Monday 26 December 2022

Big diversity of fungi residing in hand-washing sink drains

                        Image by Lars Klintwall Malmqvist - Own work, Public Domain,

Sinks and P-traps contain fungi. This is established, but the high numbers and diversity of fungal organisms is an under-researched area.


Research from the University of Reading examined 250 restroom sinks for fungi, recovering black moulds, and relatives of baker's yeast. Each of the sinks had a very similar community of yeasts and moulds, showing that sinks in use in public environments share a role as reservoirs of fungal organisms.


For most people, this isn't a problem, but for those who are immunocompromised, certain fungal species can cause serious infections and it may be prudent for some people to avoid infections by some of the opportunistic pathogens that may be lurking in sinks, such as species of Fusarium.



Some species may cause a range of opportunistic infections in humans. In people with normal immune systems, fusarial infections may occur in the nails (onychomycosis) and in the cornea (keratomycosis or mycotic keratitis).


In humans whose immune systems are weakened in a particular way, (neutropenia, due to a very low neutrophils count), aggressive fusarial infections penetrating the entire body and bloodstream (disseminated infections) may be caused by members of the Fusarium solani complex, Fusarium oxysporum, Fusarium verticillioides, and Fusarium proliferatum.


The types of fungi that live in sinks can tolerate high temperatures, low pH (acidic), and low nutrients. Some will even use detergents, found in soap, as a source of carbon-rich food. Overall, they thrive in the warm and wet environments.


There was no significant observed between male and female restrooms. The 250 sinks tested, all had a very similar population of fungi present.


The implications from the research are that better cleaning protocols need to be developed to address the colonisation of sinks and P-traps, particularly in environments where many people will use a single sink.


A p-trap is a u-shaped bend in the waste pipe that connects a sink’s drain to a home septic tank or to a municipal sewer system. Under normal circumstances, p-traps always contain some water, hence this region of the sink is a major reservoir of microbial contamination.


See: “Mycobial community assemblages in sink drains across a university campus”, published in the journal  Environmental DNA.


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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