Penicillin and Tetracycline Susceptibility of Neisseria gonorrhoeae Strains isolated during 1966 to 1975

Although the decreased susceptibility of gonococci to penicillin and tetracycline is a worldwide problem in the treatment of gonorrhea, the gonococci in the West Pacific region are particulary notorious in their resistance. Using a plate dilution method, susceptibility of the gonococci isolated at this institution during 1970 to 1975 was tested to penicillin and tetracycline, which are the most widely used antibiotics for the treatment of gonorrhea. The data of this susceptibility, together with that of the strains isolated during 1966 to 1969 from prostitutes, were analyzed and herewith reported.

The range of minimum inhibitory concentration (MIC) of penicillin was 0.01 to 2.0U/ml. Among the 191strains, 87.9% required MIC of 1.0U/ml and over, and 29.3% required 1.0U/ ml and over. The range of MIC of tetracycline was from 0.125 to over 2µg/ml. Among the 120 strains, 60% required MIC of 1µg/ml and over. This in vitro evidence indicates wide prevalence of less susceptible strains which are difficult to cure with conventional doses of penicillin or with tetracycline. Comparison of the degree and the frequency of less susceptible strains by the year of isolation showed some variation, which may however have been induced by the difference of sources, rather than by the difference of time of isolation.