An approach to the mechanism of action of antibiotics is to ascertain metabolites which are involved directly in the inhibition of the bacterial cell by a specific antibiotic. A simple means of

A primary site of sparsomycin attack in Escherichia coli appears to be inhibition of synthesis of protein, which occurs at concentrations of sparsomycin that do not affect DNA or RNA synthesis. Sparsomycin interferes with the normal excretion of amino acids by E. coli. Some cross-resistance was observed between a culture resistant to sparsomycin and cultures resistant to other inhibitors of protein synthesis.

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Rifampicin is oxidized with hydrogen peroxide to a product that is fluorescent in alkaline solutions. Maximum fluorescence is measured at 480 nm with an excitation wavelength of 370 nm. The lower limit of detection of rifampicin in water is 0.1 μg/ml. A microbiological assay with Staphylococcus aureus 560 as the assay organism verified the reliability of the fluorometric assay. The fluorametric and microbiological assays were applied to the estimation of rifampicin in serum and were used to obtain concentration-time data for dogs that had been treated orally with 10 mg/kg rifampicin. Half-life of rifampicin in the dog was 8 h.

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