Testing sensitivity of Neisseria gonorrhoeae to spectinomycin

A concentration of 16 mg/l spectinomycin incorporated in agar gave the best discrimination between Neisseria gonorrhoeae sensitive and resistant to spectinomycin. This method was compared with spectinomycin sensitivity testing with 25 micrograms or 100 micrograms discs. Both methods agreed fully for 197 spectinomycin sensitive and three spectinomycin resistant gonococci. The agar incorporation "breakpoint" concentration technique failed to detect a small spectinomycin resistant population in a fourth isolate, which was detected by disc testing. It may be possible to predict the emergence of spectinomycin resistance among strains of N gonorrhoeae.