Virulence of R-Factor-Bearing Salmonella typhimurium.
Antibiotic-resistant recombinants obtained from mating antibiotic-resistant Escherichia coli with virulent, antibiotic-sensitive Salmonella typhimurium are generally avirulent. After 32 consecutive transfers, two of four avirulent recombinants regained their virulence without loss of episome-mediated resistance.
Thiele
E H
EH
Merck Institute for Therapeutic Research, Rahway, New Jersey 07065.