UTILITY OF RIBOTYPING, RESTRICTION-ENDONUCLEASE ANALYSIS AND PULSED-FIELD GEL-ELECTROPHORESIS TO DISCRIMINATE BETWEEN ISOLATES OF NEISSERIA-GONORRHOEAE OF SEROVAR IA-2 WHICH REQUIRE ARGININE, HYPOXANTHINE OR URACIL FOR GROWTH

Neisseria gonorrhoeae isolates that require arginine-i.e., either citr ulline (C), or ornithine (O)-uracil (U) and hypoxanthine (H) have gene rally been considered to be similar when characterised by auxotype, se rovar and plasmid content. The MICs of penicillin, tetracycline, eryth romycin, spectinomycin, cefoxitin and ceftriaxone for 552 isolates bel onging to serovar IA-2 with these phenotypes were found to be similar. Therefore, restriction fragment length polymorphism analysis of rRNA genes (ribotyping), restriction enzyme (RE) analysis of chromosomal DN A, and pulsed-field gel electrophoresis (PFGE) were evaluated to deter mine whether these isolates could be distinguished by molecular method s. A subset of 27 isolates of N. gonorrhoeae that were OUH-requiring, CUH-requiring or OH-requiring, belonged to serovar IA-2 and carried a 2.6-MDa plasmid, were selected for further study. Based on the RE anal ysis of SmaI-digested genomic DNA, the 27 isolates fell into a single RE pattern, five ribotypes and 17 PFGE profiles which did not correlat e with the specific arginine-requiring subtypes of these isolates. Eac h ribotype varied by the presence of only a single fragment, which was of a different size in each,pattern, and 17 (63 %) of the 27 isolates belonged to ribotype I. PFGE yielded the highest level of discriminat ion with 17 different profiles.