Abstract
There are some different opinions on the problem concerning the reduction of activity of antituberculous drugs added into the egg media. According to the “Handbook of Tuberculosis Laboratory Method” issued by Veterans Administration, the amount of streptomycin (SM) and viomycin (VM) customarily increased three times and 25% respectively of the required concentration to compensate for the loss of drug activity on inspissation in egg-containing media. And the “guide to the examination of tubercle bacilli” in Japan describes the increased concentration of antituberculous drugs in the drug sensitivity test, such as, two-fold for SM, ten fold for kanamycin (KM) and 1.25 fold for VM. The report on the worldwide research of drug sensitivity test techniques performed by I. U. A. T. committee revealed that a considerable number of laboratories in the world have taken this matter into consideration. On the other hand, a part of investigators deny this phenomenon.
In this paper, we attempt to c larify the reasonable concentrations of drugs which are added. into egg media for drug sensitivity test of tubercle bacilli.
Experiment I: Minimal inhibitory concentrations o f antituberculous drugs in both the serum liquid medium and the egg solid medium.
SM, VM, KM, CPM, CS, PAS, TB1, INH, TH and EB were tested under the serious control repeatedly, and the results are shown in Fig.1. In this figure, the length of each bar means the growth grade in each medium and strain (H37Rv-standard strain, Yamamoto-fresh isolated strain, BCG). Of these drugs, SM, VM, KM, CPM and TH show remarkable differences between the drug-activities in the serum liquid medium and the egg solid medium.
Experiment II: Activity of drugs in water extracts of drug-containing media.
The activity of drugs in the supernatants of centrifuged homoginates o f drug-containing media was measured by the vertical diffusion method. As shown in Fig.2, a∼j, each drug has the characteristic lines according to the media used. The similar results as in Experiment I were obtained in this experiment, and the grade of reduction of drugs in the egg medium is different depending on the concentration of drugs. The equations which show the correlation between the drug-concentration added into egg media and the activity expressed on media were led from these lines. These equations are considered to be very useful for a practical purpose in the drug sensitivity test.
