Effect of respiratory tract co-colonizers on initial attachment of Neisseria meningitidis.

Respiratory tract is a complex system comprising of unique microbiota inhabitants. Neisseria meningitidis, Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa and Klebsiella pneumoniae are few prevalent bacteria in the community composition during lung infections. Although, N. meningitidis resides asymptomatically in nasopharynx of the human host, it can cause fatal infections like meningitis. However, factors affecting transit from carriage to symptomatic infection are not well understood. Various host metabolites and environmental conditions affect the virulence of bacteria. Here, we report that presence of co-colonizers significantly reduces the initial attachment of N. meningitidis to A549 nasopharyngeal epithelial cells. Further, significant decrease in invasion to A549 nasopharyngeal epithelial cells was observed. Moreover, survival in J774A.1 murine macrophage also increases significantly when conditioned media (CM) from S. pyogenes and L. rhamnosus is used for culturing N. meningitidis. The increase in survival could be attributed to increased capsule synthesis. The gene expression studies revealed increased expression of siaC and ctrB in CM prepared from the growth S. pyogenes and L. rhamnosus. Overall, the results suggest change in the virulence of N. meningitidis is assisted by lung microbiota.