From a soil sample collected in a mulched field near Caracas, Venezuela, Burkholder1 of Yale University isolated a new strain of Streptomyces. Agar streak cultures of this organism were found to inhibit adjacent inoculums of a wide variety of gram-positive and gram-negative micro-organisms, including: Bacillus subtilis, S. aureus, Brucella abortus, Escherichia coli, Klebsiella pneumoniae, Salmonella schottmuelleri and Shigella paradysenteriae. When the Burkholder Streptomyces was grown in shaken flasks of liquid mediums, filtrates proved to possess antibacterial activity in broth dilutions against the same micro-organisms. From these filtrates a crystalline product was isolated, which was named "chloromycetin."
This crystalline material inhibits the growth of a wide range of gram-positive and gram-negative bacteria when tested in dilutions as high as 0.35 microgram per cubic centimeter. This is a higher effective dilution than that of the earlier antibiotics. Of particular interest was his observation that chloromycetin when injected into chick embryos shows
CHLOROMYCETIN. JAMA. 1948;138(6):432–433. doi:10.1001/jama.1948.02900060036012
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