ARGININE-, HYPOXANTHINE-, URACIL-REQUIRING ISOLATES OF NEISSERIA-GONORRHOEAE ARE A CLONAL LINEAGE WITHIN A NON-CLONAL POPULATION

Multilocus enzyme electrophoresis has been shown that a collection of 101 arginine-, hypoxanthine-, uracil-requiring (AHU(-)) isolates of Ne sseria gonorrhoeae, recovered over a period from the UK and Denmark, w ere of a single electrophoretic type (91% of strains), or differed fro m the predominant electrophoretic type at only a single locus, The str iking uniformity of the AHU(-) isolates, and the correlation between a uxotype, serovar and overall genetic background, contrasts with previo us studies of gonococcal populations (that included very few AHU(-) st rains), and a small sample of non-AHU(-) isolates studied here, which demonstrated a non-clonal population structure and a lack of associati on between auxotype, serovar and genetic background. There was no mark ed difference in the ability of AHU(-) isolates to be transformed with their own DNA, or with DNA from gonococci of other auxotypes, and the relative genetic stability of AHU(-) isolates does not appear to be d ue to a defect in their ability to be transformed. An alternative poss ibility is that AHU(-) gonococci recombine with other lineages, but th at the resulting recombinants are not maintained in the population. Th is would occur, for example, if AHU(-) gonococci competed poorly in mi xed infections, within which effective recombination between lineages occurs, and are usually only transmitted from individuals who are sing ly infected with an AHU(-) strain. The association between AHU(-) gono cocci and asymptomatic infections may lead to an increased rate of tra nsmission of these strains which under this scenario would be needed t o prevent them from being lost from the population.