Streptomycin, assay

Drugs can also Interfere with laboratory results by negating certain nonspecific oxidation and reduction reactions essential for the chemical assay. Penicillin, streptomycin and ascorbic acid are known to react with cupric Ion thus, false positive results for glucose may occur If a copper reduction method Is used. If the specific enzymatic glucose-oxidase method Is employed, ascorbic acid can cause a false negative result by preventing the oxidation of a specific chromogen In the reaction. 

D.L. Simpson and R.K. Kobos, Potentiometric microbiological assay of gentamicin, streptomycin, and neomycin with a carbon dioxide gas-sensing electrode. Anal. Chem. 55, 1974-1977 (1983). 

A large number of antibiotics, namely chlortetracycline, doxycyline, gentamicin, neomycin, streptomycin, tobramycin and the like may be assayed tubidimetrically with fairly good accuracy. 

Extractions traditionally have been performed using buffers (j ) the same used to obtain the maximum response in standard curves. Unfortunately this has been a major failing of the plate diffusion assay systems. It is rare that the pH can be adjusted to the optimum necessary for greatest response simply by blending a matrix with buffer. As much as a 30 to 40% loss of activity can occur by not adjusting the pH properly analysis for residues of the streptomycins and erythromycin, for example, can yield results 20% lower by having the pH of the analyte 0.2 units below 8.0 if the pH is 0.5 units below 8.0, the loss of potency approaches 50% (14-15). 

The primary application of the procedure is the determination of the presence or absence of 3-lactam 7) residues in milk and secondarily to measure the levels quantitatively. The receptor assay system has now been expanded to qualitatively detect residues of tetracycline, erythromycin, streptomycin, chloramphenicol, novobiocin, and sulfamethazine in milk, serum and urine (Table II) (30). 

Cell Culture. KB cells were maintained in a humidified atmosphere of 5% carbon dioxide - 95% air at 37°C in the presence of modified Eagle s medium containing calf serum (10%), penicillin (100 jug/ml) and streptomycin (100 units/ml). Cells were routinely subcultured with 0.25% trypsin and stocks were discarded after twenty passages. All drugs were administered with fresh media 24 hours after subculture in the following concentrations TPA, 1.6 uM RA, 1.6 juM butyric acid, 2mM. Drug treatments were for 20-24 hours. Cells were harvested for enzyme assays with phosphate-buffered saline containing 0.05% EDTA and stored at -20°C in 0.32 M sucrose. 

Although one of the first assays for mutagenicity was a forward mutation to streptomycin resistance in E. coli, forward-mutation assays in bacteria have not been used as extensively as reverse-mutation assays. A forward-mutation assay should detect a wider range of mutagens than the presumably more restrictive reverse-mutation assays, but, in practice, there is little evidence to support this expectation. 

The mixed lymphocyte reaction (MLR) test was performed in 96-well flat-bottomed microtiter plates. Selected experimental agents were prepared as 10 mM stock solution in DMSO and a 50-fold dilution of this was prepared in RPMI. Serial dilutions were prepared from this subsequent solution and 10 xl of the diluted stock was added to the well to give concentrations in the assay starting at 9.5 xm. In each well was placed 1.5 x 105 donor cells to give a final volume of 0.2 ml RPMI 1640 medium supplemented with 10% human serum, 2mM L-glutamine, and penicillin/streptomycin. Cells were incubated at 37°C in a humidified atmosphere containing 5% carbon dioxide for 120 hours. 3H-Thymidine (0.5 xCi) was added in the final 6 hours of incubation and cell radioactivity levels determined, which were indicative of T-cell proliferation. 

Waksman and Reilly have summarized the factors which have a bearing upon the choice of the method to be employed in measuring quantitatively the activity or potency of an antibiotic substance. They have cited literature references to the more commonly used methods. Loo and coworkers have described a suitable method for the quantitative determination of streptomycin by the filter paper disc, agar plate diffusion technique using Bacillus subtilis as the test organism. The procedure proved satisfactory in the assay of surface and submerged culture beers and of preparations obtained in isolation and purification... 

Assay medium, DCCM-1 (defined cell culture medium—Biological Industries) supplemented with glutamine, penicillin, streptomycin, 0.001% DEAE Dextran, TPCK-treated trypsin, and 0.5% indubiose agarose. 

Trihydrochloride, C H CljNjO. The physical characteristics approx those of streptomycin. The specific rotation in water is 91 under conditions which give 86.1 For streptomycin trihydrochloride. Hydroxystreptomycin trihy-drochloride. when assayed against Bocilius subtilis. was found to be equiv to 7S4 g of streptomycin base/mg. The corresponding value of streptomycin is 842 ug/mg. LDW s.c. in mice 865 mg/kg (Ambrose). 

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