Typing of Neisseria Meningitidis by Restriction Analysis of the Amplified PorA Gene

We tested a typing system for 54 isolates of Neisseria meningitidis using polymerase chain reaction (PCR) amplification of the porA gene. The isolates were obtained between 1989 and 1994 from cases in Western Australia and Sydney. The PCR product was digested by five restriction endonucleases (AluI, HaeIII, HinfI, RsaI and HpaII) giving a restriction fragment length polymorphism (RFLP) pattern for each isolate. All of the isolates were able to be assigned an RFLP pattern, whereas 24 could be fully serotyped and serosubtyped. The method was rapid and simple to perform and results were easy to interpret. Two outbreaks of invasive meningococcal disease were included in the analysis, one involving an hyperendemic focus of disease and the other characteristic of a point outbreak. The typing system demonstrated the genetic relatedness of isolates from the point outbreak and the genetic diversity among the hyperendemic strains. We conclude that the method is discriminatory and is a useful supplement to serological typing for studying Australian outbreaks of invasive meningococcal disease.