TYPING NEISSERIA-MENINGITIDIS BY ANALYSIS OF RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS IN THE GENE ENCODING THE CLASS-1 OUTER-MEMBRANE PROTEIN - APPLICATION TO ASSESSMENT OF EPIDEMICS THROUGHOUT THE LAST 4 DECADES IN CHINA

A typing method was developed for Neisseria meningitidis serogroup A b y analysis of restriction fragment length polymorphisms (RFLP) of the class 1 outer membrane protein gene (porA). By using appropriate prime rs, an approximately 1,116-bp fragment of the porA gene was amplified by PCR and then was digested with the restriction endonuclease MspI. T he digestion products were separated on 10% polyacrylamide gels and we re stained with silver. One hundred three clinical isolates of group A N. meningitidis from 17 provinces of China collected over a 26-year p eriod were analyzed. Results of MspI-generated RFLP profiles of PCR-am plified porA genes were compared with those obtained by conventional s erosubtyping. There was a hand of about 400 bp common to all strains e xamined, and the 103 strains of serogroup A resulted in 22 unique RFLP patterns. The differences in bands could be observed mainly in the ra nge of 120 to 280 bp. The smaller fragments were useful in distinguish ing meningococci with the same serosubtype. Three epidemic periods wer e characterized by the presence of three distinct genotypes (a1, a2, a nd a3), accounting for 74.5% of the strains examined (3.88, 26.21, and 44.66%, respectively). Three predominant RFLP patterns were correlate d epidemiologically with cycles of epidemic meningococcal meningitis a nd were well-matched to the predominant serosubtypes (P1.9, P1.7,10, a nd P1.9) that presented at the same prevalence cycles. The genotyping yielded information that allowed strains from one epidemic to be disti nguished from those from another that would have been indistinguishabl e if only serotyping and serosubtyping were available. Therefore, the PCR-RFLP typing method was very useful in the epidemiologic investigat ion of group A meningococcal meningitis.