Susceptibility of Agar-Entrapped Escherichia coli Cultures to Cefotaxime as Assessed by the Potentiometric Measurement of Lipoic Acid Reduction

This paper was presented at the 9^th Mediterranean Congress of Chemotherapy, Milan, Italy, June 1994.

Summary

We used an original potentiometric procedure to monitor the metabolic activity of biofilm-like structures and to assess their susceptibility to betalactam antibiotics. The reduction of exogeneous α-lipoic acid to dihydrolipoic acid by planktonic and agar-entrapped bacteria, metabolizing glucose, was followed by potential-time measurements using gold versus reference electrodes. Immobilized cultures displayed a lower susceptibility to cefotaxime than their free counterparts. The redox potential-time courses showed that the gel matrix was more rapidly oxygen depleted than the free-cell culture medium. The depletion of both glucose and dissolved O₂ inside the gel induced a breakdown in the reducing activity of agar-entrapped organisms.

Key words:

• Biofilm
• cell immobilization
• lipoic acid
• potential-time technique

Notes

This paper was presented at the 9^th Mediterranean Congress of Chemotherapy, Milan, Italy, June 1994.