Microcalorimetría: un método de diagnóstico precoz de infecciones bacterianas

Abstract

Microcalorimetry is a highly sensitive experimental technique that determines heat changes in any process or transformation. All organisms produce heat due to their metabolism. Rate of heat flow is an adequate measure of metabolic activity of living beings and their component parts. Microorganisms produce small amounts of heat: 1-3 pW per cell. Although the heat produced by bacteria is very small, their exponential reproduction in a culture medium permits heat detection through microcalorimetry. A thermal conductivity calorimeter of the Calvet type was used. The inside of the calorimeter contains two stainless steel cells (experimental and reference) with a screw on Teflon cap with a hole in the centre. Experiments were carried out with final concentrations of the order of 10 , 10 , 10 and 10 UFC/ml. These were kept at a constant temperature of 309.65 K. The plot of change in heat voltage vs. time enables us to obtain the characteristic growth curve for each bacterial strain. Thermograms were analyzed mathematically allowing us to calculate the constant growth, generation time and the amount of heat exchanged over the culture time