Good bacteria in nasal cavity can influence Covid severity, says study

PUNE: The existing good bacteria in the nasal environment of a Covid-19 positive person can influence the severity of the infection, a study by the city-based National Centre for Cell Science (NCCS) and B J Medical College has revealed.
Scientists say this could also explain why certain individuals infected with SARS-CoV-2 are asymptomatic — the concept being somewhat like the presence of good bacteria in the gut, which help one’s immunity fight infections.
The study has also observed higher abundance of specific opportunistic pathogens in those infected with Covid-19, suggesting that the inflammatory environment caused by the infection leads to an increase in bacterial pathogens that may result in secondary infection. A secondary infection can occur when a different infection, known as the primary infection, makes a person more susceptible to disease.
“The increase in pathogenic bacteria in the nasal microbiome (the microorganisms in a particular environment) of Covid-19 patients is due to the accumulation of mucus, known to favour the growth of these organisms, and hyper-inflammatory environment (extensive inflammation in the body) that supports their growth,” said Avinash Sharma, scientist, NCCS, who led the study.
Sharma told TOI that the increase in various opportunistic pathogens in the nasal environment might also promote the entry of the virus via the route. He said, “There was a reduction in good bacteria, known to have a positive impact on the immune system, in the nasal region of Covid-19 patients. This in turn causes opportunistic pathogens to colonize the site. The study is significant as it can help determine how the virus actually promotes increase in opportunistic pathogens, which may enhance the severity of other diseases.”
As part of the study, researchers collected nasopharyngeal swabs from clinically suspected patients of SARS-CoV-2 infection and their family contacts.
Sharma said it was intriguing to investigate the microbiome shift in the asymptomatic and symptomatic SARS-CoV-2 infected individuals. “Abundance of certain bacteria increased in the nasal environment of symptomatic SARS-CoV-2 patients compared to non-infected ones. Symptomatic and asymptomatic individuals were further classified based on their age groups and gender. We also found a contrasting change in the abundance of microorganisms within the asymptomatic and symptomatic individuals in all the age groups. The difference in existing microbiome could thus also influence the severity of Covid in patients, though this needs further research,” Sharma said.
The study has found that in most cases, the abundance of ‘Streptococcus’ (harmful bacteria) increased, while beneficial bacteria such as Veillonella, Rothia, and Prevotella 7 decreased in infected individuals.
Dr Kaushal Sheth, honorary secretary of The Association of Otolaryngologist of India, told TOI, “The severity of Covid-19 could be influenced by the existing commensal pathogens since these essentially reinforce the mucosal barrier by decreasing the inflammatory reactions in the nasal mucosal lining, thereby preventing the entry of the virus."
Sanjay Pujari from the Indian Council of Medical Research’s national task force on clinical research for Covid-19 and director of the Institute of Infectious Diseases, Pune, told TOI, “The study makes some interesting observations and is first of its kind in India. Its findings on changes in nasal microbiome of Covid patients are likely to lead to the generation of further hypotheses to be tested in a longitudinal follow-up study. That, in turn, will confirm changes occuring in the nasal microbiome in different categories of Covid patients over the course of the illness.”