Serological and genetic characterization of meningococcal isolates in Korea.

Meningococcal disease has been regarded as a very rare infection in Korea. Until now, there have been no reports on the serological or genetic characterization of Neisseria meningitidis isolates in Korea. This study was the first report of the serogroup, PorA VR subtype, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and antimicrobial susceptibility of N. meningitidis isolates collected from 2002 to 2003. Of 11 meningococcal isolates, serogroup Y was found to be the most frequent (nine isolates). In addition, one isolate was from serogroup B and one was from serogroup 29E. Four isolates showed a reduced sensitivity to penicillin G. However, all strains tested were susceptible to chloramphenicol, cefotaxime, ciprofloxacin, and rifampin. Among the 11 isolates, seven PorA types were identified. P1.5-1, 2-2 was the most prevalent PorA type, accounting for 55.6% of the serogroup Y isolates. In terms of PFGE patterns, nine isolates of serogroup Y were divided into three clusters, but the isolates shared a high level of PFGE pattern similarity. The serogroup Y isolates were characterized as ST-1625 (five strains) and ST-23 (four). They belonged to the ST-23 complex/Cluster A3. In this study, the ST-23 complex/Cluster A3 was prevalent, with the PorA type P1.5-1, 2-2 accounting for 55.6% of the nine serogroup Y strains. Also, we identified the hypervirulent lineage strain such as ST-6667 of ST-41/44 complex/Lineage 3 in Korea. The results of this study show the need for comprehensive epidemiological surveillance to monitor any changes in the meningococcal disease situation so that prompt intervention can be initiated.