When it comes to our health, we're quick to paint bacteria as the bad guys, but that's not always the case – we need certain bugs to colonize our bodies to help us perform vital functions like digestion. Now researchers from the University of Michigan have discovered a new symbiotic relationship we have with bacteria in our noses and throats, some of which may help fight off the flu virus.

One of the main functions of the nose is to act as an air filter, catching inhaled pathogens before they can get into the body and cause harm. But of course it doesn't always work, and sometimes the flu virus slips through anyway. The researchers on the new study wanted to investigate if the bacteria that colonized the nose and throat played any part in whether or not someone exposed to the flu virus developed the illness.

To do so, the team analyzed data gathered during a longitudinal survey conducted between 2012 and 2014. The Nicaraguan Household Transmission Study followed 717 participants from 144 households in the Central American country, in order to study how the flu virus spread between family members and communities. Over the years since, the data gathered has been analyzed in a range of different ways for different studies.

In this latest analysis, the University of Michigan (UM) team looked at the 537 participants who didn't have the flu at the beginning of the study. Samples of nose and throat bacteria were taken from each of the participants, and the UM researchers ran DNA sequencing on these to figure out which bacteria were present and in what amounts.

The team identified five different clusters of bacteria species, which they dubbed community state type (CST) 1 through 5. They then plotted out which CSTs people had, alongside whether or not those participants contracted the flu by the end of the study. The idea was to check whether certain clusters of bacteria reduced the likelihood of getting sick.

And sure enough, they did. First the team adjusted for other factors that might influence each person's likeliness of getting the flu, like their age, whether they'd been vaccinated, their exposure to tobacco and how crowded their household was. Those things aside, the researchers noticed that in particular, people with CST 4 – which includes comparatively high levels of bacteria like Fusobacterium 1, Neisseria 1 and Streptococcus 1 – seemed to be less likely to contract the flu than those with other CSTs.

While the link is intriguing and may eventually lead to new treatments for illnesses like the flu and pneumonia, the team says it's still very early days for the research.

"The potential is really great, but there is so much we need to learn before we can successfully manipulate the microbes living in and on our bodies to prevent disease," says Betsy Foxman, lead author of the study. "I love the idea of working with our microbes as opposed to seeing them as an enemy that needs to be eradicated. Working with our microbes can preserve life-saving treatments like antibiotics for when we really need them."

The study was published in the journal PLOS One.