Harmless bacteria may be helpful against meningococcal outbreaks

Nasal drops of harmless bacteria can inhibit a related bug that sometimes causes meningococcal disease, according to the new findings, published online in Clinical Infectious Diseases. The study - conducted among college students, a group at higher risk for this often serious illness - suggests a new approach that could help suppress outbreaks of the disease, if supported by future research.

Funding for the research came from Michelle and John Bresnahan, with their daughter Charlotte, who have raised over £341,000 to fight back against meningococcal disease through research since it took their son Ryan’s life, aged 16, in March 2010. The family set up their ‘a Life for a Cure’ campaign in association with Meningitis Now.

Meningococcal disease is caused by Neisseria meningitidis, which can infect the lining of the brain and the spinal cord, causing meningitis. Strains of the bacteria can also cause serious bloodstream infections. But N. meningitidis can also live silently in a person’s nose and throat, without illness. These “colonised” carriers can spread the pathogen to others through close contact.

In the study, researchers placed drops containing low doses of Neisseria lactamica, a related but harmless bacterial strain, into the noses of 149 healthy university students. A control group of 161 students received drops of saline instead. Nose swabs were taken at regular intervals over six months and tested for both types of bacteria.

Among students who received the N. lactamica drops and became colonised, the harmless bacteria appeared to prevent N. meningitidis from colonising the students’ throats. The “good” bacteria also displaced the worrisome pathogen in those who were already carrying it when the study began. The effect was seen after just two weeks, when the number of students carrying N. meningitidis in their upper airway dropped by 9.5 per cent among those who were also colonised by N. lactamica using the drops. The effect lasted for at least four months.

“It’s the first time that anyone has taken a bug—a friendly bacterium—and has shown that it changes the way that you can become colonised by the meningitis bacterium, Neisseria meningitidis,” said study author Robert C. Read, MD, of the University of Southampton. He described the study as a “proof of principle” with intriguing implications.

Meningococcal vaccines induce high levels of antibodies in the blood to ward off infection, but current vaccines also limit “carriage” of N. meningitidis in the throat, preventing its spread from one person to another. The drop in carriage seen in this study was faster and more persistent than that seen after vaccination. The harmless bacterial strain was also active against more varieties of N. meningitidis.

The findings suggest that N. lactamica may one day help suppress meningococcal outbreaks as a bacterial medicine. Before then, Dr. Read noted, more research is needed, including to confirm that N. lactamica is entirely harmless in a wide population and that it does not change genetically while living in the airway. Determining how to improve carriages rates of N. lactamica also will be necessary before the approach can advance, Dr. Read said.

The study team featured researchers from the Institute of Life Sciences at the University of Southampton and the NIHR Respiratory Biomedical Research Unit, University Hospital Southampton as well as the Sheffield Teaching Hospitals Foundation Trust, Public Health England and the University of Oxford.