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Background: Urinary tract infections are commonly encountered and often treated with antibiotics. However, the inappropriate use of the latter has led to the appearance of resistant strains. In this context we investigate the use of calorimetry to rapidly determine if a phage cocktail can be used as alternative to antibiotics. Methods: We used a commercially available phage cocktail from an online pharmacy and tested it against a strain of Escherichia coli and a strain of Proteus mirabilis. We used isothermal microcalorimetry to follow the metabolic activity of the bacterial culture treated with the phage cocktail. Results: Isothermal microcalorimetry was able to follow the dynamic of the bacterial metabolic activity reduction by the phage cocktail. Both pathogens were strongly inhibited; however, some regrowth was observed for E. coli in urine. Conclusions: Isothermal microcalorimetry proved to be a valuable technique when investigating the efficacy of phage cocktails against uropathogens. We foresee that isothermal microcalorimetry could be used to obtain rapid phagograms. [ABSTRACT FROM AUTHOR]

Colla corii asini (CCA) is a widely used animal-derived traditional medicine and nutritional supplement in China that has a variety of bioactive effects, especially anti-anaemic effects. To date, the effective substances in CCA are still unclear, thus limiting the evaluation of the quality and consistency of CCA. In this study, a microcalorimetry-based bioassay method was established to assess the quality of CCA by investigating its effects on the growth and metabolism of Escherichia coli, and ten biothermodynamic parameters were employed to characterize the biothermal changes. A principal component analysis (PCA) of these parameters showed that CCA significantly promotes the heat production of E. coli compared to that in the control group, and CCA showed an obvious dose–effect relationship from 0.625 to 20 mg mL−1. Then, the effects of 12 batches of CCA from three different manufacturers were studied at a concentration of 5 mg mL−1, which had a good effect and showed good intraday and daytime reproducibility. The results revealed distinctive characteristics among different manufacturers and good consistency within the same manufacturer according to the scores of the first principal component. In summary, the method based on microcalorimetric has good prospects in the evaluation of the quality of CCA. [ABSTRACT FROM AUTHOR]

In this work, isothermal microcalorimetry (IMC) was used to study the behaviour of mixed cultures of Pseudomonas aeruginosa with Staphylococcus aureus and Escherichia coli . The species were firstly studied as pure culture at 10 6  CFU/mL densities in nutrient broth (NB). The species were then introduced into NB to give an equivalent inoculum of 10 6  CFU/mL of each. Additionally, the inoculum density of one species was maintained at 10 6  CFU/mL and the other varied between 10 3 –10 5 CFU/mL. The IMC power-time curves were characteristic for the species in the medium. The total heat output ( Q t ), amplitude of first peak ( P 1 ), time of registration of first peak ( t 1 ), final metabolic/maximum peak ( P fmax ) and time of registration of the final metabolic/maximum peak ( t fmax ) were calculated from the power-time data. A mixed culture of P. aeruginosa and S. aureus at equal densities exhibited metabolism synonymous to P. aeruginosa alone. When the density of P. aeruginosa was decreased, S. aureus gradually recovered showing power-time profiles that demonstrated this. Mixed cultures of P. aeruginosa and E. coli at equal densities showed power-time profiles representative of both species. [ABSTRACT FROM AUTHOR]

The toxicity of five polyaromatic hydrocarbons (PAHs) to metabolism of Escherichia coli ( E. coli ) was evaluated with key parameters, including growth constant (k) and inhibitory ratio ( I) from microcalorimetry analysis. The results showed that the toxicity followed pyrene > 9-phenanthrol > phenanthrene > 3-phenanthrenecarboxylic acid > naphthalene for the chemicals tested. Basing on physical and chemical parameters of these five PAHs, the quantitative structure–activity relationships (QASRs) equation was established by multiple linear regression analysis, indicating that narcosis, a non-specific and non-reactive toxic action, plays the predominant role in toxicity of these five PAHs to bacterial cells. This study illustrates that the toxicity of PAHs are determined by the number of the aromatic ring and the substituent groups, higher toxicity associated with the higher number of the aromatic rings. [ABSTRACT FROM AUTHOR]

