In vitro susceptibility of Neisseria gonorrhoeae to spectinomycin examined by a broth dilution method.

The in vitro susceptibility of 113 strains of Neisseria gonorrhoeae to spectinomycin was determined by the broth dilution method and was compared with their susceptibility to penicillin and ampicillin. All strains demonstrated a susceptibility to spectinomycin in a range between 2.5 and 20 mug/ml; 96% of these strains were susceptible in a range from 5 to 10 mug/ml. The same strains were susceptible to ampicillin at concentrations between 0.06 and 0.5 mug/ml and to penicillin between 0.02 and 1.25 units/ml. For the majority of strains, the minimal inhibitory and bactercidal concentrations were identical; however, with more than 10% of the strains, the minimal inhibitory concentration was lower than the minimal bactericidal concentration.