Study dives into babies diapers to check out viruses and bacteria

Laval University researchers delved into the contents of babies diapers to look at the bacteria and viruses found within. FILE PHOTO - (AP Photo/Jacquelyn Martin)

A study involving researchers from Laval University found that the gut microbiota of babies contains 10 times more viruses than it does bacteria, and the vast majority of these viruses are unknown to scientists.

The international research team spent five years examining the diaper contents of 647 one-year-old Danish babies. They found 10,000 species of viruses in their feces from 248 viral families, only 16 of which were previously known.

Ninety per cent of the viruses identified are what the researchers call "bacteriophages," viruses that infiltrate not human cells, but rather bacteria to which they pass their genetic code.

This could, for example, make these bacteria more efficient by allowing them to absorb certain nutrients. It could also play a role in the balance of intestinal flora.

"We know that there are bacteria in our microbiota, we know that there are phages, so we wanted to study the interaction of phages with these bacteria, and then see if they have important roles in this ecosystem," said Laval University professor Sylvain Moineau.

The remaining 10 per cent of viruses attack human cells, apparently without making children sick. Their exact role remains to be determined, but they may serve to train the immune system to recognize infections. It is also possible that they are linked to health problems without being known.

There is probably a balance between the bacteria in the gut microbiota, viruses and the immune system, the researchers said.

The bacteria that make up the gut microbiota are much better known than viruses, Moineau said, possibly because they are easier to identify, and therefore to study. Bacteria, he pointed out, have "universal markers" that facilitate their detection and identification.

"It is more difficult to isolate or characterize or identify viruses in our gut soup because there are not these universal markers that are present in bacteria," said Moineau.

The first step to better understand the role of viruses was, therefore, to characterise them, and powerful bioinformatics tools had to be developed specifically for this purpose.

The researchers were amazed at the diversity of the virome (the set of viruses found in the same environment) at the age of one year since babies' guts are sterile at the time of birth. Infants are exposed to bacteria and viruses from birth, through their mothers and the environment, and then when they interact with the world, for example by putting dirty fingers in their mouths.

This work was carried out as part of the COPSAC (Copenhagen Prospective Studies on Asthma in Childhood) project. The project leader, professor Dennis Sandris Nielsen from the University of Copenhagen, explained in a press release that the diversity of the virome may be due to the fact that the immune system has not yet learned, at the age of one, to distinguish between what is useful and what is useless.

This diversity, he added, could help protect against chronic diseases such as diabetes and asthma later in life.

"The next step is to make correlations between some of these virus or phage families that have been identified and then the impact on health," said Moineau.

The Danish data that the researchers have is extremely rich. They will therefore be able to look at multiple factors, from children's diet to the presence of siblings to the environment and the onset of chronic diseases. Further work will be published in the coming months.

The findings of this study were published by the medical journal Nature Microbiology.

This report by The Canadian Press was first published in French on April 22, 2023.