Bone and implant-associated infections caused by microorganisms that grow in biofilms are difficult to treat because of persistence and recurrence of infection. Along with surgical debridement, the combination of systemic and local administration of antimicrobials represents the background for an efficient treatment strategy. Gentamicin is one of most used antibiotics for the local treatment of bone-related infections, alone or in combination, due to its bactericidal and broad-range activity. Gentamicin-loaded beads (GLBs), composed of calcium sulfate/hydroxyapatite, were assessed for their in vitro antimicrobial activity against planktonic and biofilm S. agalactiae , S. aureus , S. epidermidis , E. faecalis and E. coli , using standard methods and ultra-sensitive isothermal microcalorimetry. Gentamicin released from GLBs to clinically relevant concentrations (200–2500 μg/mL) within 1 h was able to kill planktonic S. agalactiae, S. epidermidis and E. coli at lower concentrations (MIC: ≤4 μg/mL). Moreover, 12 and 23 μg/mL of released gentamicin were able to prevent bacterial adhesion and suppress a 24 h-old biofilm of E. coli , respectively. Conversely, higher amounts of antibiotic, ranging from 171 to 1260 μg/mL, were needed to prevent and eradicate biofilms of gram-positive bacteria. Likewise, the emergence of resistance to GLBs in vitro and the bacterial attachment on the bone graft substitute, when the amount of gentamicin in the material is reduced, were also reported. This study provides further information regarding the in vitro anti-biofilm activity of the biphasic gentamicin-loaded bone graft substitute, suggesting the validity of this antibiotic-loaded material for the prophylaxis and treatment of bone and implant-associated infections. [ABSTRACT FROM AUTHOR]

For seeking novel antibacterial agents with high efficacy and low toxicity to deal with drug resistance, the effects of Salvia miltiorrhizae from various sources on Escherichia coli were evaluated by microcalorimetry coupled with chemometrics. Firstly, the heat-flow power-time curves of E. coli growth affected by different S. miltiorrhizae samples were recorded. Then, some crucial quantitative thermo-kinetic parameters including growth rate constant, heat-flow power and heat output, etc. were obtained from theses curves and were further investigated by some powerful chemometric techniques including similarity analysis, multivariate analysis of variance, hierarchical clustering analysis and principle component analysis. By analyzing the principle parameters, growth rate constant of the second exponential phase ( k ) and the heat-flow output powers of the second highest peak ( P ), together with the derived parameter inhibitory ratio ( I, %), it could be quickly concluded that the tested S. miltiorrhizae samples from different sources in China exhibited strong antibacterial effects on E. coli and the samples from Beijing city exhibited the strongest anti- E. coli effects, which might be used as novel and underlying antibacterial candidates for the resistance of E. coli to the existing drugs in practice. This study provides a useful tool and helpful idea to accurately and rapidly evaluate the antibacterial effects of some complex matrices, offering some references for exploring new antibacterial agents. [ABSTRACT FROM AUTHOR]

This paper describes a novel approach to the quality control of a Chinese herbal injection based on microcalorimetric determination of its effect on the biothermal active fingerprint (BTAF) of Escherichia coli (E. coli) growth. Yinzhihuang Injection (YZHI) was selected for this proof of concept study. Reference samples of YZHI were collected and compared with test (stressed) samples prepared under different stress conditions. The BTAF of E. coli growth was found to be affected by YZHI and the changes were analyzed on the basis of eleven biothermokinetic parameters. Similarity and multivariate statistical analysis were used to investigate the differences between reference and test samples and discriminant analysis was used to delineate the altered samples. Reference samples were found to have coincident BTAFs with similarity index >0.99. Stressed samples showed differences in the BTAF which increased in line with decreased quality. Discriminant formulae were developed based on a sensitivity parameter which could identify all altered samples. In conclusion, BTAF can be used to assess the quality of YZHI both qualitatively and quantitatively and has the potential to provide a sensitive method for quality control of Chinese herbal injections.

