Nature 234, 220 - 221 (26 November 1971); doi:10.1038/234220b0

fi^- R Factors giving Chloramphenicol Resistance

R. W. HEDGES & NAOMI DATTA

Department of Bacteriology, Royal Postgraduate Medical School, DuCane Road, London W12

ALTHOUGH many fi ⁺ R factors confer resistance to chloramphenicol, fi ^- R factors seldom do. Watanabe et al. ¹ stated in 1964 that all the naturally occurring fi ^- R factors which they had studied lacked chloramphenicol resistance. In our laboratory, no fi ^- R factor giving chloramphenicol resistance has been observed among several hundred drug-resistant strains of enteric bacteria. In 1968 Watanabe, Furuse and Sakaizumi² reported an fi ^- R factor (S−a) from Shigella which conferred chloramphenicol resistance at about the same level as fi ⁺ R factors. Aoki, Egusa, Ogata and Watanabe³ this year described R factors from the fish pathogen Aeromonas liquefaciens, which were all fi ^- and some of which carried chloramphenicol resistance determinants.

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