Classification of wild and antibiotic resistant bacteria with electrode

Cyclic voltammograms of wild and antibiotic resistant cells were obtained by an electrode system with a basal plane pyrolytic graphite and a membrane filter to trap bacteria after the cells were incubated at 37°C for 1 h in the medium containing 50 μg/ml ampicillin or 20 μg/ml tetracycline. Wild and ampicillin or tetracycline resistant strains of E. colt were classified from the peak potential and shape of the cyclic voltammograms, when the potential of the graphite electrode was swept in the range from 0 to 1.0 V versus saturated calomel electrode (SCE). The peak current of wild strains decreased with increasing antibiotic concentration. On the other hand, the peak current of antibiotic resistant strains slightly decreased for ampicillin and almost constant for tetracycline. The peak current increased with increasing initial cell numbers. Consequently it was shown that cell number and minimal inhibitory concentration were estimated from the peak current of the cyclic voltammograms. Electrochemical reaction of CoA in the cell contributed to the classification of the wild and antibiotic resistant strains of E. coli. The minimal inhibitory concentrations obtained by the electrode system were almost in good agreement with those obtained by the conventional method.