Availability of polyamines affects virulence and survival of Neisseria meningitidis

Neisseria meningitidis is a Gram-negative human-restricted pathogen that asymptomatically resides in the human respiratory tract. Meningococcal meningitis and sepsis both are caused by N. meningitidis. The bacterium must adhere to host epithelial cells in order to colonize effectively. The factors that determine the initial attachment to the host and dispersal, are not well understood. Metabolites released by the host may aid in meningococcal colonization and dissemination. Polyamines are aliphatic polycations that assist in cell survival and proliferation. The virulence properties of N. meningitidis after exposure to polyamines were investigated. Adhesion to nasopharyngeal epithelial cells increased in the presence of spermine. Also, the relative expression of adhesin, pilE increased in the presence of spermine. Further, relative expression of ctrA, ctrB and lipB was upregulated in the presence of spermidine, indicating increased capsule formation. Upregulated capsule synthesis of N. meningitidis in the presence of spermidine allows it to survive in murine macrophages. The study suggests the importance of the extracellular pool of polyamines in promoting virulence in N. meningitidis .