Microorganisms and Their Role in Humans

Microorganisms are known to inhabit different parts of the human body. While the organisms get a place to live and nutrients to feed on, the human hosts might or might not benefit from their presence. When they benefit, it is because the organisms help prevent inflammations and support the immune system. However, some microorganisms (both bacteria and virus) can be harmful, causing inflammations leading to disorders. These different kinds of microorganisms and their role in the gut are well known. Recent studies show how based on their presence in respiratory airways, different respiratory disorders may occur.

Development of Healthy Nasal Microorganism Composition in Early Childhood

The upper respiratory tract, starting at the nostrils, is the entry point to microorganisms. By the time we are young adults, a healthy diverse composition of microorganisms occupies the upper respiratory tract in most people. This composition in children varies drastically from birth to infant stage. Few weeks after they are born, in healthy babies, the back of the nose is predominantly occupied by two species of bacteria called Corynebacteriaceae and Staphylococcaceae. By 24 months, the population of these species reduce, and different bacteria populate. There are also differences in organisms present based on the season. The authors of the article believe this occurs due to seasonal infections from harmful bacteria which disturb the healthy composition of microorganisms. Lactobacillacea, though present in smaller quantities, also help prevent infections and disorders.

Overall, these bacteria are associated with protecting the child against respiratory infections in later childhood. The main ways these organisms help is by:

1. occupying sites in the respiratory tract and not giving space to the harmful bacteria,
2. producing inhibitory molecules or depleting nutrients to prevent the growth of the pathogens.

Shift in the Healthy Composition of Microorganisms Causes Respiratory Disorders

In general, lower diversity of microorganisms is associated with inflammation of the mucous membrane (rhinitis) and wheezing. Compared to healthy infants, it was observed that children with rhinitis or wheezing had a lower abundance of bacteria like Corynebacteriaceae and Staphylococcaceae. These bacteria usually prevent the harmful bacteria from colonizing by using different techniques.

Instead of these healthy bacteria, if the airway is populated with harmful bacteria that cause inflammation, the children had a higher risk of wheezing or asthma later in childhood. A few studies (Bisgaard et al.; von Linstow et al.; Tang et al.) showed that one-month-old children who had flu-like bacteria but did not show symptoms subsequently had acute or chronic wheezing in the first 2 years of life. In another study, 7- to 9-week-old children with an abundance of Streptococcus bacteria were associated with chronic wheezing by 5 years. Therefore, the establishment of harmful bacteria in the respiratory tract as babies could predispose the children to rhinitis and wheezing in early childhood.

How Do Harmful Pathogens Cause Mucous Inflammation and Wheezing?

The bacteria multiply and grow into thin films. The harmful pathogens coordinate and intersperse themselves in these films, making them stronger and resistant to antimicrobial agents. They may also release molecules that makes them adhere better. Further, they induce an inflammatory response in the host by activating the immune system. Children with this inflammatory response were shown to be at a higher risk of asthma at the age of 7 years.

Role of Viruses and Conclusion

Viruses are also part of the microorganisms in the respiratory tract. Currently, only the harmful viruses causing acute respiratory tract infections have been studied in detail. While causing mucous inflammation and wheezing during the infection, they also increase the risk of children getting recurrent wheezing later in childhood. The benefits of viruses that attack bacteria have not been well studied yet.

Together, we learn that the composition of the bacteria and virus from the newborn to the infancy and toddler stage can play a significant role in respiratory health in later childhood. Therefore, more research should be done to understand details of how the microorganisms function and to help devise methods to reduce the burden of an inflamed mucous membrane, wheezing or asthma.