Singapore Scientists Offer Groundbreaking Insights into How Respiratory Microbiomes Shift During Influenza and COVID-19

Medical News: Unveiling the Microbial Communities in Respiratory Health and Disease
Respiratory microbiomes - the diverse colonies of microorganisms residing in the nasal and respiratory tracts - are gaining attention as critical players in health and disease. These microbiomes include bacteria, viruses, and fungi that coexist with their human hosts, influencing immune responses, disease susceptibility, and overall health outcomes. Recent research covered in this Medical News report, has highlighted their pivotal role in respiratory illnesses, particularly in distinguishing between influenza and other respiratory infections. This comprehensive review, conducted by researchers from the Yong Loo Lin School of Medicine, National University of Singapore, offers groundbreaking insights into how respiratory microbiomes shift during illnesses like influenza, COVID-19, pneumonia, and chronic rhinosinusitis (CRS).


Singapore Scientists Offer Groundbreaking Insights into How Respiratory Microbiomes Shift During Influenza and COVID-19

Study Background: Investigating Microbial Dysbiosis
The objective of this systematic review was to explore patterns of dysbiosis - the imbalance of microbial communities - associated with respiratory infections. The research team, including Yunrui Hao, Ying-Jou Lee, Kihan Yap, Miny Samuel, and Vincent T. Chow, analyzed data from 31 studies selected from 2269 articles. Their goal was to identify bacterial markers, changes in diversity, and unique microbiome characteristics linked to influenza and other respiratory illnesses.
 
The review examined the respiratory microbiomes of various cohorts: influenza patients compared to healthy controls, severe versus mild influenza cases, adults versus pediatric patients, and influenza versus other respiratory infections. A key focus was identifying signature bacteria and understanding how these microbial changes correlate with disease severity and outcomes.
 
Key Study Findings: Patterns and Implications
-Signature Bacteria in Influenza
One of the most striking findings was the identification of specific bacterial phyla and genera associated with influenza. Firmicutes and Actinobacteria were notably more abundant in influenza patients compared to healthy controls. At the genus level, Streptococcus, Actinomyces, and Neisseria emerged as significant markers in severe influenza cases. These bacteria are known for their potential to exacerbate respiratory conditions, contributing to complications such as bacterial pneumonia.
 
-Microbial Diversity and Disease Severity
The study revealed a complex relationship between microbial diversity and disease severity. Influenza patients exhibited reduced alpha diversity (a measure of microbial richness and evenness) compared to healthy individuals. This reduction signifies a loss of beneficial commensal bacteria, which play protective roles in maintaining respiratory health. However, paradoxically, severe influenza cases showed increased alpha diversity compa red to mild cases. This increase was attributed to the overgrowth of pathogenic bacteria like Streptococcus and Prevotella, disrupting the normal microbial equilibrium.
 
Beta diversity (the variation in microbial composition between groups) also highlighted significant differences. Healthy controls had markedly distinct microbiomes compared to influenza patients, underscoring how infections disrupt respiratory microbial communities.
 
-Pediatric Versus Adult Microbiomes
Age-specific differences in microbiome composition were another crucial finding. Pediatric influenza patients showed higher levels of Prevotella and Actinomyces, whereas adult patients had an increased abundance of Pseudomonas and Streptococcus. These variations suggest that age-related factors, such as immune system maturity and baseline microbiome composition, influence the response to respiratory infections.
 
-Comparative Analysis with Other Respiratory Infections
Comparing influenza with conditions like pneumonia, COVID-19, and CRS revealed overlapping and distinct microbial patterns. For example, both influenza and pneumonia patients had elevated levels of Streptococcus and Firmicutes, suggesting shared mechanisms of microbial dysbiosis. However, COVID-19 patients exhibited unique increases in Pseudomonas and Proteobacteria, reflecting different host-pathogen interactions.
 
Interestingly, CRS patients showed a predominance of Haemophilus and Proteobacteria, which are less common in influenza. These findings highlight the potential for microbiome profiling to differentiate between respiratory conditions and tailor treatment strategies accordingly.
 
Mechanisms Behind Microbial Dysbiosis
The review explored how influenza alters respiratory microbiomes. Viral infections like influenza can disrupt the epithelial barriers of the respiratory tract, creating opportunities for pathogenic bacteria to colonize and proliferate. Streptococcus and Neisseria, for example, are known to exploit these disruptions, enhancing their adherence to respiratory tissues. This mutualistic relationship between viruses and bacteria may amplify disease severity, leading to complications such as secondary bacterial pneumonia.
 
Additionally, the reduction of beneficial bacteria like Corynebacterium and Lactococcus in influenza patients compromises the microbiome’s stability and its protective effects. These commensal bacteria are crucial for regulating immune responses and preventing the overgrowth of pathogens. Their absence exacerbates the dysbiosis, increasing susceptibility to severe infections.
 
Longitudinal Changes in Microbiomes
One study within the review provided insights into how respiratory microbiomes evolve over the course of influenza. During the early stages of infection, bacteria like Prevotella melaninogenica and Leptotrichia were more abundant. By the later stages, other bacteria, such as Fusobacterium necrophorum, dominated. These temporal changes suggest that the microbiome’s composition is dynamic, influenced by the host’s immune response and the progression of the infection.
 
Clinical Implications: Leveraging Microbiomes for Better Outcomes
The findings from this review underscore the potential of microbiomes as biomarkers for diagnosing and managing respiratory infections. Monitoring microbial patterns could enable early identification of severe cases, guiding timely interventions. For instance, targeting specific bacteria like Streptococcus or restoring beneficial microbes through probiotics might mitigate complications and improve recovery rates.
 
Moreover, microbiome-based therapies could play a role in preventing infections. By promoting a healthy respiratory microbiome, it may be possible to enhance resistance against pathogens and reduce the incidence of illnesses like influenza.
 
Limitations and Future Directions
While this review provides valuable insights, it also highlights the need for further research. Most studies analyzed microbiomes at a single time point, limiting the understanding of longitudinal changes. Additionally, variations in study methods and populations, such as geographic and demographic differences, complicate comparisons.
 
Future studies should adopt longitudinal designs to track microbiome dynamics before, during, and after infections. Larger, more diverse cohorts are also needed to account for variability in microbiome composition across populations. Such research could pave the way for personalized medicine approaches, leveraging microbiome profiling to predict susceptibility and tailor treatments.
 
Conclusions
This comprehensive review sheds light on the intricate relationships between respiratory microbiomes and infections like influenza. The findings reveal distinct microbial patterns associated with disease severity, age, and type of infection. By identifying signature bacteria such as Streptococcus, Actinomyces, and Neisseria, the study provides a foundation for developing microbiome-based diagnostics and therapies.
 
Ultimately, understanding and modulating the respiratory microbiome could revolutionize the management of respiratory infections, reducing their global burden and improving patient outcomes.
 
The study findings were published in the peer-reviewed International Journal of Molecular Sciences.
https://www.mdpi.com/1422-0067/26/2/778
 
For the latest on Microbiome and Microbiota research, keep on logging to Thailand Medical News.
 
Read Also:
https://www.thailandmedical.news/news/link-between-infant-respiratory-microbiome-and-respiratory-syncytial-virus-rsv-severity-uncovered
 
https://www.thailandmedical.news/news/influenza-flu-study-shows-that-targeting-nasal-bacteria-helps-to-block-flu-transmission
 
https://www.thailandmedical.news/news/warning-dysbiosis-induced-by-sars-cov-2-infections-presents-risk-of-antibiotic-resistance