Detection of Neisseria meningitidis in tonsils varies in relation to the frequency of invasive disease

Cultures from nasopharyngeal swabs underestimate the carriage of Neisseria meningitidis. The presence of a broad range of bacteria and of N. meningitidis groups B and C, respectively, in tonsils from 26 individuals from Oxford (England) and 72 from Zurich (Switzerland) was examined employing real-time polymerase chain reaction (PCR) assays. The detection limit of each PCR system was DNA from one bacterial cell per reaction. Tonsilar DNA did not inhibit amplification of meningococcal gene sequences and N. meningitidis was detected in tonsils exposed to the bacterium. Although in both sets of patients other bacteria were detected, N. meningitidis groups B and C were only found in tonsils from Oxford where the incidence of invasive meningococcal disease is much higher than in Zurich. These observations suggest that PCR-based methods could be used for the assessment of meningococcal carriage and that difference in disease incidence could be explained by different transmission rates in the community. © 2003 Elsevier B.V.