Antibiotic Susceptibility in Relation to Serogroup and Auxotype of Neisseria gonorrhoeae Isolates from Gabon

We tested 75 β-lactamase-positive (penicillinase-producing Neisseria gonorrhoeae; PPNG) and 147 β-lactamase negative (non-PPNG) strains of N. gonorrhoeae obtained during a twoyear period in Franceville, a semirural community in southeastern Gabon, for susceptibility to antimicrobial agents, auxotype, and serotype. The most common auxotypes were the nonrequiring and proline-requiring strains. Of the non-PPNG strains tested, 37% belonged to serogroup WI, 48% to serogroup WII, and 15% could not be grouped with commercially available antisera. Except for four strains that belonged to serogroup WII, the PPNG strains were classified as serogroup WI or ungroupable. We determined the concentrations at which 90% of strains were inhibited (MIC⁹⁰) for spectinomycin (32 mg/liter for both PPNG and non-PPNG), kanamycin (32 mg/liter for both PPNG and non-PPNG), tetracycline (2 mg/liter for non-PPNG, 1 mg/liter for PPNG), cefotaxime (0.03 mg/liter for non-PPNG, 0.008 mg/liter for PPNG), and penicillin (1 mg/liter for non-PPNG, >32 mg/liter for PPNG). A MIC of ⩾2 mg of tetracycline/liter was noted for 17% of the strains. Strains belonging to serogroup WII were more resistant to tetracycline and cefotaxime than other strains. Prolinerequiring strains were less susceptible to tetracycline, cefotaxime, and spectinomycin than the nonrequiring strains. The decreased sensitivity to penicillin (non-PPNG strains) and tetracycline was determined by proline-requiring strains belonging to serogroup WII.