Polymerase chain reaction and direct sequencing of Neisseria gonorrhoeae protein IB gene: partial nucleotide and amino acid sequence analysis of strains S4, S11, S48 (serovar IB4) and S34 (serovar IB5).

A pair of primers were designed for the polymerase chain reaction (PCR) to amplify a 341-base pair fragment of the gene encoding the outer membrane protein IB (PIB) of Neisseria gonorrhoeae. This PCR technique is specific and sensitive, being able to detect gonococcal strains belonging to ten different PIB serovars, but not PIA gonococcus nor other negative control bacteria. PCR products of four representative PIB strains were directly sequenced. Of the three strains belonging to serovar IB4, two (S11 and S48) shared identical nucleotide and amino acid sequences in the PIB region examined. The third IB4 strain (S4) revealed sequences identical to the published IB26 strain (P9). The sequences of strains P9, S4, S11 and S48 were found to differ from those of strain S34 (serovar IB5). The PCR sequencing technique can further differentiate strains belonging to a common serovar and establish clonal relationships among strains. As a molecular epidemiological tool, the PCR-sequencing strategy can augment existing typing methods including serotyping.