Carriage and transmission of neisseria meningitidis
Trotter CL., Maiden MCJ.
© Springer International Publishing Switzerland 2016. Despite the fact that the meningococcus is a pathogen of global significance, causing the severe syndromes of meningitis and septicemia, it is a member of the normal microbiota of the nasopharynx of healthy humans. Indeed, this is the natural habitat of Neisseria meningitidis, and no other reservoir is known to exist for this bacterium. As the process of causing disease does not contribute to person-to-person transmission of meningococci, it is most usefully characterized as an ‘accidental pathogen’ of humans; host invasion is a dysfunctional event for both the microbe and its host, from which neither gains any benefit  (Figure 2.1). Although the significance of the carrier state has been long recognized, it has become increasingly apparent that an understanding of carriage is crucial to an understanding of meningococcal disease and its prevention. Here we shall outline the important features of meningococcal carriage and its study, and their implications for understanding disease.