4.14 – CYCLOSERINE*

Publisher Summary Cycloserine (4-amino-3-isoxazolidinone) is an antibiotic produced by Streptomyces orchidaceus, Streptomyces garyphalus, Streptomyces lavendulae, or Streptomyces roseochromogenus. Concentrated aqueous solutions, crystalline solids containing significant amounts of moisture, or crystalline solids exposed to humid atmosphere are not stable. Cycloserine is active against both gram-negative and gram-positive bacteria, including mycobacteria. The activity of cycloserine is antagonized by D-alanine. High concentrations are obtained in urine. Detectable levels are still excreted in the urine 72 h after a single oral dose of 250 mg. Development of bacterial resistance to cycloserine has been demonstrated to occur. Resistance in Escherichia coli K-12 has been shown to develop in three distinct steps. Staphylococcus aureus ATCC 6538P or E.coli NRRL 4348 can be used satisfactorily for the assay. E. coli gives sharper zones.