Projects / Programmes
Prevention of growth of pathogenic fungi in dishwashers
| Code |
Science |
Field |
Subfield |
| 4.06.04 |
Biotechnical sciences |
Biotechnology |
Microbe biotechnology |
| Code |
Science |
Field |
| B230 |
Biomedical sciences |
Microbiology, bacteriology, virology, mycology |
| Code |
Science |
Field |
| 2.09 |
Engineering and Technology |
Industrial biotechnology |
dishwasher, opportunistically pathogenic and pathogenic fungi, thermotolerant microorganisms, hygiene, sanitizing procedures
Researchers (13)
Organisations (3)
Abstract
Human households represent suitable habitats for ubiquitous saprobic microorganisms, as well as for extremotolerant ones. A vast amount of literature is available on the airborne fungi, mostly saprobic species, usually classified as a common flora, which inhabit walls and other surfaces in our homes. However, other very special human-made ecological niches inside household appliances, such as washing machines and dishwashers, are also suitable for microbial colonization and can be classified as extreme based on predominant abiotic factors. Our previous research of surfaces within dishwashers, which received enormous public attention because of the alarming results, demonstrated that dishwashers were inhabited by extremotolerant fungi, which otherwise only thrive in special niches in nature. The sampling of 189 dishwashers from different households in Slovenia and around the globe revealed that more than half of the dishwashers contained a consistent fungal community, primarily composed of different thermotolerant yeast species. Noteworthy is the fact that almost all of the identified fungal isolates belong to the species reported to cause systemic diseases in immunocompromised patients and are known as causative agents of nosocomial infections. The predominant species were from a black yeast genus Exophiala, which comprises several species that are important human pathogens. The black yeast genus Exophiala is particularly dangerous as these species are thermotolerant and can thus cause systemic and brain infections even in healthy, immunocompetent individuals. Fungi of the genus Exophiala additionally exhibit tolerance to, high-pH values, high NaCl concentration, detergents and are thus capable of surviving dishwashing cycles. Since it is known from our recent publication that fungi are common inhabitants of dishwashers, the presented project aims to estimate the site and way of their entry into the dishwashers, and their occurrence and extent on different materials inside the dishwashers. The proposed project aims to study mainly black yeasts from the genus Exophiala, the sturdiest fungi determined as common inhabitants of dishwashers. Furthermore, their in vitro physiological characteristics, their response to polyextreme environment on the level of morphology and their ability of biofilm formation will be determined and their transmission from the dishwashers to the environment will be investigated. We expect to identify the physiological growth-limiting parameters of the predominant fungal species. Since the identified species are able to grow at 37 °C they might represent human pathogenic and opportunistically pathogenic fungal species. Thus an almost daily exposure of people to aerosols and/or possibly contaminated kitchenware from the dishwashers might represent an important risk factor for the immunocompromised people, small children and the elderly, as well as for healthy individuals. Based on the results of the proposed project and in close collaboration with the industrial partner, we intend to determine the conditions and to find new technological solutions, which will prevent colonization and growth of the most resistant, pathogenic fungi in the dishwashers and prevent human infections.
Significance for science
The most important scientific findings stemming out of the project are the following: 1.Selected species of opportunistic pathogenic fungi colonize besides dishwashers also washing machines, in particular parts in direct contact with the users, such as rubber seal on doors, drawer for detergent and softener. Usage of softener and high water hardness are the dominant two factors most influencing fungal settlement. 2.Fungi enter the dishwasher (and washing machine) primarily via tap water. All the fungi that represent the core dishwasher mycobiota were detected in the water. Conditions in the appliance prevent the colonization of sensitive species, but enable enrichment of 6-7 selected polyextremotolerant species. Amongst them black yeast Exophiala dermatitidis prevails. 3. Fungi in the dishwasher do not colonize only rubber seals but all sampled sites (10 in total). They spread into the environment via waste water and via aerosols, released at the opening of the appliance. Working surfaces and sinks in kitchens with dishwashers are dominated by black yeasts, in particular Exophiala phaeomuriformis, while white yeasts, in particular Candida parapsilosis, prevail in kitchens without dishwashers. 4.Dishwashers are colonized by mixed bacterial fungal biofilms. Bacteria enter dishwashers primarily via food remains and vessels and not via tap water like fungi. Amongst bacteria that colonize dishwashers are also Escherichia coli and Pseudomonas aeruginosa. Their main virulence factors were associated with adhesion and biofilm-forming ability. 5.Metagenomic analysis of the bacteria and fungi colonizing rubber seals of four selected dishwashers confirmed the results of classical cultivation and exposed temporal synergistic interactions amongst certain species of bacteria that appeared in succession or they mutually excluded each other.
Significance for the country
Project research group has published in 2011 for the first time the discovery that the extreme environment of domestic dishwashers is colonized by selected human opportunistic fungi representing a threat to immunocompromised people. The article has provoqued intense reactions and interest around the world. According to Elsevier these news reached 800 million people. It did not stir only the attention of the lay public but also of the scientific community. It opened a new, almost completely overlooked field of microbiology – extremophilic microorganisms in the extreme environments of our households. The research of extremophiles was limited until then to natural environments. Slovenian research group thus opened a new field of investigation that bridges basic and applied science. Knowledge, experiences and methodologies aquired and developed within the project represent the basis for the development of safe household appliances and for influencing the European standards on this particular field. These have been so far limited to bacterial contaminations, while fungal contaminations remained completely overlooked. By introducing microbiological testing that includes also fungi, the Slovenian industrial partner can establish a competitive advantage on the field of deveopmental strategy of modern, low energy consumption, "smart" and at the same time safe household appliances. Project results enable the formation of technical recommendations and suggestions for actions in the case of testing of new antimicrobial materials and physico-chemical procedures. Further research can be conducted on defined microbial communities which reflect much more accurately the real situation in the appliances then testing on individual planktonic species, as defined in reference standards. Besides, the industrial partner can indirectly confirm the committment of Slovenia to ensure consumer safety, high technological standards and enforce its position and influence in international technical boards. Research results enable cooperation with the relevant Slovenian governmental and international bodies responsible for the introduction of appropriate/new standards on the field. The aquired knowledge stemming from Slovenian research will be further disseminated via lectures, publications, courses and popularisation of science. In this way the results of the project will contribute to the establishment of integral safety measures for the diminishment of contaminations of household appliances and tap water on a European scale.
Most important scientific results
Annual report
2013,
2014,
2015,
final report
Most important socioeconomically and culturally relevant results
Annual report
2013,
2014,
2015,
final report
