The molecular characteristics of Neisseria meningitidis isolated from epidemic cerebrospinal meningitis patients in Guangdong province in past years
Objective To study the molecular characters of porA and porB genes which encode outer membrane proteins (OMP), and predominated clonal complex of Neisseria meningitidis isolates from Guangdong province. Methods Eighteen Neisseria meningitidis isolates from Guangdong province during year 1967 to 2007 were recovered and reconfirmed by API NH biochemical system, and serogrouped by antiserum. The characters of porA and porB gene were analyzed by DNA sequencing. The allele profiles and the sequence types (ST) were determined by multilocus sequence typing (MLST). Based on their allelic profiles, the evolution relationship was analyzed by PHYLIP software. The predominant clonal complex was determined through comparing with the information of reference strains from the PubMLST database. Results For porA gene, type 20 was more frequently in the variable region (VR) 1 and type 9 in VR2 before year 2004. However, for porB gene, type 4 was more frequently in VR Ⅰ, type7 in VR Ⅳ, type 11 in VR Ⅴ,and type 10 in VR Ⅵ, respectively. The multi-types character was presented in VR Ⅴ and VR Ⅵ after2004. VR Ⅶ and VR Ⅷ can not be found among all the isolates except for one W135 isolate in 2007. Among the seven housekeeping genes, the polymorphism of abcZ was the lowest one with 4 allele numbers, while pgm was the highest one with 13 allele numbers. The predominant clonal complex was ST-5 before 2004. The ST-4821 clone complex appeared in 2004 and caused cases every year since then. More important, highly invasive ST-11 clonal complex firstly appeared in Guangdong in 2007. Conclusion The molecular characteristic of OMP genes presents polymorphism for the Neisseria meningitidis isolates from patients in Guangdong province during 1967 to 2007. ST-5 is the predominant clonal complex before 2004 and the highly invasive clonal complex is circulating in recent 3 years. It suggests that the surveillance based on laboratory should be further enhanced. 
 
Key words: 
Neisseria meningitidis;  Molecular character;  Multilocus sequence typing;  Outer membrane protein encoding genes