Pneumonia caused by bacteria that releases popular household cleaning agent

2 Sep 2019

Image: © Sergey/

Researchers have found that pneumonia develops as a result of bacteria that are releasing hydrogen peroxide, otherwise known as bleach.

The battle between bacteria and our immune system has been highlighted in new research published to Nature Communications. Writing in the journal, a team from Umeå University and Stockholm University in Sweden revealed that bacteria use hydrogen peroxide to weaken the immune system, resulting in the development of pneumonia.

This chemical is a key component of bleaches used for cleaning homes as well as teeth whitening.

“By using hydrogen peroxide to defeat the immune system, you could say that the bacteria are fighting fire with fire,” said Nelson Gekara, who led the research.

“The body itself also produces hydrogen peroxide as a defence against the bacteria. Therefore, it was surprising to see that many types of bacteria actually use the same substance to overcome the body’s defences.”

The focus of this research was on the Streptococcus pneumoniae, the most common bacterium responsible for pneumonia as well as meningitis and severe sepsis. Because of its additional threat of opening the door for other microbes to attack the body, it is considered one of the most deadly in the world.

This is despite the fact that many people have the bacterium in their upper respiratory tract as part of the normal flora without falling ill or even knowing about it. This makes it important to better understand its effects on the body’s immune system.

Unexpected counter

As with any invading microbe, their goal is to live in the body for as long as possible without triggering the immune system to respond. In the case of pneumococcus, the bacterium targets the key component of the immune system: inflammasomes.

When the bacterium comes into contact with these protein complexes, it releases large quantities of hydrogen peroxide, inflaming inflammasomes and weakening the immune system.

In mice models, the research team used altered bacteria that produced less hydrogen peroxide. This showed that they were unable to inactivate inflammasomes and therefore elicited a faster inflammatory response, which effectively cleared the bacteria from mouse lungs.

Additionally, it was possible to inoculate the mice using a special enzyme called catalase that breaks down hydrogen peroxide.

“One of the best known substances with the ability to neutralise hydrogen peroxide and that could hence boost anti-bacterial immunity are vitamins such as vitamin C found in fruits,” Gekara said.

“Perhaps the old adage ‘an apple a day keeps the doctor away’ is not off the mark.”

Colm Gorey was a senior journalist with Silicon Republic