Background Microcalorimetry is an experimental technique that allows us to determine, with great sensitivity, the energy released during any process or transformation.
Purpose To determinate the applications of microcalorimetry as a method of early identification of bacterial infections.
Materials and methods A Calvety-type microcalorimeter was used, which maintains a constant temperature of 37 degrees centigrade. Samples of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were prepared at different concentrations (106, 105, 103 and 10 CFU/ml). Digested Soy-casein liquid culture was used as the culture medium. 7 ml of culture medium was injected into the control cell together with 1 ml of physiological saline, and 7 ml of culture medium was injected into the test cell. Both cells were placed in the microcalorimeter and left to stabilise for approximately an hour and a half. After this time, 1 ml of the test concentration was injected into the test cell.
Results By plotting heat voltage difference versus time, we obtain the characteristic bacterial growth curves of S. aureus, E. coli and P. aeruginosa at different concentrations. Analysing the thermograms obtained, The authors assumed that each bacterium has its own growth profile that repeats at all the concentrations studied, so that The authors obtained a ‘thermal fingerprint’ that allow us to identify the bacteria within the first 24 h of culture. Moreover, The authors observe that the time until the signal starts is greater when the concentration decreases, but in any case in less than 10 h The authors can identify the presence of bacteria in the culture medium, even for less concentrated samples (10 CFU/ml).
Conclusions Microcalorimetry allows us to determine the presence of bacteria in the sample in less than 10 h. In addition, each species of bacterium has its own growth profile which allows it to be identified in the first 24 h of culture, allowing treatment to be started early and tailored to the sensitivities of the causative agent.
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