RESUMO
Fourteen strains of Enterobacteria, clinically isolated, were found to have multiple antibiotic resistance and harbour transferable plasmids. Curing of antibiotic resistance using ethidium bromide generally took place at low frequency with 70% of the tested strains indicating higher stability of these plasmids. The influence of pH, temperature and inoculum size, on the curing rats was studied. The effect of pH on curing was variable. pH 6 was the best for E2 and E3 while pH6 or pH8.5 was the best for the salmonella strains. The effect of temperature was also variable while the decrease in inoculum size resulted in an increase of curing frequency. The reason for such variable effects of these factors was discussed and the results led to a clue as to the etiology of R-plasmids