Epidemiology of gonorrhoea: serogroup, antibiotic susceptibility and auxotype patterns of consecutive gonococcal isolates from ten different areas of Sweden.

Consecutively isolated gonococcal strains from 10 representative geographical areas in Sweden were serogrouped according to the previously described W antigen class. The majority of the strains were antibiotic susceptibility tested and approximately one fourth of them were auxotyped. Statistically significant differences of the serogroup patterns were demonstrated between the 2 largest towns, which represented highly urbanized areas where serogroup W II dominated, and the middle sized towns with adjoining rural districts, where serogroup W I dominated. The serogroup patterns of the strains isolated in 3 university towns were representative for Sweden as a whole. Statistically significant differences were demonstrated between urban and rural areas with regard to the susceptibility of gonococci to beta-lactam antibiotics. About 95% of serogroup W I strains were highly sensitive to ampicillin whereas about 65% and 90% of W II and W III strains, respectively, showed decreased susceptibility. The majority of the auxotyped strains belonged to 4 main types: Pro-, Pro-Arg-Ura-, AHU- and prototrophic. The majority of the AHU- strains belonged to serogroup W I and were highly susceptible to beta-lactam antibiotics and tetracycline. Many of the Pro-Arg-Ura-strains belonged to 2 particular subserogroups within serogroup W II and showed increased resistance to beta-lactam antibiotics. Serological classification of gonococci by co-agglutination is a simple and rapid technique without need of special equipment. It could serve 2 purposes: 1) as a confirmation test for gonococci cultured from clinical specimens; 2) for serogrouping of gonococcal isolates to study the epidemiology of gonorrhoea with regard to geographical areas, race, sexual preference, treatment failure and other demographic and medical factors.