Association of nasopharyngeal Dolosigranulum pigrum & Corynebacterium species w/ post-acute sequelae of SARS-CoV-2 in a longitudinal cohort, 2026,Ward

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Association of nasopharyngeal Dolosigranulum pigrum and Corynebacterium species with post-acute sequelae of SARS-CoV-2 in a longitudinal cohort

Ward, Bradley; Bindels, Laure B.; Balligand, Jean-Luc; Bearzatto, Bertrand; Bommer, Guido; Cani, Patrice D.; De Greef, Julien; Dewulf, Joseph P.; Gatto, Laurent; Haufroid, Vincent; Jodogne, Sébastien; Kabamba, Benoît; Pyr dit Ruys, Sébastien; Vertommen, Didier; Yombi, Jean Cyr; Belkhir, Leïla; Elens, Laure

Abstract
This longitudinal study investigated the differential composition of the nasopharyngeal microbiome in patients presenting different COVID-19 infectious phenotypes and its evolution during convalescence, with a focus on post-acute sequelae of SARS-CoV-2 (PASC) and its potential microbiome-related mechanisms.

Microbiota composition was assessed for a cohort of healthy participants ( n = 25), influenza patients ( n = 24), and patients with moderate ( n = 50) and severe ( n = 57) COVID-19.
Samples were collected at two time points: during the acute infection phase and at approximately 3-month follow-up.
From collected nasopharyngeal swab samples, metagenomics using shotgun sequencing was performed and the microbiota composition was analyzed.

Alpha and beta diversity analyses revealed no significant differences in overall community diversity between patient groups across visits.
However, differential abundance testing identified specific species, such as Dolosigranulum pigrum and various Corynebacterium species, whose profiles correlated with PASC development.
Furthermore, the analysis of microbial co-associations identifies commensal species, including D. pigrum and Corynebacterium species, which are less abundant in patients who develop PASC, consistent with a potential protective role suggested by experimental studies but not proven by our observational data.
Antibiotic use was associated with lower levels of key protective taxa, which may increase susceptibility to PASC in case of superinfection.

These findings highlight the potential importance of the nasopharyngeal microbiome in acute COVID-19 disease outcomes and suggest that preserving or restoring a balanced respiratory microbiome could mitigate the risk of COVID-19 persistent symptoms and PASC development.
Our results may set the stage for future clinical interventions involving probiotics or microbial-derived metabolites to promote respiratory health post-COVID-19.

Importance
This study highlights the importance of bacteria naturally found in the upper respiratory tract, particularly the nasopharynx (the nasopharyngeal microbiome), in shaping how severely COVID-19 affects patients and whether they experience persistent symptoms, also called long-COVID or post-acute sequelae of SARS-CoV-2 (PASC).
By examining microbiome samples from healthy people, influenza patients, and individuals with COVID-19 during acute and convalescent phases, we found that certain commensal bacteria, namely, Dolosigranulum pigrum and Corynebacterium species, were less abundant in individuals who developed long-COVID and more abundant in those who fully recovered.
We also observed that antibiotic treatment was associated with lower abundances of these commensal taxa, in turn coinciding with a higher frequency of PASC.
These findings suggest that the composition of the nasopharyngeal microbiome is associated with recovery trajectories after COVID-19 and motivate future research into treatments aimed toward the microbiome to improve respiratory health following infection.

Web | DOI | PDF | Microbiology Spectrum
 
https://www.eurekalert.org/news-releases/1120278

NEWS RELEASE 17-MAR-2026

Discovery of a bacterium that protects against long Covid​

Peer-Reviewed Publication
UNIVERSITÉ CATHOLIQUE DE LOUVAIN


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According to WHO, approximately 6% of the worldwide population who contract Covid-19 – some 400 million people – go on to develop a long-lasting form of the disease. These figures demonstrate that the persistent form of the disease remains a problem and is a major public health challenge.

