Food-based probiotic may inhibit pneumonia-causing bacterial growth

A probiotic found in foods such as yoghurt and miso soup has been found to inhibit the development of a pathogen that causes middle ear infections in children and pneumonia, a study has shown. 

The bacterial type, Corynebacterium accolens (C. accolens) is primarily found in the human gut, nose and skin. Studies revealed it could inhibit Streptococcus pneumoniae (S. pneumoniae), a common and infectious bacterial species and a pathogen that can lead to middle ear infections and meningitis.

S. pneumoniae is also responsible for septicaemia and otitis media cases seen in children and adults worldwide. The World Health Organisation (WHO) estimates that each year S. pneumoniae leads to more than one million deaths, the majority of which occur in developing countries in children under the age of five.

New data published in the American Society for Microbiology indicated the Corynebacterium species were abundant in children free of S. pneumoniae.

C. accolens, a harmless lipid-requiring species, was found to inhibit pneumococcal growth. This inhibition depended on LipS1, an enzyme necessary for C. accolens growth. The researchers from the Forsyth Institute and Vanderbilt University believed C. accolens released oleic acid, which inhibited S. pneumococcus.

Probiotic-rich food sources

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Foods such as yoghurt contain high levels of probiotic cultures that are beneficial for gut health and overall well-being. (Image:iStock.com) (Arina Habich)

Probiotic bacteria such as C. accolens have been widely researched for immune-boosting properties, as well as their ability to help fight gut-related diseases such as inflammatory bowel syndrome and Crohn’s disease.

As well as yoghurt and miso soup, foods such as Kefir, a yogurt-like drink created by fermenting milk, and Kombucha, a fermented sweet black tea with yeast and bacterial culture, contain high levels of probiotic cultures that are beneficial for gut health and overall well-being.

Other fermented food such as sauerkraut, kimchi, a traditional Korean side dish made of various veggies and seasonings; and pickles also contain probiotic benefits. 

Study details

Led by Dr Katherine Lemon, the researchers found C. accolens was overrepresented in the noses of children that were not colonised by S. pneumoniae, which is commonly found in children’s noses and can cause infection.

In laboratory research, the team further discovered that C. accolens modified its local habitat to inhibit the growth of S. pneumoniae by releasing antibacterial free fatty acids (FFA). The team went on to identify the C. accolens enzyme, TAG lipase, as a key facilitator of this process.

“It remains unknown whether other Corynebacterium spp. inhibit pneumococcal growth via the release of antibacterial FFAs and/or via an as-yet-undiscovered alternative mechanism,” said the study.

“Further, future investigations will determine what species of Corynebacterium are most commonly found in the nasal microbiota of children 6 months to 7 years of age, as it is not yet known how common natural C. accolens nasal colonisation is in this age group.”

Future research

The researchers also theorised that treating the surfaces of human body sites as individual ecosystems implied the existence of a complex network of both microbe-microbe and microbe-host interactions.

“Based on our findings, we predict that on human surfaces C. accolens alters the local host surface environment in a manner that can partially shape the composition of nasal and skin microbiota and by helping to protect against colonisation by pathogens, such as S. pneumoniae.”

The researchers concluded C. accolens could have a role as a beneficial bacterium to control pathogen colonisation but acknowledged more research was needed.

They added that a greater understanding of the molecular mechanisms underlying interactions involving Corynebacterium species would facilitate the development of alternative approaches to interfere with pathogenic colonisation and/or infection.

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Source: American Society for Microbiology

Published online ahead of print, doi: 10.1128/mBio.01725-15

“Corynebacterium accolens Releases Antipneumococcal Free Fatty Acids from Human Nostril and Skin Surface Triacylglycerols”

Authors: Lindsey Bomara, Silvio D. Brugger, Brian H. Yost, Sean S. Davies, Katherine P. Lemon