Neisseria meningitidis, an agent of bacterial meningitis, is carried by 70% of the healthy population, where it forms biofilms in the human oral and nasopharynx. A biofilm is an aggregate of surface-associated bacteria enclosed in an extracellular polymeric substance matrix, often associated with increased levels of resistance to antibiotics and genetic exchange. N. meningitidis is closely related to other commensal Neisseria species, N. mucosa, and N. cinerea, that colonize in the same niche but do not cause disease. It is currently unknown whether these commensal species form biofilms. Our research characterizes biofilm formation by commensal species, N. mucosa, and N. cinerea. We employed both a static and a dynamic method to measure biofilm formation. We used undisturbed cultures in 96-well plates for the static method and plastic beads in a shaking tube for the dynamic method. Biofilms are revealed by crystal violet staining and by counting colonies, in the respective methods. Our research is the first to demonstrate biofilm formation by a commensal Neisseria species. In the future, we will further characterize the biofilms and determine whether commensal Neisseria species display increased resistance to antibiotics when in a biofilm vs free-floating cells.
