CHARACTERIZATION OF NEISSERIA-MENINGITIDIS BY POLYMERASE CHAIN-REACTION AND RESTRICTION-ENDONUCLEASE DIGESTION OF THE PORA GENE

Subtype classification based on the use of monoclonal antibodies to th e class 1 outer membrane protein combined with techniques such as mult ilocus enzyme electrophoresis remains the standard method of character izing isolates during outbreaks of invasive meningococcal disease. We developed a rapid typing method based on the restriction fragment leng th polymorphisms (RFLPs) within the polymerase chain reaction (PCR) pr oduct of the porA gene, which encodes the class 1 outer membrane prote in, reflecting genotypic rather than phenotypic variability between st rains. Forty-five isolates of invasive Neisseria meningitidis obtained from October 1990 to April 1992 were studied after randomization and coding. Included among these were isolates from a local outbreak that resulted in a mass vaccination program. PCR amplification for each iso late was followed by restriction digestion with the following enzymes in the indicated sequence: HaeIII, RsaI, HinfI, HpaII, and AluI. Eight een different patterns were demonstrated on the basis of RFLPs, wherea s only seven groups were identified after standard subtyping. The most common isolate identified by serosubtyping was serogroup C, serotype 2a, subtype P1.2 (C:2a:P1.2) (38%). Thirteen (76%) of these group C is olates shared a common RFLP pattern after digestion with the five rest riction enzymes. We were able to further differentiate strains of C:2a :P1.2 with electrophoretic type 5 from electrophoretic types 1, 9, and 15 that occurred during an apparent outbreak. We were also able to ch aracterize 15 isolates (33%) which could not be subtyped with monoclon al antibodies. Our method offers a convenient alternative to standard subtyping procedures and is particularly useful in outbreak situations in which rapid characterization of N. meningitidis is essential so th at rational public health policy regarding preventative measures can b e formulated.