Molecular typing of non sero-groupable Neisseria meningitidis in China

Objective To understand the molecular typing characteristics of 104 non sero-groupable (NG) Neisseria meningitidis strains in China. Methods A total of 104 NG N.meningitidis strains isolated in 2005-2011were characterized by multilocus sequence typing (MLST). Genogroups (A, B, C, W, E, X, Y, Z, H, I, L, K and cnl) were determined by PCR. Results The 104 NGN. meningitidisstrains included capsule null locus (cnl) strains (n=36), genogroup B strains (n=20), genogroup C strains (n=14), genogroup W strains (n=9), genogroup E strains (n=9), genogroup X strains (n=3) and genogroup Y strains (n=3). There were 10 strains which could not be genogrouped. No NG isolates belonging to other genogroups were identified. By MLST analysis, 104 NG N.meningitidis were identified to belong to 45 sequence types (ST) clonal complex, 14 of which were new sequence types; 17 sequence types can be grouped into 7 ST clonal complex (n=65); cnlstrains all belonged to ST-198 complex. The predominant ST complex of genogroup B and genogroup C was ST-4821, and ST-11, ST-174 were predominant in ST complex of genogroup W strains. Conclusion The NG N. meningitidis strains in China showed significant gene polymorphism, and the ST-198 complex strains were all identified as cnl strains.