Studies on Resistance Transfer Factors

Abstract

The presence of infective R factors in a high proportion of multiple resistant wild Entero-bacteriaceae from the fecal flora of patients is demonstrated. Fre-quencies of transfer exceeding 1 x 10-2/recipient cell were found in most crosses of non pathogenic X pathogenic Enterobacteriaceae studied, and vice versa. The stability of resistance of the donor strain, the type of the media and the antibiotics used for selection of the R + recipient affect the results of the resistance transfer. The patterns and levels of resistance conferred to some recipients by infection with different R factors reproduce the pattern and levels of resistance of each donor. The clinical importance of high recipient efficiency of Salmonella typhi strains is emphasized.