02:52am Thursday 12 December 2019

Unexpected diversity of the nose


The human body is colonized by bacteria. They live on our skin, in our body’s orifices and throughout our gastrointestinal tract. There they can prevent dangerous germs (pathogens) from colonising and thus protect us against such infections, or they help in digestion. When the immune system is weakened, even the so called harmless germs can become a problem and make us sick. One of these bacteria is Staphylococcus aureus. In almost one third of all people, S. aureus lives in the nose without causing any problems. However, it can be transmitted and be the cause of skin infections, muscular diseases or even life-threatening illnesses such as pneumonia or blood poisoning. Scientists from the Helmholtz Center for Infection Research (HZI) in Braunschweig together with doctors from the University Hospital Münster, have investigated if other bacteria could help in the fight against S. aureus. The scientists explored which bacteria occur in the nose and whether there are differences between carriers of S. aureus and people who do not have the germ. They found a wide range of different types of bacteria in the nose, including some types that appear dominantly in non-carriers. Their results are now published in the scientific journal “International Society for Microbial Ecology”.

The human skin and mucous membranes are colonized by complex bacterial communities that protect us against infection, but occasionally they themselves can become a problem. “Little is known about how complex the composition of bacterial communities of the human body really is” said Dietmar Pieper, director of the Working Group on Microbial Interactions and Processes at the HZI. However, in order to fight infections such as those caused by S. aureus, it is important to understand how the bacteria interact and thus influence each other.

To examine the bacterial communities, the researchers at the HZI together with scientists at the University Hospital Münster analyzed the nasal swabs from 40 randomly selected individuals. The researchers were primarily interested in discovering which bacteria actually live in the nose. To find out, they used culture-independent methods that not only allow the precise examination of large numbers of samples, but also allow the detection of those bacteria that can not be grown or only grow poorly in the laboratory. They achieved this by analyzing a gene that occurs in all bacterial species and has the same function across all bacteria. However, certain regions of this gene differ from species to species and using these so-called variable regions the researchers were able to determine which bacterial species are present in the nose.

The findings were surprising. Of the many different species of bacteria inhabiting the nose, various species have not been described in humans before. In addition, the scientists found many species that can live without oxygen.

Subsequently, the researchers statistically determined that the bacteria can influence each other. The scientists found patterns where some bacterial species frequently occur together and where some bacterial species can not share the same habitat. “We were able to show that when species of the genus Finegoldia were present in the nose, S. aureus was typically absent” said Dietmar Pieper. The reason for this is yet to be elucidated. “This does not mean that S. aureus maybe cleared from the nose by Finegoldia, as this bacteria may also cause infection”. The results highlight the importance of understanding how bacteria colonize and create habitats over the human body and also how they influence each other. From this work the researchers hope to develop future strategies to combat S. aureus infections.

Original article: Wos-Oxley ML, Plumeier O, von Eiff C, Taudien S, Platzer M, Vilchez-Vargas R, Becker K, Pieper DH. A poke into the diversity and associations within human anterior nare microbial communities. The ISME Journal advance online publication, doi:10.1038/ismej.2010.15

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