Discovering new methods of inhibiting carriage of N. meningitidis with N. lactamica

Background

The bacterium that causes meningococcal disease, Neisseria meningitidis, is carried in the back of the nose and throat (nasopharynx). In most people this is harmless, but in a minority of individuals carriage of meningococcal bacteria leads to invasion of the bloodstream and life-threatening disease.

In a previous study, the research team found that inoculating adult volunteers with Neisseria lactamica, a harmless ‘cousin’ of Neissseria meningitidis, possibly prevents N. meningitidis carriage.

As a result of this finding, the team proposed that they attempt to answer the following questions:

• Does N. lactamica prevent N. meningitidis from living in the nasopharynx?
  
• Does N. lactamica displace N. meningitidis already living in the nasopharynx?
  
• Are there individuals who are naturally resistant to any Neisseria carriage?
  

What did the researchers do?

310 young adults were recruited to the study. Approximately half were given a dose of N. lactamica into the back of their nose and the other half received control solution. Swabs were taken from all participants at several time points to see what bacteria were being carried and how these changed over time.

The difference this could make

If it could be proved that N. lactamica does prevent carriage of N. meningitidis then this could allow new ways of reducing carriage of meningococcal bacteria.  Inoculation with N. lactamica could be used to rapidly control outbreaks of meningococcal disease.

What were the results of the research?

Professors Read and Gorringe have successfully answered the three questions in the original project proposal. To summarise, they have confirmed that:

• N. lactamica carriage inhibits acquisition and carriage of meningococcal bacteria
  
• Inoculation with N. lactamica can displace existing N. meningitidis carriage
  
• There are not individuals who are naturally resistant to Neisseria carriage
  

Significantly, the inhibition of meningococcal carriage by N. lactamica is even more potent than after meningococcal vaccination. This research is therefore potentially hugely valuable. If researchers can fully understand how and why N. lactamica both inhibits acquisition and displaces carriage of N. meningitidis, it may be possible to use it in a novel bacterial medicine to rapidly control an outbreak of meningococcal disease. It could also become the basis of a future vaccine strategy.

Researchers 

Professor Rob Read and Professor Andrew Gorringe 

Institution

University of Sheffield and HPA Porton Down

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