other organisms, are there. This work provides a way to identify natural niches for E. dermatitidis, look for hot high pH high salt locales. This work also highlights how very little we actually know about the microbial world in which we live. There's no reason to pump up the volume with fear (don't believe there was fear, read the comments following the Daily Mail article).

P. Zalara, M. Novak, G.S. de Hoog, & N. Gunde-Cimerman (2011). Dishwashers – A man-made ecological niche accommodating human opportunistic fungal pathogens Fungal Biology DOI: 10.1016/j.funbio.2011.04.007


Pat said...

I know little of this subject but are these people wrong?

"Clinical manifestations include subcutaneous cystic lesions, endocarditis and brain abscesses. E. dermatitidis is neurotropic and cerebral infections are frequently seen."

Mycology Online

"a rare cause of human infection that, when invasive, is nearly always fatal."

Clin Infect Dis

"an uncommon etiologic agent of fatal infections of the central nervous system in otherwise healthy, mainly adolescent patients in East Asia"

Studies in Mycology

The Lorax said...

Are they wrong?

No and yes. Technically they are correct, E. dermatitidis can cause lethal infections in people. These are rare and associated with immune impairment (superficial infections can occur without immune impairment). But in practice they are wrong. There is no evidence suggesting linking dishwashers with E. dermatitidis infections. The authors' attempt to suggest there is is simply fear mongering.

It's like this. Here's a previously known fact: lions kill humans, albeit death-by-lion is rare. Here's the authors' data: we found lions in zoos across the US. And here's the take home message: Holy shit, you could die-by-lion by visiting zoos, be afraid be very afraid.

Pat said...

"In conclusion, we suggest that infections with black yeasts of
the genus Exophiala are severely underdiagnosed in the United

American Deathwashers from Hell

Although they also write that "The reason why the severe syndromes seem to be relatively rare in the United States is currently not understood."

Pat said...

I am sorry, did I misunderstand the meaning of the phrase "otherwise healthy"? I would assume that they had unimpaired immune systems.

Quite a lot of people have impaired immune systems. It might be helpful to know that they should, perhaps, be careful when cleaning their dishwasher or get someone else to do it and use bleach occasionally.

Is there any research into a possible connection between dishwashers and infections with these fungi? Nobody would have thought of it before, surely? They are so rare that there is little data to work with, I would assume. Absence of evidence is not evidence of absence.

I agree that it is probably a lot of fuss that is of no importance except to a very small group of potentially vulnerable people. There are better things to spend research money on. However, they got infected from somewhere as did those with superficial infections. If those infections could be eliminated by simply changing to a different seal material, would that be a bad thing? If the fungal researchers can get funded by the white goods manufacturers all the better. If we can sneak some blue skies research under the radar by scaring a few Daily Mail readers I am all for it.

The Lorax said...

I appreciate the discussion Pat, although I disagree with most of your points.

First, as far as I know and as you suggest, there have been no direct studies on the risk of dishwashers and E. dermatitidis infections. However, that does not mean relevant information isnt available. For example, are those infected found in areas of the world with prevalent dishwasher use. My sense is no, since the greatest risk is in East Asia not the US. Are people most likely to be infected primarily working with industrial dishwashers? Again, I expect the answer is no or the link would have been made already.

Despite the common sense approach of bleach use, you have just advised people to potentially destroy their dishwashers. Bleach can ruin a dishwasher. One easy way to combat fungal growth is let it dry out between loads by simply leaving the door ajar.

FInally, funding. Yes, if resources were acquired to fund additional research that is great. However, is this the research that should be funded with these magically appearing funds? We waste a ton of resources funding BS: Look at the National Center of Complementary and Alternative Medicine. Look at resources spent determining that XMRV is not causing lots of human disease. Look at the resources (monetary and research time) spent looking at the non-link between vaccines and autism. The point is this research found a fungus somewhere interesting. They in no way have evidence that this is a problem. Even in advanced CF patients which frequently have this fungus growing in their lungs, it is unclear if it is harmful.

I would be remiss if I didn't point out that no new resources would be generated for this research. Resources would be taken from one pot of research dollars and redistributed to this 'research'.

If we look in our sinks, soap scum in showers (this has been done), floors, refrigerators, toilets, beds, etc. we will find a bazillion microbes. A few of these will be associated with human disease. Should we give up our houses and live outside? Because they are out there too.

Torbjörn Larsson said...

"If we look in our sinks, soap scum in showers (this has been done), floors, refrigerators, toilets, beds, etc. we will find a bazillion microbes. A few of these will be associated with human disease. Should we give up our houses and live outside? Because they are out there too."

I think you can take that argument much further. The body that is closest associated with us and harboring many microbes, some of which is associated with human disease, are oor own bodies. Should we eschew human company, bath in bleach and entertain the notion of suicide since it is the best way to ensure absence of infectious disease? =D