Do you know what’s growing in your dishwasher? Do you want to?

By Seriously Science | January 24, 2018 6:00 am
Image: Flicker/Neticola Sny

Image: Flicker/Neticola Sny

I’ll go ahead and answer that for you — it’s a definite “no.” At least according to this study, which looked at what grows in the biofilms (“goop”) that form along dishwasher door seals. First of all, it’s kind of amazing that anything can survive the crazy environmental fluctuations of a dishwasher: from heat to salts and detergents, dishwashers are designed to destroy organic matter. But life finds a way, and apparently in biofilms, which in this case included large numbers of bacterial and fungal species, many of which can be pathogens. Yum!

Microbiomes in Dishwashers: Analysis of the microbial diversity and putative opportunistic pathogens in dishwasher biofilm communities.

“Extreme habitats are not only limited to natural environments, but also apply to man-made systems, for instance household appliances such as dishwashers. Limiting factors, such as high temperatures, high and low pH, high NaCl concentrations, presence of detergents and shear force from water during washing cycles define the microbial survival in this extreme system. Fungal and bacterial diversity in biofilms isolated from rubber seals of 24 different household dishwashers were investigated using next generation sequencing. Bacterial genera such as Pseudomonas, Escherichia and Acinetobacter, known to include opportunistic pathogens, were represented in most samples. The most frequently encountered fungal genera in these samples belonged to Candida, Cryptococcus and Rhodotorula, also known to include opportunistic pathogenic representatives. This study showed how specific conditions of the dishwashers impact the abundance of microbial groups, and investigated on the inter- and intra-kingdom interactions that shape these biofilms. The age, the usage frequency and hardness of incoming tap water of dishwashers had significant impact on bacterial and fungal composition. Representatives of Candida spp. were found at highest prevalence (100%) in all dishwashers and are assumingly one of the first colonizers in recent dishwashers. Pairwise correlations in tested microbiome showed that certain bacterial groups co-occur and so did the fungal groups. In mixed bacterial-fungal biofilms, early adhesion, contact and interactions were vital in the process of biofilm formation, where mixed complexes of the two, bacteria and fungi, could provide a preliminary biogenic structure for the establishment of these biofilms.IMPORTANCE Worldwide demand for household appliances, such as dishwashers and washing machines, is increasing, as well as the number of immune-compromised individuals. The harsh conditions in household dishwashers should prevent growth of most microorganisms. However, our research shows that persisting poly-extremotolerant groups of microorganisms in household appliances are well established under these unfavourable conditions, supported by the biofilm mode of growth. The significance of our research is in identifying the microbial composition of biofilms formed on dishwasher rubber seals, how diverse abiotic conditions affects microbiota and which key members were represented in early colonisation and contamination of dishwashers, as these appliances can present a source of domestic cross-contamination leading to broader medical impacts.”

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  • Uncle Al

    biofilms (‘goop’) ” Tch, tch – glycocalyx, pericellular matrix, Now you can sell bio-live cultures to repopulate dishwasher microecology so all the little children don’t horribly die of rotted insides.

    Rubber is the problem re ecological low-water washing machine gaskets that ferociously stink. A sophisticated polymer has isocyanuric acid residues whose microbiocidal activity is recharged with halogen bleach-containing detergents re CAS [87-90-1], Symclosene. Surface grafting would likely do it, leaving bulk engineering specs unaltered.

  • Joseph Hertzlinger

    Is biodiversity a Good Thing this week?

  • Namklak

    And I treat it how?

    • OWilson

      (A simple wipe with a bleach soaked cloth can extend your life! :) )

      • Not_that_anyone_cares, but…

        Trigger warning, attempt at cheap humor: Googles first hit on the hazards of bleach: “Exposure to bleach can irritate the nose, eyes, skin, and lungs. Serious side effects of using bleach
        can include respiratory problems, skin burns, damage to the nervous
        system, asthma flares, extreme headaches, migraines, and vomiting.

        • OWilson

          “Used wisely” , but you need an entire government agency to stop folks from drinking it! :)

          In the third world it is a big seller!

        • Mr. Janes

          Ha. Got your comeuppance? I guess you will not attempt humor at this site again.

          • OWilson

            You wouldn’t know humour if it hit you in the face!

            That’s why I have to put a ” :) ” just for folks like you! :)

            Mr/Ms. NTAOC is made of hardier stock! :)

      • Namklak

        Might be wrong, but I thought I read to not use bleach on the seal – it can degrade the adhesive used on the seal or something like that…. I use bleach on the black mold on my front load clothes washer…

        • OWilson

          You don’t use it full strength!

          Instructions are on most Clorox Bottles!

  • OWilson

    There are people out there who don’t know what that black stuff that accumilates on the door seals of dishwashers, fridges and washing machines?

    Do not, repeat NOT, marry these Kardashian Iphone people. They will put your health at risk

    Do not let them cook for you, that is if they actually remember how grandma used to make food at home!

    (A simple wipe with a bleach soaked cloth can extend your life! :) )

    • CB

      Seriously, just wipe it off.

      It’s not that hard.

      I did it yesterday.


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