[Survival of Escherichia coli in human blood serum as a function of R-plasmid content]

Thirty four strains of Escherichia coli of the pathogenic and nonpathogenic serogroups were tested for their survival in normal human blood serum as dependent on the content of the R plasmids. It was shown that the capacity for the survival of the E. coli strains of different origin was widely distributed. The value of the survival associated with the content of the R plasmids was higher in the E. coli strains of the pathogenic serogroup by comparison to that in the ordinary cultures. The capacity for the survival of the E. coli strains in the serum was more frequently accompanied by the tetracycline resistance.