page_title: Neisseria
section_title: Pathogens
hierarchical_section_title: Neisseria / Classification / Pathogens
caption_attribution_description: English: Maximum likelihood Neisseria species tree based on concatenating the DNA sequences of all 896 core Neisseria genes. From Marri PR, Paniscus M, Weyand NJ, Rendón MA, Calton CM, Hernández DR, et al. (2010) Genome Sequencing Reveals Widespread Virulence Gene Exchange among Human Neisseria Species. PLoS ONE 5(7): e11835. https://doi.org/10.1371/journal.pone.0011835
context_page_description: Neisseria is a large genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogens, N. meningitidis and N. gonorrhoeae. Most gonococcal infections are asymptomatic and self-resolving, and epidemic strains of the meningococcus may be carried in >95% of a population where systemic disease occurs at <1% prevalence.
  Neisseria species are Gram-negative bacteria included among the proteobacteria, a large group of Gram-negative forms. Neisseria diplococci resemble coffee beans when viewed microscopically.
context_section_description: Species of this genus (family Neisseriaceae) of parasitic bacteria grow in pairs and occasionally tetrads, and thrive best at 98.6 °F (37 °C) in the animal body or serum media.
  The genus includes:
  N. gonorrhoeae (also called the gonococcus) causes gonorrhea.
  N. meningitidis (also called the meningococcus) is one of the most common causes of bacterial meningitis and the causative agent of meningococcal septicaemia.
  These two species have the ability of 'breaching' the barrier. Local cytokines of the area become secreted to initiate an immune response. However, neutrophils are not able to do their job due to the ability of Neisseria to invade and replicate within neutrophils, as well avoiding phagocytosis and being killed by complement by resisting opsonization by antibodies, which target the pathogen for destruction.  Neisseria species are also able to alter their antigens to avoid being engulfed by a process called antigenic variation, which is observed primarily in surface-located molecules. The pathogenic species along with some commensal species, have type IV pili which serve multiple functions for this organism.  Some functions of the type IV pili include: mediating attachment to various cells and tissues, twitching motility,  natural competence, microcolony formation,  extensive intrastrain phase, and antigenic variation.
  Neisseria bacteria have also been shown to be an important factor in the early stages of canine plaque development.
caption: Phylogenetic tree of selected Neisseria species, based on concatenating the DNA sequences of all 896 core Neisseria genes, from Marri et al. 2010[3]
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