[Contribution of potentiometry in the presence of lipoic acid to the study and evaluation of the in vitro antibacterial effects of betalactams].

We used potentiometry to assess the reduction of lipoic acid by a culture of Escherichia coli incubated with a beta-lactam. Two significant chronometric parameters were determined: one evaluates the antibiotic's killing effect, while the other reflects the stimulative effect exerted by the drug on cell reductive activity. For different beta-lactams, we did a quantitative study of the relationship between the concentrations of the antibiotic and each of the two potentiometric parameters. On the basis of our results we classified the different beta-lactams according to the degree of their killing and stimulative effects. Our study shows that potentiometry can provide original quantitative information on the in vitro antibacterial effect of beta-lactams.