Pathogenic Neisseriae
Neisseria meningitidis (meningococcus) and Neisseria gonorrhoeae (gonococcus) are the causative agents of epidemic meningitis and gonorrhoea, respectively. Both are Gram-negative bacteria that specifically infect humans, although they prefer to inhabit distinct human mucosal niches and cause markedly different diseases. One important difference between these pathogens is that almost all clinically important N. meningitidis strains are encapsulated, whereas N. gonorrhoeae strains lack capsule biosynthetic genes. N. meningitidis is a frequent asymptomatic colonizer of the human upper respiratory tract, and most adults are resistant to infection through acquired immunity. However, in susceptible individuals N. meningitidis can cause serious blood and brain infections that are usually manifested as meningitis and septicaemia. It also seems that meningococcal strains vary in their ability to cause sporadic or epidemic outbreaks. The outcomes of meningococcal infection may be devastating and, in the absence of timely intervention, can lead to neurological disorders and death. N. gonorrhoeae is a sexually transmitted pathogen that primarily infects the urogenital tract, giving rise to intense local inflammation and a range of clinical manifestations. A signature property of the two pathogens is their ability to modulate their surface antigenic make up with remarkable speed. This is the basis of their success as human-specific pathogens, as constant surface modulation and point mutations enable the bacteria to evade human immune mechanisms. Extensive surface variation also poses a substantial problem in developing effective vaccines against several strains of N. meningitidis and against N. gonorrhoeae. Although multicomponent vaccines are being developed, the available vaccines fall short of combating all virulent strains.
Pathogenic neisseriae: surface modulation, pathogenesis and infection control. Nature Reviews Microbiology 7, 274 (2009). doi:10.1038/nrmicro2097
Although renowned as a lethal pathogen, Neisseria meningitidis has adapted to be a commensal of the human nasopharynx. It shares extensive genetic and antigenic similarities with the urogenital pathogen Neisseria gonorrhoeae but displays a distinct lifestyle and niche preference. Together, they pose a considerable challenge for vaccine development as they modulate their surface structures with remarkable speed. Nonetheless, their host-cell attachment and invasion capacity is maintained, a property that could be exploited to combat tissue infiltration. With the primary focus on N. meningitidis, this review examines the known mechanisms used by these pathogens for niche establishment and the challenges such mechanisms pose for infection control.
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Tags: Bacteria, Biology, disease, Health, Medicine, Microbiology, Science
