Bacterial protection against flu

A recent study by researchers at the University of Michigan in the United States raises the possibility of using microbiome in our respiratory system to defeat the influenza virus.

Usually when people use the term microbiome it is to refer to the bacteria that inhabit our gut. But bacteria are found all over the body, both inside and outside, and the term ‘microbiome’ refers to all of this abundance of bacteria.

Scientists studying the potential of manipulating these bacteria to combat or reduce the risk of diseases, believe that rather than seeing bacteria as an enemy, we could use them to help fight against illnesses. In particular, the researchers were interested in learning more about the role that the microbiome in the respiratory tract play in our susceptibility to the flu (influenza) virus.

Combating the flu virus is important, especially for the very young, pregnant women or the very old in whom the virus could cause serious complications, such as pneumonia.

Although vaccines currently available against influenza are effective, they are not universal in impact against all strains, and not everyone has easy access to these vaccines. Finding a cost-effective and simple way to reduce flu affliction is an urgent public health concern, as according to the World Health Organization (WHO), each year, worldwide more than 650,000 people die as a result of influenza.

Influenza viruses mainly target the epithelial cells of the upper and lower respiratory tract that are lined by swarms of bacteria communities. Researchers wanted to find out whether these colonies impact the ability of influenza virus cause illness.

Previous studies had shown that manipulating the microbiome can change susceptibility to disease. For instance, one study found that treating mice with oral antibiotics led to increased degeneration of the bronchiole epithelium and a higher risk of death after infection with influenza.

Also, earlier research had shown people suffering from influenza had heightened levels of bacteria, most notably Streptococcus pneumoniae and Staphylococcus aureus in their nose and throat. These studies led researchers to infer that there was a clear relationship between the respiratory microbiome and influenza viral infection.

However, so far, an association between the nose/throat microbiome and influenza risk has not been demonstrated in human populations. To investigate this relationship, scientists used data from the Household Transmission Study done in Nicaragua between 2012 and 2014.

The participants were individuals with confirmed influenza. The team followed each of them for 13 days or until they developed flu, whichever came first. The current study took data from the 537 individuals who tested negative for influenza at the beginning of the study.

The researchers took samples of throat and nose bacteria at the beginning of the program. Using DNA sequencing, they were able to differentiate the types of bacteria present into five clusters, and then controlled for other variables, such as smoking, age, cramped living conditions, and flu vaccination.

The team looked at who had which cluster and whether it made a difference on whether they got influenza. And, they found it did. The study participants were found to have a higher or lower risk of getting flue depending on the bacteria community they had.

These results might help explain why some people are more susceptible to influenza than others. The study is also a first step in determining whether probiotics could be developed to combat influenza in future.