title: Resistance of Salmonella typhi to chloramphenicol: Part II The mechanism of resistance.
abstract: A study of the action of the culture filtrates of 10 strains of S. typhi resistant to chloramphenicol showed that two of the strains produced an extracellular substance which enabled a strain of S. typhi sensitive to chloramphenicol to grow in a mixture of the filtrate and the antibiotic. A study of the properties of this substance suggested that it was an enzyme.