Resistance transfer factor in E. coli strains isolated from human and water sources

Conjugation experiments with a recipient E. coli strain F-lac-NaR were performed in order to determine the extent to which transferable drug resistance is prevalent among Gram-negative bacteria isolated from the following sources: healthy infants both treated and untreated with antibiotic drugs; healthy adults previously exposed to antibiotics; water sources; and nosocomial infections. Transferable drug resistance was demonstrated in 56.6% of E. coli isolates from the antibiotic-treated infant group, in 53.2% of isolates from untreated infants, and in 43% of isolates from the adult group. R factor was carried by only 8.3% of the strains isolated from water sources, and by 26.7% of the nosocomial strains. A positive correlation between transferable antibiotic drug resistance and resistance to mercury ions was found in donor and conjugate strains. Acridine and several of its derivatives were found to be active in preventing transfer of R factor.