Presence of Dolosigranulum pigrum in the nasopharynx and its relationship with respiratory health status in paediatric population

Background: Respiratory tract infections range from asymptomatic colonisation to an invasive disease. Recent studies suggest that nasopharyngeal microbiota may influence this variability. Emerging evidence points to Dolosigranulum pigrum, a nasopharyngeal commensal, as a potentially protective bacterium. This study aimed to identify variables associated with the presence of D. pigrum in the nasopharynx of children with varying respiratory health statuses. Methods: Nasopharyngeal aspirates were collected from children 0.1% of total sequences obtained by 16S rRNA gene sequencing. Variables included sex, breastfeeding, delivery mode, S. pneumoniae carriage, respiratory viruses and clinical features. Results: Among 140 children (73 males, 67 females), D. pigrum was detected in 79 (56.4%): 44/65 in the healthy group; 26/48 of viral and 9/27 IPD cases. Multivariate analysis revealed significant associations with health status and sex. Healthy children were more likely to carry D. pigrum than IPD cases (44/79 vs. 26/79; p = 0.028). Males were more frequently D. pigrum carriers than females (48/79 vs. 31/79; p = 0.033). Conclusion: D. Pigrum was associated with respiratory health, being more prevalent in healthy children, and showed potential sex-related differences.