Simultaneous resistance to heavy metals and antibiotics in escherichia coli strains isolated from clinical samples

ABSTRACT

Heavy metal ions and their compounds are essential for bacterial growth at very low concentration; however most of them have toxic effects at high concentrations. For Escherichia coli, simultaneous resistance to several heavy metal ions and antibacterial agents is reported. The present study is conducted to measure simultaneous resistance of some E. coli isolates, in which their tellurite sensivity had been investigated before, to heavy metal ions and antibiotics. In this laboratory study, in order to test bacterial resistance, the experimental investigations of antibiotic disc diffusion [agar serial dilution] were used to test 22 E. coli strains resistancy [5 isolates, MIC range <10 micro g/ml], [6 isolates, Minimum Inhibitory Concentration [MIC] range 10-40 micro g/ml] and [11 isolates, MIC range >40 micro g/ml] to heavy metal ions [Ag, Hg, Cd] and antibacterial agents; [Amoxicillin, Tetracycline and Gentamicin], simultaneously. These strains were isolated from urinary tracts and feces floor of clinical samples. Data were analyzed using PROBIT method. For Ag, the MIC was similar for all the isolates, therefore no difference was observed between sensitivity to tellurite and Ag. MIC level for Cd was significantly higher in the isolates, which were highly resistant to tellurite [p=0.008]. In case of Hg the isolates which were highly resistant to tellurite had a higher MIC than that of other isolates and the difference was statistically significant [p=0.008]. There were no significant differences between simultaneous resistance to heavy metals and different antibacterial agents; [Amoxicillin, Tetracycline and Gentamicin]. In total, there were statistically significant relationship between resistance to the antibacterial agents [Am, Gm, Te] and resistance to heavy metal ions in the tested isolates