N. meningitidis is a diplococcus which can normally reside in the throat or nasopharynx of asymptomatic carriers for a few weeks. Humans are the only hosts and transmission occurs by direct contact with infected persons.
The organism may be disseminated through the vascular system, causing meningococcaemia and a petechial rash is observed in the majority of such cases. Meningococci can also penetrate the blood-brain barrier, causing clinical symptoms of meningitis. Meningococcal meningitis can progress rapidly, sometimes resulting in death in a few hours.
The highest incidence of meningococcal infections is seen in infants (6-12 months) and in adolescents.
Due to the severity of infections and the rapid progression of meningococcal septicaemia and meningitis, specimens are dealt with as soon as possible. Normally, a result is available in two to three days.
As PCR is not reliant on viable organisms for detection, this test is an important adjunct to culture especially when patients have received prior antibiotic therapy.