MicroDSC study of Staphylococcus epidermidis growth

Zaharia, Dragoş; Iancu, Cezar; Steriade, Alexandru Tudor; Muntean, Alexandru; Balint, Octavian; Popa, Vlad Tudor; Popa, Mircea Ioan; Bogdan, Miron Alexandru

doi:10.1186/1471-2180-10-322

Cited by 13 publications

(13 citation statements)

References 11 publications

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“…All thermograms were processed as previously described [7,16,17] with baseline and time correction, thus eliminating the initial thermal perturbations and adjusting all experiments to a zero time reference. The baseline was calculated and subsequently subtracted using either Calisto software v1.077 (AKTS) and/or Peakfit v4.12 (SYSTAT).…”

Section: Resultsmentioning

confidence: 99%

“…To this purpose we have studied samples kept in cold storage, proven to yield better microcalorimetric reproducibility when working with single channel calorimeters, as shown in our previous paper [7]. Moreover, the present research aims to illustrate the most relevant parameters that can be used for the systematic classification of the growth patterns.…”

Section: Introductionmentioning

confidence: 97%

“…In our previous contribution, we have proved that the thermal growth signal obtained via IMC is reproducible within certain experimental conditions (temperature, bacterial concentration, sample thermal history) [7]. …”

Section: Introductionmentioning

confidence: 99%

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Comparative analysis of Staphylococcus aureus and Escherichia coli microcalorimetric growth

et al. 2013

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BackgroundMicrocalorimetric bacterial growth studies have illustrated that thermograms differ significantly with both culture media and strain. The present contribution examines the possibility of discriminating between certain bacterial strains by microcalorimetry and the qualitative and quantitative contribution of the sample volume to the observed thermograms. Growth patterns of samples of Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were analyzed. Certain features of the thermograms that may serve to distinguish between these bacterial strains were identified.ResultsThe thermograms of the two bacterial strains with sample volumes ranging from 0.3 to 0.7 ml and same initial bacterial concentration were analyzed. Both strains exhibit a roughly 2-peak shape that differs by peak amplitude and position along the time scale. Seven parameters corresponding to the thermogram key points related to time and heat flow values were proposed and statistically analyzed. The most relevant parameters appear to be the time to reach a heat flow of 0.05 mW (1.67 ± 0.46 h in E. coli vs. 2.99 ± 0.53 h in S. aureus, p < 0.0001), the time to reach the first peak (3.84 ± 0.5 h vs. 5.17 ± 0.49 h, p < 0.0001) and the first peak value (0.19 ± 0.02 mW vs. 0.086 ± 0.012 mW, p < 0.0001). The statistical analysis on 4 parameters of volume-normalized heat flow thermograms showed that the time to reach a volume-normalized heat flow of 0.1 mW/ml (1.75 ± 0.37 h in E. coli vs. 2.87 ± 0.65 h in S. aureus, p < 0.005), the time to reach the first volume-normalized peak (3.78 ± 0.47 h vs. 5.12 ± 0.52 h, p < 0.0001) and the first volume-normalized peak value (0.35 ± 0.05 mW/ml vs. 0.181 ± 0.040 mW/ml, p < 0.0001) seem to be the most relevant. Peakfit® decomposition and analysis of the observed thermograms complements the statistical analysis via quantitative arguments, indicating that: (1) the first peak pertains to a faster, “dissolved oxygen” bacterial growth (where the dissolved oxygen in the initial suspension acts as a limiting factor); (2) the second peak indicates a slower “diffused oxygen” growth that involves transport of oxygen contained in the unfilled part of the microcalorimetric cell; (3) a strictly fermentative growth component may slightly contribute to the observed complex thermal signal.ConclusionThe investigated strains of Staphylococcus aureus and Escherichia coli display, under similar experimental conditions, distinct thermal growth patterns. The two strains can be easily differentiated using a selection of the proposed parameters. The presented Peakfit analysis of the complex thermal signal provides the necessary means for establishing the optimal growth conditions of various bacterial strains. These conditions are needed for the standardization of the isothermal microcalorimetry method in view of its further use in qualitative and quantitative estimation of bacterial growth.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Comparative analysis of Staphylococcus aureus and Escherichia coli microcalorimetric growth

et al. 2013

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“…Some authors rely on a simple and descriptive approach [52,53]. In this approach some easily accessible curve parameters are extracted from the power time curve without need for further calculation.…”

Section: Descriptive Predictive and Comparative Approachesmentioning

confidence: 99%

Microcalorimetric assays for measuring cell growth and metabolic activity: Methodology and applications

Braissant

Bachmann

Bonkat

2015

Methods

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“…In the medical field, this method is very interesting due to the fast-growing nature of microorganisms and the resultant amount of heat that is soon produced [4]. In the last few years, it has been used to study the rapid detection of bacterial growth under different conditions [6][7][8][9] or microbial contamination [10][11][12]. Also, it has been employed to determine inhibitory effects and/or the minimal inhibitory concentration for different antimicrobial substances [13][14][15][16] and antibiotics [17][18][19] in a few hours.…”

Section: Introductionmentioning

confidence: 99%

Microcalorimetric study of the growth of Enterococcus faecalis, Pseudomonas aeruginosa and their mixtures in an enriched culture medium

Vázquez

Rivero

Mato

et al. 2015

J Therm Anal Calorim

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Microcalorimetry is a highly sensitive experimental technique that allows to determine the energy released by any process or transformation. In the field of medicine, it is interesting for investigations of microbial processes. The interaction relationship between Enterococcus faecalis and Pseudomonas aeruginosa was researched using a Tian-Calvet calorimeter equipped with two stainless steel cells (reference and experimental). Three samples from both bacteria were prepared in the following proportions: 20 ? 80 % (0.2 mL E. faecalis ? 0.8 mL P. aeruginosa), 50 ? 50 % (0.5 mL E. faecalis ? 0.5 mL P. aeruginosa) and 80 ? 20 % (0.8 mL E. faecalis ? 0.2 mL P. aeruginosa). Experiments were carried out at a concentration of 10 3 CFU mL -1 and a constant temperature of 309.65 K. Recording the heat voltage difference versus time, the growth curves for E. faecalis, P. aeruginosa and their mixtures were obtained. The differences in shape of curves of single microorganisms and their mixtures were compared. Also, the thermokinetic parameters of single microorganisms and their mixtures (growth constant, generation time, detection time and amount of heat released) were calculated.

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MicroDSC study of Staphylococcus epidermidis growth

Cited by 13 publications

References 11 publications

Comparative analysis of Staphylococcus aureus and Escherichia coli microcalorimetric growth

Comparative analysis of Staphylococcus aureus and Escherichia coli microcalorimetric growth

Microcalorimetric assays for measuring cell growth and metabolic activity: Methodology and applications

Microcalorimetric study of the growth of Enterococcus faecalis, Pseudomonas aeruginosa and their mixtures in an enriched culture medium

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