Chip Calorimetry for Fast and Reliable Evaluation of Bactericidal and Bacteriostatic Treatments of Biofilms

Abstract

Chip calorimetry is introduced as a new monitoring tool that provides real-time information about the physiological state of biofilms. Its potential for use for the study of the effects of antibiotics and other biocides was tested. Established Pseudomonas putida biofilms were exposed to substances known to cause toxicity by different mechanisms and to provoke different responses of defense and resistance. The effects of these compounds on heat production rates were monitored and compared with the effects of these compounds on the numbers of CFU and intracellular ATP contents. The real-time monitoring potential of chip calorimetry was successfully demonstrated by using as examples the fast-acting poisons formaldehyde and 2,4-dinitrophenol (DNP). A dosage of antibiotics initially increased the heat production rate. This was discussed as being the effect of energy-dependent resistance mechanisms (e.g., export and/or transformation of the antibiotic). The subsequent reduction in the heat production rate was attributed to the loss of activity and the death of the biofilm bacteria. The shapes of the death curves were in agreement with the assumed variation in the levels of exposure of cells within the multilayer biofilms. The new monitoring tool provides fast, quantitative, and mechanistic insights into the acute and chronic effects of a compound on biofilm activity while requiring only minute quantities of the biocide.

A chip-calorimetric approach to the analysis of Ag nanoparticle caused inhibition and inactivation of beads-grown bacterial biofilms

“…For a faster monitoring of the response of the biofilm to the exposure of AgNPs, we used a method applied in recent biofilm investigations (Buchholz et al, 2010;Lerchner et al, 2008a). Briefly, a bead-biofilm sample of 6 μL was magnetically fixed inside the measurement chamber.…”

Rapid Clinical Bacteriology and Its Future Impact

“…Its potential use for the study of the effects of antibiotics was tested using an established model. The real-time monitoring potential of chip calorimetry was successfully demonstrated: a dosage of antibiotics initially increased the heat production rate probably due to activity of energy-dependent resistance mechanisms [101]. The subsequent reduction in heat production was probably due to the loss of activity and the death of the biofilm bacteria.…”

Development and applications of chip calorimeters as novel biosensors

“…Thermopiles (thermocouples connected in series) are used as thermometers in most chip calorimeters. 9,12,14,21,23,25,27,28,31,33,36,42,43,[47][48][49][50][51][52][53][54] The thermocouple converts the temperature difference to electric voltage via thermoelectricity. As thermopiles can have very high sensitivity (∆T: ∼10 µK) and do not use electric power to measure temperature, they are ideal for calorimetric applications.…”