Phenotypic and genotypic approaches to characterization of isolates of Neisseria meningitidis from patients and their close family contacts

Characterization of isolates of Neisseria meningitidis obtained from patien ts with meningococcal disease or from pharyngeal swabs of asymptomatic carr iers can be achieved by several approaches which provide different levels o f discrimination. A total of 45 gram negative, oxidase-positive diplococcus strains isolated from 15 individuals with meningococcal disease and 30 of their family contacts were examined by three approaches: serological typing , multilocus enzyme electrophoresis (MLEE), and multilocus sequence typing (MLST), For 10 of the 15 patient and contact groups, all of the isolates we re confirmed as meningococci, and the bacteria obtained from the patients a nd contacts, including their mother or principal caregiver in the case of c hildren, were indistinguishable by all three methods. In the remaining five groups the isolates from the patients were distinct from those recovered f rom the contacts, and in three examples, in two separate groups, the contac ts were shown by MLST to be carrying strains of Neisseria lactamica, The da ta obtained from the three techniques were consistent, although complete se rological typing was possible for only a minority of isolates. Both MLEE an d MLST established the genetic relationships of the isolates and identified members of known hypervirulent lineages, but MLST was faster than MLEE and had the additional advantages that it could be performed on noninfective m aterial distributed by mail and that the results from different laboratorie s could be compared via the internet (http://mlst.zoo.ox.ac.uk).