In 2021, in the midst of the Covid-19 pandemic, University of Louvain (UCLouvain, Belgium) and its hospital, the Cliniques universitaires Saint-Luc, launched a large-scale study to determine whether it is possible to predict, during the acute phase of infection, the development of long-term symptoms. The ultimate goal is to better understand the underlying mechanisms and, potentially, develop a preventive therapeutic solution.

After five years of research, scientists have discovered the key role played by a bacterium, Dolosigranulum pigrum, that is naturally present in the respiratory microbiome. When present in greater numbers, these bacteria are associated with a reduction in the persistence of symptoms characteristic of long Covid.

Jean Cyr Yombi, Leïla Belkir, and Julien De Greef – UCLouvain professors who are infectious disease specialists at the Cliniques universitaires Saint-Luc – analysed the severity of long Covid symptoms in 156 patients, focusing primarily on severe fatigue, cognitive impairments, and respiratory issues (shortness of breath). Next, UCLouvain professors Laure Elens and Patrice Cani and UCLouvain Louvain Drug Research Institute postdoctoral researcher Bradley Ward analysed in blood samples and nasopharyngeal swabs the molecular signatures associated with this severe form of the disease – a combination of invisible factors that help explain why these symptoms persist in some patients but not in others.

UCLouvain and Cliniques universitaires Saint-Luc researchers stated, “This study suggests that certain so-called protective bacteria in the respiratory microbiome may be associated with improved recovery following viral respiratory infections (such as long Covid or influenza), and that their alteration (particularly in the context of severe infection or non-targeted antibiotic therapy) may influence longer-term clinical outcomes.” In other words, when the bacterium is abundant in the body, it appears to protect against long Covid or severe influenza (through a mechanism that has yet to be elucidated). Conversely, when it is scarce, researchers observe a predisposition to developing a persistent form of the disease.

The good news is that the protective effect of this bacterium was already known in relation to infectious influenza. This new discovery, published in the research journal Microbiology Spectrum, attests to the potentially beneficial role of Dolosigranulum pigrum and will, scientists hope, accelerate research in the field and drive exploration of new therapeutic strategies with a view to developing a probiotic – in the form of a nasal spray, for example – to be taken prior to the winter season, in order to protect the population from severe infectious diseases such as Covid-19 or influenza.

Another key finding of the study is the impact of non-targeted antibiotics on the respiratory microbiome’s ability to defend itself against severe infections. Hence the importance of regulating the use of antibiotics.

This research involved the University of Louvain HYGIEIAconsortium and the Cliniques universitaires Saint-Luc, and was made possible thanks to the support of the Sofina Covid Solidarity Fund and partnerships with the Fondation Saint-Luc, the FNRS (via an emergency research grant) and the WEL Research Institute of the Walloon Region.

JOURNAL​

Microbiology Spectrum

DOI​

10.1128/spectrum.02313-25

METHOD OF RESEARCH​

Randomized controlled/clinical trial

SUBJECT OF RESEARCH​

Human tissue samples

ARTICLE TITLE​

Association of nasopharyngeal Dolosigranulum pigrum and Corynebacterium species with post-acute sequelae of SARS-CoV-2 in a longitudinal cohort

ARTICLE PUBLICATION DATE​

17-Mar-2026
 
The first image shows the significant overlap here between the groups. So while the machine learning can determine there are different groupings its not two distinct and clear groups just another risk factor.
 
The cohort’s mean age was 53.3 years, with 53.2% male and 46.8% female. Average body mass index (BMI) was 26.4. Ethnicities included 77.6% Caucasian, 10.3% African, and the rest Arabic, Asian, Latino-American, Haitian, or unknown. Around 80% were fully vaccinated against COVID-19 before the study. Severe COVID-19 and PASC patients had a higher mean age, a higher proportion of male patients, a higher mean BMI, a higher prevalence of smoking and drinking, and a lower prevalence of full vaccination than those with mild cases or full recovery.
 
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