Resistance of Salmonella typhi to chloramphenicol. I. A preliminary report.

Resistance of Salmonella typhi to chloramphenicol has not been reported so far except in strains made resistant in the laboratory. While examining 52 smooth strains of S. typhi and three smooth strains of S. paratyphi A 10 strains of S. typhi were found to be resistant to 50 to 500 mug. chloramphenicol. Of these 10 strains, eight appeared to be tolerant of the antibiotic, but the remaining two strains appeared to produce a substance that antagonizes or destroys chloramphenicol.