Use of variable-number tandem repeats to examine genetic diversity of Neisseria meningitidis.

Repetitive DNA motifs with potential variable-number tandem repeats (VNTR) were identified in the genome of Neisseria meningitidis and used to develop a typing method. A total of 146 meningococcal isolates recovered from carriers and patients were studied. These included 82 of the 107 N. meningitidis isolates previously used in the development of multilocus sequence typing (MLST), 45 isolates recovered from different counties in Norway in connection with local outbreaks, and 19 serogroup W135 isolates of sequence type 11 (ST-11), which were recovered in several parts of the world. The latter group comprised isolates related to the Hajj outbreak of 2000 and isolates recovered from outbreaks in Burkina Faso in 2001 and 2002. All isolates had been characterized previously by MLST or multilocus enzyme electrophoresis (MLEE). VNTR analysis showed that meningococcal isolates with similar MLST or MLEE types recovered from epidemiologically linked cases in a defined geographical area often presented similar VNTR patterns while isolates of the same MLST or MLEE types without an obvious epidemiological link showed variable VNTR patterns. Thus, VNTR analysis may be used for fine typing of meningococcal isolates after MLST or MLEE typing. The method might be especially valuable for differentiating among ST-11 strains, as shown by the VNTR analyses of serogroup W135 ST-11 meningococcal isolates recovered since the mid-1990s.