Antibiotic susceptibility of Neisseria gonorrhoeae in relation to serogroups

Susceptibility testings, by means of the agar-dilution method, were performed on nine antibiotics of 138 non-PPNG (beta-lactamase-producing = PPNG) strains, 17 of which originated from Thailand, and 88 PPNG isolates. The gonococcal strains were sero-grouped by the co-agglutination method and classified among the sero-groups W I, W II or W III. Statistically significant differences in antibiotic susceptibility between non-PPNG strains of the three sero-groups could be demonstrated with strains belonging to sero-group W I as the most sensitive and W III isolates as the most resistant. Non-PPNG strains from Thailand were significantly more resistant than the other non-PPNG isolates of the same sero-group. There was, however, no significant difference in resistance between non-PPNG strains from Thailand and PPNG isolates of the same sero-group. PPNG strains of sero-group W I were significantly more sensitive than PPNG strains of sero-group W II, whereas there was no significant difference between PPNG isolates of sero-groups W II and W III. Non-PPNG strains, not from Thailand, of sero-groups W I and W II were significantly more susceptible to non beta-lactam antibiotics than PPNG strains of corresponding sero-groups, while no such difference could be demonstrated for non-PPNG and PPNG isolates of sero-group W III.