Groundbreaking study: every home has unique water microbiome

Is the water from your kitchen sink the same as that from your shower or next door? Is it always safe to drink? Apparently not! 

Even water hosts diverse microbial communities. These microbiomes differ significantly and are associated with health risks. But that’s not all: according to a new study ¹ published in Nature, they share antibiotic resistance mechanisms.

Few studies on water quality, straight from the tap

The vast majority of microorganisms present in drinking water usually pose no threat to human health. As an integral part of our exposome, they may even contribute to the balance of our gut microbiota. But drinking water can also contain antimicrobial resistance genes (its “resistome”) and pathogenic microorganisms.

Although the quality of drinking water in distribution networks is closely monitored at municipal level, little is known about the water that arrives at taps inside the home. Certain specific factors (reduced pipe diameter, higher temperatures, nocturnal stagnation, type of water heater, etc.) may influence the bacterial communities present in this water.

To better understand these characteristics, researchers recruited residents from 11 households in St. Louis, Missouri (United States). They were asked to collect water from their kitchen and shower taps for a week so that variations – particularly day-to-day variations – in microbiota and the resistome could be examined.

Major findings to consider

Surprisingly, the results of the analyses indicated that the water in each household has a unique microbial signature differing from other households. Furthermore, the microbiome of kitchen water differs from that of the shower.

The researchers also noted the presence of various pathogenic microorganisms, particularly in shower water. For example, Mycobacterium chelonae, a bacterium responsible for skin infections, was present in 50% of households. 

However, what most caught the researchers’ attention was the presence of antimicrobial resistance genes, whose profile was this time similar from one household to the next. They found 162 of such genes, some of which could confer resistance to aztreonam and meropenem, two major antibiotics used to treat recurring infections.