Interactions between bacteria in the human nasopharynx: a scoping review

Emerging evidence indicates that interactions between bacteria shape the nasopharyngeal microbiome and influence respiratory health. This Review uses the systematic scoping methodology to summarise 88 studies including observational and experimental studies, identifying key interactions between bacteria that colonise the human nasopharynx. A range of bacterial interactions were reported in the observational studies, including a variable association between Streptococcus pneumoniae and Haemophilus influenzae, a consistent positive association between S pneumoniae and Moraxella catarrhalis, and a consistent negative association between S pneumoniae and Staphylococcus aureus. Experimental studies largely validated the associations reported in the observational studies and provided insights into the mechanism and direction of interactions. In the context of respiratory health, non-pneumococcal alpha-haemolytic streptococci and the Gram-positive commensals Dolosigranulum and Corynebacterium inhibited respiratory pathogens such as H influenzae, S pneumoniae, M catarrhalis, and S aureus. These findings underscore how bacterial competition and coexistence shape the microbiome composition in this niche. This study has relevance for respiratory health and can be helpful for informing the design of potential microbiota-targeted therapies.