An international study led by Singapore scientists discovers bacteria previously thought harmless can worsen existing lung disease.
A team of international scientists has discovered that Neisseria — a genus of bacteria that lives in the human body – is not as harmless as previously thought. In fact, it can cause infections in patients with bronchiectasis, asthma, and chronic obstructive pulmonary disease (COPD).
In a landmark study, published on September 14, 2022, in Cell Host & Microbe, the team showed conclusive evidence that Neisseria species can cause disease in the lung and are linked to worsening bronchiectasis (a type of lung disease) in patients. The scientists were led by the Nanyang Technological University, Singapore (NTU Singapore).
Bronchiectasis is a long-term condition where the airways of the lungs become abnormally enlarged for unknown reasons in up to 50 percent of Singaporean patients. The disease is up to four times more prevalent among Asians as compared to their Western counterparts and can also occur following recovery from tuberculosis. In Singapore, research at Tan Tock Seng Hospital described 420 incident hospitalized bronchiectasis patients in 2017. The incidence rate is 10.6 per 100,000 and increases strongly with age.
Despite its prevalence among older people, no obvious cause is found in most cases of bronchiectasis and the condition tends to arise spontaneously and without warning.
To unravel the puzzle of why bronchiectasis worsens at a significantly greater rate among older Asian patients, the international team — spanning researchers and hospitals in Singapore, Malaysia, China, Australia, and the UK (see Annex) — led by LKCMedicine Associate Professor Sanjay Chotirmall, Provost’s Chair in Molecular Medicine, matched disease and infection data from 225 patients with bronchiectasis of Asian (Singapore and Malaysia) origin to those from bronchiectasis patients in Europe.
Neisseria: not so harmless after all
While Neisseria species are well known to cause meningitis and gonorrhea, they are not known to infect the lungs. Through detailed identification and meticulous characterization, the research team found that Neisseria dominated the microbiome of Asian patients with worsening bronchiectasis.
Specifically, bronchiectasis patients with predominant amounts of a subgroup of Neisseria called Neisseria subflava (N. subflava), experienced more severe disease and repeated infections (exacerbations) when compared to patients with bronchiectasis without such high amounts of Neisseria.
Upon further investigation using experimental cell and animal models, the research team confirmed that N. subflava causes cell disruption, resulting in inflammation and immune dysfunction in bronchiectasis patients with this bacterium.