Susceptibility of agar-entrapped Escherichia coli cultures to cefotaxime as assessed by the potentiometric measurement of lipoic acid reduction.
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 alpha-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.
Tresse
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Laboratoire des Polymères, Biopolymères, Membranes, URA 500 du CNRS, Université de Rouen, Mont-Saint-Aignan, France.
Jouenne
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Junter
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GA
D000362:Agar; D018441:Biofilms; D002439:Cefotaxime / Q000494:pharmacology*; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D011199:Potentiometry / Q000379:methods; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000378:metabolism*
D003470:Culture Media; D008063:Thioctic Acid; C015144:dihydrolipoic acid; D000362:Agar; D002439:Cefotaxime