In a majority of environments, microbes live as interacting communities. Microbial communities are composed of a mix of microbes with often unknown functions. Polymicrobial diseases represent the clinical and pathological manifestations induced by the presence of multiple infectious agents. These diseases are difficult to diagnose and treat and usually are more severe than monomicrobial infections. The interaction relationship between Enterococcus faecalis and Escherichia coli was researched using a Calvet calorimeter. Three mixtures of both bacteria were prepared in the following proportions: 20 + 80 % (0.2 mL E. faecalis + 0.8 mL E. coli), 50 + 50 % (0.5 mL E. faecalis + 0.5 mL E. coli) and 80 + 20 % (0.8 mL E. faecalis + 0.2 mL E. coli). Experiments were carried out at concentration of 10 CFU mL and a constant temperature of 309.65 K. The differences in shape of graph of E. faecalis, E. coli and their mixtures were compared. Also, the thermokinetic parameters such as detection time ( t), growth constant ( k), generation time ( G) and the amount of heat released ( Q) were calculated. [ABSTRACT FROM AUTHOR]

The root of Wikstroemia indica has been widely used in China as folk medicine for the treatment for arthritis, whooping cough, cancer, and bacillosis. However, the constituents which have antibacterial activity were not clarified yet. In this study, the antibacterial effect of five extracts from W. indica on Escherichia coli was evaluated by microcalorimetry coupled with agar dilution method. The ethanol extract of W. indica was isolated with organic solvents of different polarities including petroleum (P.E.) extract, chloroform (CHCl) extract, ethyl acetate (EtOAc) extract, n-butylalcohol (nBuOH) extract, and residue extract. The metabolic profiles of E. coli growth at 37 °C were measured by microcalorimetry. According to the principal component analysis, k, k, and P were obtained from heat flow power-time (HFP-time) curve. The agar dilution method was performed to verify the results of thermodynamics. The results of microcalorimetric experiment indicated that EtOAc fraction demonstrated the strongest antibacterial activity with half-inhibitory concentration of 92.4 μg mL. Meanwhile, similar results were gained from the common method of agar diffusion, which suggested that EtOAc extract could be further developed as antibacterial bioactive fraction of W. indica. Altogether, microcalorimetry is a useful technique to provide sufficient quantitative information and evaluate the antimicrobial effect with its sensitive. [ABSTRACT FROM AUTHOR]

To evaluate the activity of meropenem–amikacin and meropenem–colistin combinations with checkerboard broth microdilution (CKBM) compared with isothermal microcalorimetry (ITMC) assays against a multi-centric collection of multi-drug-resistant Gram-negative clinical isolates; and to compare the fractional inhibitory concentration (FIC) index and time to results of CKBM and ITMC. A collection of 333 multi-drug-resistant Gram-negative clinical isolates showing reduced susceptibility to meropenem (121 Klebsiella pneumoniae, 14 Escherichia coli, 130 Pseudomonas aeruginosa and 68 Acinetobacter baumannii) isolated from different centres (Florence, Madrid, Rotterdam and Stockholm) was included in the study. The antimicrobial activity of meropenem–amikacin and meropenem–colistin combinations was evaluated with CKBM and ITMC. FIC index results were interpreted as synergistic/additive and indifferent for values ≤0.5/0.51, respectively. Whole-genome sequencing data of a subset of strains were used to evaluate their clonality. In total, 254 and 286 strains were tested with meropenem–colistin and meropenem–amikacin combinations with ITMC and CKBM, respectively. Synergistic/additive effects were observed for 46 strains (20 K. pneumoniae, four E. coli, 22 P. aeruginosa) and 20 strains (three K. pneumoniae, 11 P. aeruginosa and six A. baumannii) with meropenem–amikacin and meropenem–colistin combinations, respectively, with CKBM. ITMC showed good concordance with CKBM, with 89.5% and 92.2% of cases interpreted within the same FIC index category for meropenem–amikacin and meropenem–colistin combinations, respectively. Most of the synergistic/additive effects were detected within 6 h by ITMC. ITMC showed very good concordance with CKBM against a large collection of multi-drug-resistant Gram-negative clinical isolates, and could be implemented for the rapid evaluation of in-vitro activity of antimicrobial combinations. [ABSTRACT FROM AUTHOR]

