Neisseria gonorrhoeae and Neisseria meningitidis are Gram-negative diplococci (kidney bean-shaped) with flattened sides. They are characteristically found inside polymorphonuclear leucocytes. They are non-sporing, non-motile, and oxidase positive. They have exacting growth requirements and do not grow on ordinary media. Growth occurs on media enriched with blood or serum like Chocolate Agar, Thayer Martin Agar, and Modified New York City Medium.
The major structural difference between N. meningitidis (meningococci) and N. gonorrhoeae (gonococci) is the presence of a capsule. Meningococci have a thick polysaccharide capsule, whereas gonococci do not. In the laboratory, the differentiation between Neisseria meningitidis and Neisseria gonorrhoeae is made based on sugar fermentation: meningococci ferment maltose whereas gonococci do not.
Some of the notable differences between them are:
| Characteristics | Neisseria gonorrhoeae (Gonococci) | Neisseria meningitidis (Meningococci) |
| Capsule | No polysaccharide capsule | Yes (has a prominent polysaccharide capsule and is divided into 13 serologic groups based on capsular antigens) |
| Pili | Yes (one of the most important virulence factors; nonpiliated strains are avirulent) | Yes |
| Portal of Entry | Genital | Respiratory |
| Disease | Male: urethritis, proctitis Female: endocervicitis, PID (contiguous spread), arthritis, proctitis Infants: ophthalmia neonatorum Otitis media Sinusitis Bronchitis and bronchopneumonia in elderly patients with COPD | Meningitis and meningococcemia |
| Glucose Fermentation | Yes | Yes |
| Maltose Fermentation | No | Yes |
| β-Lactamase Production | Common | Rare (Penicillin G is the treatment of choice for meningococcal infection) |
| Vaccine available | No | Yes (conjugate vaccine and unconjugated vaccine are available) |
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