Neisseria

Neisseria is a genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogens, Neisseria meningitidis and Neisseria gonorrhoeae. Most Neisseria are not pathogenic and are part of the normal flora of the upper respiratory tract.

Taxonomy

The genus Neisseria is named after the German bacteriologist Albert Neisser, who discovered its first representative, Neisseria gonorrhoeae, the pathogen causing the disease gonorrhea. The genus includes commensal organisms, which colonize the respiratory tract, and pathogenic species, such as the aforementioned N. gonorrhoeae and N. meningitidis.

Characteristics

Neisseria species are Gram-negative bacteria, enclosed in a lipid membrane. They are typically diplococci, meaning they occur in pairs, with adjacent sides flattened. They are also aerobic and non-motile. Neisseria species have a unique cell envelope containing an outer membrane and peptidoglycan-associated proteins which are related to their pathogenicity.

Pathogenic species

Neisseria meningitidis

Neisseria meningitidis, often referred to as meningococcus, is a bacterium that can cause meningitis and other forms of meningococcal disease. It is a major cause of morbidity and mortality worldwide.

Neisseria gonorrhoeae

Neisseria gonorrhoeae, also known as gonococcus, is a species of gram-negative diplococci bacteria responsible for the sexually transmitted infection gonorrhea.

Commensal species

In addition to the pathogenic species, there are several species of Neisseria that are commensal, meaning they live on the surface of the body without causing disease. These include Neisseria lactamica, Neisseria cinerea, and Neisseria polysaccharea.

Treatment and prevention

Treatment of Neisseria infections depends on the species and the severity of the infection. Antibiotics are commonly used, but the emergence of antibiotic-resistant strains has complicated treatment. Vaccines are available for some strains of Neisseria meningitidis.