A seemingly mild bacteria, Neisseria, has been found to be more harmful in the lung than previously thought

A team of international scientists led by the Nanyang Technological University, Singapore (NTU Singapore) has discovered that Neisseria – a genus of bacteria that lives in the human body – is not as harmless as previously thought, and can cause infections in patients with bronchiectasis, asthma, and chronic obstructive pulmonary disease (COPD).

In a landmark study, 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.

Bronchiectasis is a long-term condition where the airways of the lungs become abnormally enlarged for unknown reasons in up to 50% 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. 

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.

Devastating disease

The international team, 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.

Chotirmall said: “Our findings have established, for the first time, that poorer clinical outcomes such as greater disease severity, poorer lung function and high repeated infection rates among bronchiectasis patients are closely associated to the bacteria Neisseria and that this finding is especially important for Asian patients.

“This discovery is significant because it can change how we treat our bronchiectasis patients with this bacterium. Doctors will now need to think about Neisseria as a potential ‘culprit’ in patients who are worsening despite treatment, and to conduct tests to identify those who may be harbouring this type of bacteria in their lungs.

“We hope that early identification will lead to personalised therapy, and consequently, better disease outcomes for Asian patients with this devastating disease.”

Neisseria bacteria in the home

Aside from linking Neisseria and severe bronchiectasis, the NTU-led research team also detected the presence of the same bacteria in other more common chronic respiratory conditions such as severe asthma and Chronic Obstructive Pulmonary Disease (COPD) – a condition that causes airflow blockage and breathing-related problems.

Using next-generation sequencing technologies, the team also sought to investigate where this bacterium may come from and sampled the homes of bronchiectasis patients with high amounts of Neisseria in their lungs. The researchers found the presence of the bacteria in the home environment, suggesting that the indoor living space and potentially the tropical climate may favour the presence of this bacteria in the Asian setting.

Co-author, Professor Wang De Yun from the Department of Otolaryngology at the Yong Loo Lin School of Medicine, National University of Singapore, said: “It is encouraging to see that we have made headway in identifying the Neisseria bacteria species as the cause of worsening bronchiectasis, the unlikely culprit that was originally not considered to be a threat.

“This comes as a strong reminder that we should not be too complacent when it comes to doing research and exercise more proactiveness in exploring various possibilities, as every seemingly innocent element could be a source of threat to our bodies and overall health.”

The study is published in Cell Host & Microbe.

Image: Detection of Neisseria (N. subflava) in lung tissue from patients with bronchiectasis. Shown in red is the N. subflava detection and shown in blue is the airway cell nuclei.

Credit: Cell Host & Microbe