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Fighting against multidrug-resistant bacteria requires reliable methods to evaluate the effect of antibacterial agents. As a universal, non-destructive, and highly sensitive tool, microcalorimetry has been used in many biological investigations to provide continuous real-time monitoring of the metabolic activity. This method, based on heat-flow output, was used to evaluate the influence of two flavonoid compounds (liquiritigenin and liquiritin) on Escherichia coli. Some crucial information, such as the thermogenic power-time curve and thermokinetic parameters of E. coli growth affected by the two compounds, was obtained and further studied by chemometric techniques including similarity analysis, multivariate analysis of variance, and principal component analysis. By comparing the values of two main parameters, k (growth rate constant of the second exponential phase) and Q (heat output of the first exponential growth phase) of E. coli based on the box and whisker plot, liquiritigenin and liquiritin could be differentiated according to their antibacterial effects; liquiritin with IC (half-inhibitory concentration) of 198.6 μg mL expressed a stronger antibacterial effect than liquiritigenin with IC of 337.8 μg mL. The glucoside group in liquiritin containing four additional free hydroxyls in the diphenylpropane skeleton was crucial for inducing the antibacterial effect. Liquiritin might be a promising candidate against E. coli. This study provides a valuable method for searching for novel antibacterial agents using microcalorimetry with chemometrics. [ABSTRACT FROM AUTHOR]

Fructose-1-phosphate (F1P) is the preferred effector of the catabolite repressor/activator (Cra) protein of the soil bacterium Pseudomonas putida but its ability to bind other metabolic intermediates in vivo is unclear. The Cra protein of this microorganism (Cra PP ) was submitted to mobility shift assays with target DNA sequences (the P fruB promoter) and candidate effectors fructose-1,6-bisphosphate (FBP), glucose 6-phosphate (G6P), and fructose-6-phosphate (F6P). 1 mM F1P was sufficient to release most of the Cra protein from its operators but more than 10 mM of FBP or G6P was required to free the same complex. However, isothermal titration microcalorimetry failed to expose any specific interaction between Cra PP and FBP or G6P. To solve this paradox, transcriptional activity of a P fruB -lacZ fusion was measured in wild-type and Δ fruB cells growing on substrates that change the intracellular concentrations of F1P and FBP. The data indicated that P fruB activity was stimulated by fructose but not by glucose or succinate. This suggested that Cra PP represses expression in vivo of the cognate fruBKA operon in a fashion dependent just on F1P, ruling out any other physiological effector. Molecular docking and dynamic simulations of the Cra-agonist interaction indicated that both metabolites can bind the repressor, but the breach in the relative affinity of Cra PP for F1P vs FBP is three orders of magnitude larger than the equivalent distance in the Escherichia coli protein. This assigns the Cra protein of P. putida the sole role of transducing the presence of fructose in the medium into a variety of direct and indirect physiological responses. [ABSTRACT FROM AUTHOR]

Recently studies indicate that the microcalorimetry is a suitable measurement for metabolic activities of organisms by recording the rate of heat outputs. In this work, we investigated the growth thermogenic curves of Escherichia coli (E. coli) affected by three kinds of Glycyrrhiza extracts by microcalorimetry. The power-time and exponential phase power-time curves of the E. coli growth at various concentrations of extracts were generated. The kinetic parameters such as the growth rate constants (C), maximum power outputs (Pm), peak times (Tm), and inhibition ratios were calculated and the relationships between Pm or Tm and C were established. Also, the clear correlations among the antimicrobial effects, Pm and C were obtained. The results revealed the Glycyrrhiza extracts had inhibitory activities towards E. coli while the Glycyrrhiza polysaccharides showed the most potent effects. [ABSTRACT FROM AUTHOR]

