In Figure 1, the signal perturbation was cut off 3. Perturbation during iso – non-iso – iso thermal switches. Due to ramp heating, experiments performed on samples kept in cold storage are mostly affected by switches in thermal program.
In Figure 5, the thermal “”wake-up”" of the bacterial population is masked by the inherent microDSC signal perturbation at iso – non-iso – iso thermal switches. This feature, also observed in Figure 2, can explain some of the reproducibility problems 4. Rate of ramp heating. A slow heating rate favors early stage bacterial growth within the non-isothermal regime. In spite of this, signal perturbation at thermal switch is lower and is amenable to subsequent signal processing. Slow check details heating is particularly suitable for samples with low concentration, where early stages of bacterial growth are not thermally important. Higher rates of ramp heating produce larger perturbations at the thermal switch but lower overlap with signal generated by bacterial growth. These higher rates are suited for
samples of higher concentrations, which generate a sizable early thermal signal. To optimize the time required for experiments and minimize overlap, a careful balance between these experimental parameters is necessary. Figure 5 Low temperature thermal Nivolumab inactivity check. Thermal signal of a concentrated sample (T600 = 48%) submitted to the following thermal regime: (i) sample cell introduction at room temperature; (ii) cooling with 1 K/min to 4°C; (iii) 20 hours of isothermal maintaining at 4°C; (iv) ramp heating with 1 K/min to 37°C; (v) 20 hours of isothermal maintaining at 37°C.
One can notice the thermal inactivity at 4°C followed by the “”wake-up”" BCKDHB of the bacterial population on heating. Perturbations caused by thermal switches are clearly overlapping with the intrinsic thermal signal of the bacterial population. Discussion Microcalorimetry is quickly gaining recognition as a tool in microbiology. In this contribution we sought to investigate the reproducibility and variability of growth pattern measurements carried out on a reference strain of Staphylococcus epidermidis. So far, many of the applications of microcalorimetry in medical science and research are qualitative in nature. Trampuz et al [11] have described a microcalorimetric method for the screening of platelet products for contamination. Daniels et al [13] point out that qualitative detection of bacterial growth is almost three times faster using microcalorimetry in a comparison with another commercially available rapid detection method. In both studies, positive diagnosis of bacterial growth was defined as a 10 μW increase in heatflow above baseline. In our paper, we present the microDSC analysis of Staphylococcus epidermidis growth in TSB. Experiments on freshly prepared samples presented above mimic the above-mentioned isothermal microcalorimetric (IMC) experimental setups [7–13].