Exploring respiratory viral pathogens and bacteriome from symptomatic SARS-CoV-2-negative and positive individuals
Authors: Nema Vijay , Jadhav Sushama , Waghmode Rushabh B , Potdar Varsha A. , Choudhary Manohar Lal 
Published: May 2024

In the COVID pandemic era, increased mortality was seen despite some unknown etiologies other than SARS-CoV2 viral infection. Vaccination targeted to SARS-CoV2 was successful due to infection caused by pathogens of viral origin based on symptomatology. Hence, it is essential to detect other viral and bacterial infections throughout the initial wave of the COVID-19 disease outbreak, particularly in those suffering from a symptomatic respiratory infection with SARS-CoV-2-negative status. This study was planned to explore the presence of bacterial and other respiratory viruses in symptomatic patients with SARS-CoV2-positive or negative status. The study selected128 patient’s samples out of 200 patients’ samples (100 at each time point) collected for routine SARS-CoV-2 detection schedule in December 2020 and June 2021. Considering the seasonal changes responsible for the occurrence of respiratory pathogens, we finalized 64 SARS-CoV-2 tested patients with 32 SARS-CoV-2-negatives and 32 SARS-CoV-2-positives from each collection time to examine them further using real-time PCR for the presence of other viral species and bacterial infection analyzing 16S rRNA metagenome supporting to cause respiratory infections. Along with various symptoms, we observed the co-infection of adenovirus and influenza B(Victoria) virus to two SARS-CoV-2-positive samples. The SARS-CoV-2-negative but symptomatic patient showed Rhinovirus (7/64 i.e. 10.9%) and Influenza (A/H3N2) infection in 4 patients out of 64 patients (6.25%). Additionally, one SARS-CoV-2-negative patient enrolled in June 2021 showed PIV-3 infection. Influenza A/H3N2 and Adenovirus were the cause of symptoms in SARS-CoV-2-negative samples significantly. Thus, the overall viral infections are considerably higher among SARS-CoV-2-negative patients (37.5% Vs 6.25%) compared to SARS-CoV-2-positive patients representing respiratory illness probably due to the abundance of the viral entity as well as competition benefit of SARS-CoV-2 in altering the imperviousness of the host. Simultaneously, 16S rRNA ribosomal RNA metagenomenext-generation sequencing (NGS) data from the same set of samples indicated a higher frequency of Firmicutes, Proteobacteria, Bacteroidota, Actinobacteriota, fusobacteriota, Patescibacteria, and Campilobacterotaphyla out of 15 phyla, 240 species from positive and 16 phyla, 274 species from negative samples. Exploring co-infecting respiratory viruses and bacterial populations becomes significant in understanding the mechanisms associated with multiple infecting pathogens from symptomatic COVID-positive and negative individuals for initiating proper antimicrobial therapy.

Author Summary

Frequent transfer of SARS-CoV-2 events has resulted in the emergence of other viral infections along with several evolutionarily separate viral lineages in the global SARS-CoV-2 population, presenting significant viral variants in various regions worldwide. This variation also raises the possibility of reassortment and the creation of novel variants of SARS-CoV-2, as demonstrated by the COVID pandemic in all the waves, which may still be able to cause illness and spread among people. Still unclear, though, are the molecular processes that led to the adaption of other viral and bacterial pathogens in humans when a human SARS-CoV-2 virus was introduced. In this study, we identified the presence of various other viral infections and bacterial content in symptomatic COVID-19-positive and negative patients, as evidenced by the data obtained using next-generation sequencing of 16S rRNA metagenome and real-time PCR detection technologies. Symptoms might have been induced by bacterial content and various viral entities other than the SARS-CoV-2 viral infection in the COVID-negative population, indicating its importance in detecting and initiating appropriate therapy to recover from all other infections.