Babies who are born with a wide variety of bacteria in their nose are more likely to recover quickly from their first cold, research suggests.
It is hoped the findings may help in the fight against the common cold.
The common cold is caused by a virus, but scientists want to understand how such illnesses are affected by natural bacteria in the respiratory tract.
The study may also indicate why infants who suffer from lots of colds are more at risk of developing asthma later on.
"The respiratory tract is home to a wide variety of bacteria and we are beginning to understand that the types and numbers of these bacteria – what we refer to as the microbiota – can influence our respiratory health," said Dr Roland P Neumann from University Children's Hospital, Basel.
Researchers based their results on swabs taken from 167 babies.
The swabs were taken as soon as the infants developed the first signs of a cold – and then again three weeks later.
Scientists analysed the swabs by testing for the presence of respiratory viruses, such as the common cold, and for the types and numbers of different bacteria present.
Researchers also considered other factors which can affect respiratory health, including the time of year and the baby's age at the point of their first cold, whether the infant had siblings or attended nursery, and whether they were regularly exposed to cigarette smoke.
The study, published in ERJ Open Research, suggests that babies who have a wide variety of different bacteria living in their nose tend to recover more quickly from their first respiratory virus.
By comparison, those who have less variety and more bacteria from either the Moraxellaceae or Streptococcaceae family recover more slowly.
Previous studies have shown a similar link between bacteria found in these family groups and the development of respiratory disease in adulthood.
Researchers have suggested two possible explanations for the link between nose-dwelling bacteria and respiratory infection:
- The presence of certain bacteria causes inflammation and worsens symptoms
- A more diverse set of bacteria offers some protective effect against respiratory infection
The research was part of a larger study that is following a group of babies from birth to investigate the complex interactions of genetic and environmental factors and their influence on lung health.
In the longer term, it could help determine "what healthy microbiota is – and if there is an opportunity to influence it", with probiotics for example, although Dr Neumann stressed such a conclusion was purely speculative at this stage.
Prof Tobias Welte, President of the European Respiratory Society, who was not involved in the study, welcomed further research.
"There is an association between respiratory symptoms in babies in the first year of life and the development of asthma by school age.
"We do not yet fully understand this link but the bacteria living in the upper airways could play a role.
"We need to do more research to understand the relationship between these bacteria, respiratory infections and long-term lung health."