Microcalorimetry is a technique that determines the heat flow produced as a result of microbial activities. The heat variations resulting from chemical reactions, which take place during metabolism, can be used to monitor bacterial growth in a culture medium. However, there are very few studies using calorimetry to investigate the relationships between two bacteria. In this work, we studied the interaction between E. coli and P. mirabilis, two bacteria belonging to the family Enterobacteriaceae. We have prepared three samples, mixing both enterobacteria at a concentration of 10 CFU mL but in different proportions. Experimental equipment used was a Calvet microcalorimeter, where a constant temperature of 309.65 K was maintained. Then, we compared the shape of the heat flow-time curves of single microorganisms and their mixtures. Also, we calculated the thermokinetic parameters such as growth constant ( k), generation time ( G), detection time ( t) and the amount of heat released ( Q). The results obtained showed that when E. coli and P. mirabilis were put together in the culture medium, the growth profile of P. mirabilis seemed to dominate, even at low proportions in the sample. [ABSTRACT FROM AUTHOR]

Demethoxycurcumin (DMC) is one of the major constituents in Curcuma longa L., and it is safe at a large dose range. In this study, the antimicrobial activity of DMC on Escherichia coli, Staphylococcus aureus, and Shigella dysenteriae was investigated by microcalorimetry and modified broth microdilution. Minimal inhibitory concentration and 50 % inhibiting concentration were determined by modified broth microdilution, which was fast and economical. Thermokinetic parameters were extracted from the heat-output power curves delineated by microcalorimetry, which was accurate and dynamic, and the multiple parameters were analyzed by similarity analysis and principle component analysis. The results demonstrated that DMC presented good antimicrobial activity, and the sequence of activity was as follows: E. coli > S. aureus > S. dysenteriae. This study provides a useful methodology for the determination of antimicrobial activity of natural products. In addition, it provides the foundation for the exploitation of DMC as a potential antimicrobial prodrug. [ABSTRACT FROM AUTHOR]

As a widely used traditional Chinese medicine (TCM), Radix Aconiti Lateralis Preparata ( Fuzi) is not only efficacious but also poisonous. Its toxicity and processed products should be taken into account and effectively evaluated. In this study, a non-invasive and non-destructive microcalorimetric method was employed to evaluate and compare the toxicity of Fuzi and its three processed products including Yanfupian, Heifupian, and Danfupian on Escherichia coli ( E. coli). Some important metabolic information, such as the power-time curves and some quantitative thermokinetic parameters including growth rate constant k, heat output power P, inhibitory ratio I, and half inhibitory concentration IC, of E. coli growth affected by various concentrations of Fuzi and its processed products were obtained. Combined with chemometric techniques including multivariate analysis of variance and principal component analysis on this information, it could be seen that Fuzi and its processed products could be distinguished according to their toxic effects on E. coli. The IC values of 14.6 mg/mL for Fuzi, 59.2 mg/mL for Yanfupian, 118.3 mg/mL for Heifupian, and 182.7 mg/mL for Danfupian illustrated that the sequence of toxicity on E. coli was Fuzi > Yanfupian > Heifupian > Danfupian. This study provided a useful method and idea of the combination of microcalorimetry and chemometrics for studying the toxic effects of TCMs and other substances. [ABSTRACT FROM AUTHOR]

Background: Microcalorimetric 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. Results: The 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. Conclusion: The 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. [ABSTRACT FROM AUTHOR]

Antibacterial activities of novel organoarsenic compounds As(III)-containing Schiff bases on Escherichia coli (CCTCCAB91112) were investigated by microcalorimetry in this study. The experimental result showed that the arsenic(III)-containing Schiff bases at micromolar concentration exhibit strong inhibition on the E. coli. Specifically, the growth rate constant k decreased, and the generation time t and the inhibitory ratio I (percentage) increased with the increased dose of the arsenicals as inhibitors. All of the arsenicals display the feature of considerable lag phase inhibition on the cell growth. The compound 4-(4-bromobenzaliminyl)phenylarsenoxide makes the lag phase of E. coli cell growth cycles to reach 650 min at 5 μmol/L. The compounds with donating electron groups at aromatic ring B have lower IC to present higher antibacterial activity. The compound 4-(4-hydroxyl-3-methoxylbenzaliminyl)phenylarsenoxide has the lowest IC (1.82 μmol/L) to show the strongest antibacterial activity among them. [ABSTRACT FROM AUTHOR]

