A transmissible plasmid determining lactose fermentation and multiple antibiotic resistance in a strain of Klebsiella pneumoniae.

In a wild strain of Klebsiella pneumoniae the plasmid that determined lactose fermentation also determined resistance to chloramphenicol, ampicillin, tetracyclines, streptomycin, spectinomycin, and sulphonamides. The plasmid transferred at a very low rate to Escherichia coli K12 and Salmonella typhi. By implanting other transfer factors in the strain the rate of transfer and the recipient range were increased. Plasmid transfer from the modified strain to Salm. typhimurium and Salm. gallinarum was detected in the alimentary tract of experimentally infected chicks fed diets containing ampicillin.