Can the clinical efficacy of different antibiotic dosage regimens in gonorrhoea be predicted from the gonocidal effect of the corresponding plasma levels profiles simulated in vitro?

Two different gonococcal strains with equal minimum inhibitory concentrations of ceftriaxone are exposed to continuously changing concentrations of this antibiotic simulating the ones found in man after the single intramuscular application of different doses (1,000, 250, 125, 50 and 25 mg). In general the bactericidal effect on both strains decreases more or less steadily with decreasing concentrations of ceftriaxone. One of the strains, however, shows a markedly dropped bactericidal effect as soon as the dosage is further reduced from 250 mg. These findings agree with previous experience from clinical dose-range finding studies. Thus the in vitro model presented here may be valuable for predicting both the optimum dosage and the clinical efficacy of new treatment protocols for gonorrhoea.