Purpose: Isothermal microcalorimetry (IMC) has recently been reported as a new method to rapidly detect urinary tract pathogens (UTP). However, further application of microcalorimetry in the clinical setting requires a standardized procedure. An important step toward such standardization is to use a reproducible growth medium. In this study, we investigated the potential of artificial urine in combination with microcalorimetry for detection of common UTP. Methods: A microcalorimeter equipped with 48 channels was used. Detection was accomplished, and growth was monitored for four bacterial strains in artificial urine at 37 °C by measuring metabolic heat flow (μW = μJ/s) as a function of time. The strains were Escherichia coli, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus aureus. Result: Bacterial growth was detected after 3-32 h with decreasing inoculums down to 1 CFU. The gram-negative strains grew and were detected faster than their gram-positive counterparts. The growth rates the different strains were 0.75 ± 0.11 for E. coli, 0.74 ± 0.10 for E. faecalis, 1.31 ± 0.04 for P. mirabilis, and 0.56 ± 0.20 for S. aureus. The shape of individual heat flow curves was characteristic for each species independent of its initial concentration. Conclusions: IMC allows rapid detection of UTP in artificial urine. Clearly, different heat flow patterns enable accurate pathogen differentiation. UTP detection after only 4 h is realistic. The rapid detection of UTP tested in standardized artificial urine proves the diagnostic potential of IMC and warrants further microcalorimetric studies in the clinical setting of urinary tract infections. [ABSTRACT FROM AUTHOR]

Abstract: The power–time curves of Escherichia coli growth at 37°C affected by different concentrations of ephedrine were recorded by microcalorimetry. By analyzing some quantitative parameters from these curves using correspondence analysis, the effect of ephedrine on E. coli could be easily evaluated by analyzing the two main parameters, growth rate constant k 2 and maximum heat-output power P 2 of the second peak in the power–time curves. The results showed that the strong antibacterial effect of ephedrine on E. coli was concentration-depended: ephedrine at low concentration had poor inhibitory effect, and at high concentration notably inhibited the growth of E. coli. 376.8μg/ml of ephedrine could cause 50% inhibition on E. coli. Ephedrine presented strong antibacterial effect on E. coli, which might be used as a potential novel antibacterial agent in practice. Microcalorimetric investigation of the effect of antibacterial agent on bacterial pathogens was promising in comparison to other methods. [Copyright &y& Elsevier]

A microcalorimetric technique was used to evaluate the influence of both Levofloxacin lactate in sodium chloride injection (drug A) and Levofloxacin hydrochloride in sodium chloride injection (drug B) on the metabolism of Escherichia coli. By means of an isothermal calorimeter and ampoule method at 37 °C, the power-time curves of E. coli growth were obtained under different conditions. The parameters such as the growth rate constant k, maximum power output P, time t corresponding to the maximum power output and inhibitory ratio I of these two drugs were obtained. The results reveal that the inhibitory abilities enhance with increasing concentrations of the two drugs. The critical growth concentration and the half-inhibitory concentration IC were 0.15 and 0.079 μg mL (for drug A), 0.13 and 0.061 μg mL (for drug B), respectively. These results show the drug A has slightly better inhibitory effect on E. coli than that of drug B. [ABSTRACT FROM AUTHOR]

