[Analysis of molecular subtypes and microflora structure of Neisseria meningitidis strains isolated in Jiangxi province].

Objective: To study the molecular subtypes and microflora structure of Neisseria meningitidis (Nm) strains isolated in Jiangxi province.

Methods: A total of 123 Nm strains separately isolated from patients, close contacts and health people in 1976-1987 and 2005-2008 were investigated by multilocus sequence typing (MLST) and PorA subtyping, to test the characteristics of gene Nm and sequence porA. Minimum spanning tree was constructed by using BioNumerics software based on data of MLST; and the microflora structure was then analyzed.

Results: The serogroups of 67 Nm strains isolated in 1976-1987 included group A (43 strains), group B (18 strains), group C (1 strains) and group W135 (5 strains); while the serogroups of 56 Nm strains isolated in 2005-2008 included group A (3 strains), group B (7 strains), group C (45 strains) and 1 ungrouped strain. The total 123 Nm strains could be divided into 40 MLST types; while the 46 strains in group A could be divided into 14 MLST types, 29 out of which belonged to ST-3 type, accounting for 63.0% (29/46) as the dominant type. All of the 29 strains were isolated between 1976 and 1987, while 14 strains were isolated from patients, 9 were from close contacts and 6 were from health people. The 46 strains in group C could be divided into 5 MLST types, 41 out of which belonged to ST-4821 type, accounting for 89.1% (41/46). All of the strains were isolated between 2005 and 2008, 6 strains were isolated from patients, 6 were from close contacts and 29 were from health people. The porA gene of the total 123 Nm strains were classified to 32 different types, including 24 different VR1 types and 22 different VR2 types. The dominant PorA type of the prevalent strain (ST-3 type, group A) between 1976 and 1987 was P1.7-1, 10, accounting for 39.1% (18/46) of the strains in group A; while the 18 strains were isolated from 11 patients, 4 close contacts and 3 health people. The dominant PorA type of the prevalent strain (ST-4821 type, group C) between 2005 and 2008 was P1.20, 9, accounting for 46.3% (19/41) of the ST-4821 strains in group C; while the 19 strains were isolated from 1 close contacts and 18 health people. P1.7-2, 14 dominated since 2006, including 22 strains, accounting for 53.7% (22/41) of the ST-4821 strains in group C, isolated from 6 patients, 5 close contacts and 11 health people. There were no dominant PorA type found in group B and all the 5 strains in group W135 belonged to ST-174 and the PorA type was P1.21, 16, isolating from 3 close contacts and 2 health people between 1979 and 1980.

Conclusion: Nm isolated in Jiangxi province showed significant gene polymorphism, as well as predominant lineages existing. In different periods, the prevalent lineages varied a lot, as translating from serogroup A: ST-3:P1.7-1, 10 to serogroup C: ST-4821:P1.7-2, 14 nowadays.