Mucus Is a Key Factor in Neisseria meningitidis Commensalism

The work presented by Audry et al. (M. Audry, C. Robbe-Masselot, J.-P. Barnier, B. Gachet, et al., mSphere 4:e00494-19, 2019, https://doi.org/10.1128/mSphere.00494-19) gives new insight into the interactions of Neisseria meningitidis and the human nasopharynx. Using an air interface tissue culture model of a polarized, mucus-secreting epithelium, Audry et al. demonstrate that N. meningitidis bacteria do not commonly invade epithelial cells. Rather, they are trapped in the mucus layer, where they are protected from dessication. In this model, meningicocci fail to elicit a pro-inflammatory immune response and show growth effects in response to another nasopharyngeal colonizer, Streptococcus mitis. These findings prompt new questions about pathobiont behaviors, the role of mucus in bacterium-host interactions, and modeling human infection.