The strong toxicity of pathogenic bacteria has resulted in high levels of morbidity and mortality in the general population. Developing effective antibacterial agents with high efficacy and long activity is in great demand. In this study, the microcalorimetric technique based on heat output of bacterial metabolism was applied to evaluate the effect of berberine on Escherichia coli, Bacillus subtilis, individually and in a mixture of both using a multi-channel microcalorimeter. The differences in shape of the power-time fingerprints and thermokinetic parameters of microorganism growth were compared. The results revealed that low concentration (20 μg/mL) of berberine began to inhibit the growth of E. coli and mixed microorganisms, while promoting the growth of B. subtilis; high concentration of berberine (over 100 μg/mL) inhibited B. subtilis. The endurance of E. coli to berberine was obviously lower than B. subtilis, and E. coli could decrease the endurance of B. subtilis to berberine. The sequence of half-inhibitory concentration (IC) of berberine was: B. subtilis (952.37 μg/mL) > mixed microorganisms (682.47 μg/mL) > E. coli (581.69 μg/mL). Berberine might be a good selection of antibacterial agent used in the future. The microcalorimetric method should be strongly suggested in screening novel antibacterial agents for fighting against pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Abstract: Quantum dots (QDs) have a great potential for applications in nanomedicine. However, a few studies showed that they also exhibited toxicity. We used Escherichia coli (E. coli) as the model to study the effect of CdTe QDs on the cell growth by microcalorimetric technique, optical density (OD600) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra. Three size aqueous-compatible CdTe QDs with maximum emission of 543nm (green-emitting QDs, GQDs), 579nm (yellow-emitting QDs, YQDs) and 647nm (red-emitting QDs, RQDs) were tested. The growth rate constants (k) and half-inhibiting concentration (IC50) were calculated from the microcalorimetric data. The results indicated that CdTe QDs exhibited a dose-dependent inhibitory effect on cell growth. The order of toxicity is GQDs>YQDs>RQDs. The smaller the particle size of QDs is, the more toxicity it is. ATR-FTIR spectra indicated that the outer membrane of the cell was changed or damaged by the QDs, which may induce QDs and harmful by-products to enter into the cells. These could be one of the reasons that CdTe QDs have cytotoxic effects on E. coli. [Copyright &y& Elsevier]

A challenging method for sterility test which was rapid and reliable had been established to assess the adaptability and robustness of the microbial under different conditions. There were material and energy metabolism or exchange with microbial on microcalorimetry, as a result this method can be served as one of the optimization of thermodynamics sterility test. Thermal power-time curves under various environmental conditions (including processing temperature, storage time, and drugs inhibition) were determined. Typical microbial growth thermal power-time curves were obtained. The curves were analyzed qualitatively and quantitatively by similarity values of bio-profiles and thermodynamics parameters, such as the exponential growth rate constant ( k), detection time ( T). The similarity showed that microbial growth curves of low processing temperature, short storage time (1 month), and Traditional Chinese Medicine injection (Shuanghuanglian, contained native compounds) inhibiting were match better with the normal than other circumstance. Thermodynamic parameters indicated that the microcalorimetric method could detect the positive bacteria within 18 h (less than 10 cfu), and more quickly identify the different states of the bacterium growth and metabolism than routine sterility. In conclusion, characterized by of the specific and strong two-dimensional information, microcalorimetry could supply thermograms as biological profiles to describe the microbial activity under different conditions, which were not only used as a rapid and reliable identification of microbial, but also as a method for sterility test of microcalorimetry optimization. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a novel approach to the quality control of a Chinese herbal injection based on microcalorimetric determination of its effect on the biothermal active fingerprint (BTAF) of Escherichia coli (E. coli) growth. Yinzhihuang Injection (YZHI) was selected for this proof of concept study. Reference samples of YZHI were collected and compared with test (stressed) samples prepared under different stress conditions. The BTAF of E. coli growth was found to be affected by YZHI and the changes were analyzed on the basis of eleven biothermokinetic parameters. Similarity and multivariate statistical analysis were used to investigate the differences between reference and test samples and discriminant analysis was used to delineate the altered samples. Reference samples were found to have coincident BTAFs with similarity index >0.99. Stressed samples showed differences in the BTAF which increased in line with decreased quality. Discriminant formulae were developed based on a sensitivity parameter which could identify all altered samples. In conclusion, BTAF can be used to assess the quality of YZHI both qualitatively and quantitatively and has the potential to provide a sensitive method for quality control of Chinese herbal injections. [Copyright &y& Elsevier]

