Development of resistance of gonococci to penicillin: an eight-year study.

During the last eight years, 5700 strains of Neisseria gonorrhoeae have been isolated and tested for sensitivity to penicillin and sulfadiazine in the Public Health Laboratory (Toronto). At the beginning of the study 63% of the strains tested were sensitive to a concentration of 0.01 unit of penicillin per ml. of diluent. Since then the gonococcus has gradually developed resistance to this antibiotic until 27% of the strains isolated are now resistant to a concentration of 0.3 unit/ml., and 8% are resistant to 1.0 unit/ml. To overcome this degree of resistance it is necessary to give a soluble penicillin preparation intramuscularly in very high dosage (2-8 million units). At the present time there is an urgent need for a satisfactory substitute for penicillin in the treatment of gonorrhea. None has yet been found.