To analyze the microcalorimetric behaviour of Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae, and to test the prospective use of microcalorimetry in the early diagnosis of infections by enterobacteria. For our experiments we used cultures of E. coli, P. mirabilis and K. pneumoniae. For the experimental setup, we used a Calvet microcalorimeter with the constant temperature of 309 K inside. Using the measured difference of heat power generated by the cells over time, we obtained growth graphs of the three bacterial species grown at different densities. The generated curves have characteristic plot that repeats for each bacterial species at all the concentrations studied. We observed an inversely proportional relationship between inoculum size and the time until signal detection; the smaller inoculum, the longer time for the signal detection. In all conducted experiments, even with low number of bacteria (10 CFU/ml) as inoculum, we could identify bacterial growth in the sample within 8 hours. Microcalorimetry could be an efficient technique used for the early detection and identification of enterobacteria in a culture medium.
Keywords: Enterobacteria; diagnosis of microbial infection; microcalorimetry; thermogram.