Molecular epidemiology of Neisseria gonorrhoeae in Scotland
The incidence of Gonococcal infection in Grampian region was the highest in Scotland in 1992, 1993 and 1994. Despite a considerable decrease in 1994, it remained more than twice that of the whole country. Grampian also differed from other regions in that 1A isolates were commoner, accounting for around 78%, 73% and 75% of isolates; the 1A-2 serovar was particularly common. The proportion of 1B isolates in Grampian (22%, 27% and 25%) was low compared with the other centres where 1B accounted for around 70% of all isolates (Young & Moyes, 1996). Seventy-six 1992, 1993 and 1994 clinical isolates of various serotypes were obtained from the Scottish Neisseria gonorrhoeae Reference Laboratory including 40 strains from Grampian and 36 strains from Lothian. Genomic DNA was subjected to pulsed-field gel electrophoresis (PFGE) after digestion with low-frequency cleavage (LFC) endonucleases Nhe I and Spe I. The restriction patterns generated were reproducible, stable and easy to read. PFGE was compared to restriction endonuclease analysis (REA) with high-frequency cleavage (HFC) endonuclease Hind III, and 16S rDNA ribotyping with EcoR I. The comparison of phenotypic based typing methods and DNA-based typing techniques to study the 76 N. gonorrhoeae isolates in the present study indicate that the DNA-based methods are more discriminatory. However, the patterns obtained by NheI and Spe I PFGE analysis were easily interpreted, reliable and more discriminatory than those of Hind III REA. The finding of this study clearly demonstrate the potential of PFGE as a high discriminatory tool, as compared to MAb-based serotyping, auxotyping, S/A classification, 16S rDNA ribotyping and REA for studying the molecular epidemiology of gonorrhoea.