Differentiation of Neisseria gonorrhoeae strains by polymerase chain reaction and restriction fragment length polymorphism of outer membrane protein IB genes.

OBJECTIVES To employ polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis for the rapid differentiation of Neisseria gonorrhoeae protein IB (PIB) isolates and to compare its usefulness with the widely accepted auxotype/serovar classification scheme. METHODS The outer membrane protein IB genes of 47 gonococcal isolates belonging to 10 different serovars were amplified by PCR. The approximately 1 kb DNA products were then digested separately with restriction enzymes CfoI and MspA1I, and electrophoresed on agarose gels. RESULTS Cleavage of PIB genes by MspA1I and CfoI differentiated all the N gonorrhoeae strains into five and six PCR-RFLP profiles, respectively. PCR-RFLP was more discriminatory than auxotyping, which classifies the strains into only two auxotypes. Some strains belonging to common serovars could be further differentiated. A combination of PCR-RFLP analysis, auxotyping and serotyping further increased the discrimination of the strains into 34 subtypes. The PCR-RFLP method was easy to perform, reliable, reproducible, and consistent with published nucleotide sequence data. CONCLUSION The PCR-RFLP method can augment auxotyping and serotyping or be used as a preliminary screening tool to differentiate N gonorrhoeae strains in areas where serotyping reagents are not easily available.