[The use of mycobacteria in the estimation of the concentration of antibiotics, antimycotics and antituberculotics (author's transl)].

The possibility of using the rapid resistance test to determine the levels of antibiotic, antimycotic and antituberculotic drugs is systematically investigated. As a rule the incubation time reduced to seven days for tubercel bacilli results in a lower inhibitor concentration (MIC) than with other microbiological methods used in tuberculosis diagnostics due to a lower inactivation of the drugs. The MIC of antibiotics and antituberculotics is found between 0.02 and 15 microgram/ml; for penicillin G and nystatin between 100 and 400 microgram/ml. Urine added to the medium influences the MIC. A dilution of urine 1 : 100 corresponds to the MIC-value found in a control sample with aqua dest. For examining the level of antibiotic drugs in blood a dilution of the blood of at least 1 : 60 is necessary. In this way the levels of rifampicin and isoniazid may be examined. Only 0.1--0.2 ml of capillary blood are needed. If probenecid is administered simultaneously to the patient the rifampicin level in blood is increased for 6 hours. But this effect is small and does not justify a change in the usual dosage of rifampicin.