PEOPLE ARE familiar with the idea of probiotic bacteria, which, if consumed as part of someone’s diet, are supposed to enhance the health of the gut. The gut is home to zillions of microbes of many varieties, and if this microbial ecosystem gets out of balance illness can, indeed, result. Whether consuming probiotic-rich foods such as yoghurts really does promote health is a contested area of science. But the idea that they might do so is plausible.
One commonly promoted probiotic is Lacticaseibacillus casei (known as Lactobacillus casei until April 15th, when its name was changed by the International Committee on Systematics of Prokaryotes in response to a report which suggested that the genus Lactobacillus should be broken up). Now, evidence of the pathogen-fighting abilities of this bug comes from another direction—a study of the nose by Sarah Lebeer of the University of Antwerp.
Dr Lebeer and her colleagues took samples from 100 healthy people and 225 who were suffering from chronic sinus infections. These revealed an intriguing difference between the groups’ bacterial floras. Nearly 80% of the upper-respiratory-tract bacteria collected from healthy people were members of the genus Lacticaseibacillus. In those who suffered chronic infections the proportion was 55%.
That suggested members of Lacticaseibacillus might, indeed, have some protective effect. But correlation is not causation so, to investigate further, the team carried out some experiments using tissue cultures. They pitted various types of Lacticaseibacilli that they had found in their samples against common bacterial pathogens such as Staphylococcus aureus and Haemophilus influenzae.
As they describe in a paper published in Cell Reports, they discovered that the bug best able to stand its ground against these threats was a strain of L. casei called AMBR2. In particular, it was able to cling on to surfaces it had colonised using anchor-like structures that are known as fimbriae and which protrude from its cell walls. It also seemed to have a secret weapon, because it inhibited, presumably by chemical means, the growth and multiplication of its opponents as they came near. It was thus able to defend its turf more effectively than other Lacticaseibacilli.
In light of all this Dr Lebeer wonders if L. casei AMBR2 might be used as a treatment for chronic sinus conditions. As a first step towards testing this idea, she and her colleagues conducted a small trial to see if it was safe. They arranged for 20 healthy volunteers to spray a powder made of dried L. casei AMBR2 into their noses twice a day for two weeks, to check for adverse effects. They noted none. They also looked at whether the strain was able to colonise the nose when so administered, and found that the number of AMBR2 in the nasopharyngeal mix had indeed increased after the treatment was complete. Based on all this, Dr Lebeer suggests that developing a nasal probiotic therapy from this bacterium has the potential to help people with chronic sinus infections, and is something that ought to be explored.■
This article appeared in the Science & technology section of the print edition under the headline “No entry!”