A thermal dynamic model of nanoformulations entrapped in artesunate liposomes was established and biological thermodynamics was applied for investigation of the drug formulations. Effects of artesunate liposomes on the growth metabolism of Escherichia coli were studied by microcalorimetry. The results showed that (1) Comparison of artesunate and artesunate liposomes, the thermogenesis curves of E. coli were significant different in the metabolic process: lag phase (AB), log phase (BC), stationary phase (CD), and decline phase (DE); (2) Linear fit of the data of total metabolic heat of E. coli effected by different concentration artesunate (1-300 μg), the equation can be obtained as follows: Y = 364720.61−1075.25 x, R = 0.9985; Linear fit of the data of total metabolic heat of E. coli effected by different concentration artesunate liposomes (30-120 μg), the linear equation can be obtained as follows: Y = 54251.5765−35.71122 x, R = 0.98345; (3) The half inhibitory concentration I was 50.05 μg/mL, the relative sensitivity was obviously different; (4) Artesunate liposomes having better sustained release properties as compare to artesunate. [ABSTRACT FROM AUTHOR]

The rate of heat output is one of the suitable measurements of metabolic activity of the organism. In this article, microcalorimetry was first applied to study the effect of volatile oil of dry ginger (ginger oil) on Escherichia coli and Staphylococcus aureus growth. The power-time curves were plotted with a TAM air isothermal microcalorimeter. The parameters such as the growth rate constant μ, the peak-time T, inhibitory ratio I, and half-inhibitory concentration IC were calculated. From the data, the relationships between μ and the concentration of ginger oil c were established. The results revealed that the μ of E. coli and S. aureus both gradually declined with the increase of the c, there were linear relationships between μ and c, and ginger oil had stronger inhibitory effect on S. aureus than on E. coli. Results obtained from our study strongly suggest that microcalorimetry is an ideal method to investigate the effect of drug on microorganism. [ABSTRACT FROM AUTHOR]

In this paper, crude monkshood polysaccharide was isolated from Radix Aconiti Lateralis Preparata. The effects of crude monkshood polysaccharide on Escherichia coli and Staphylococcus aureus were investigated by microcalorimetry. The power-time curves of the bacterial growth at various concentrations ( c) of crude monkshood polysaccharide were plotted with a TAM air isothermal microcalorimeter at 37 °C. The growth rate constant (µ), inhibitory ratio ( I), peak-height ( P), and peak-time ( t) were calculated. From the data, the relationship between µ and c also was established. The growth rate constant µ decreased with the increasing concentrations of crude monkshood polysaccharide. Moreover, P reduced and t increased with increasing concentrations. The experimental results revealed that crude monkshood polysaccharide had inhibitory activity towards S. aureus and E. coli. Results obtained from our study strongly suggest that microcalorimetry is a fast, simple, and more sensitive technology that can be easily performed to study the effect of drugs on bacteria. [ABSTRACT FROM AUTHOR]

Context: Extraction techniques may alter the antibacterial activity of Coptidis Rhizoma (C. Rhizoma), which is regarded as characteristic of this herb. Objective: To explore the best extraction techniques of C. Rhizoma and the fraction(s) with the strongest antibacterial activity. Methods: Using microcalorimetry, the influence of different extraction fractions of C. Rhizoma obtained by decoction, reflux, and ultrasound techniques on Escherichia coli growth was investigated by analyzing the power--time curves and some thermokinetic parameters. Then the antibacterial activities of each fraction of C. Rhizoma were compared by analysis of variance (ANOVA). Meanwhile, the minimum inhibitory concentration (MIC) of the strongest antibacterial fraction was determined by 2-fold dilution method. Results and conclusion: The petroleum ether (PE), chloroform (CHCl3), ethyl acetate (EtOAc), and n-butyl alcohol ( n-BuOH) fraction, water extract, and the residue after extraction all inhibited the growth of E. coli. The potency of the inhibitory effects was as follows: n-BuOH fraction > EtOAc fraction > CHCl3 fraction > PE fraction > residue after extraction > water extract. The decoction technique was regarded as the optimum extraction technique. The n-BuOH fraction from the decoction technique was observed to have the strongest antibacterial fraction with half-inhibitory concentration IC50 of 1.68 mg/mL and MIC of 200 μμg/mL. [ABSTRACT FROM AUTHOR]

Abstract: The emergence and prevalence of resistance to antibacterial agents is a pressing threaten for human health. Screening for novel antibacterial agents targeting not only multiplying but also non-multiplying bacteria using appropriate approach is in great demand. In this study, the microcalorimetric method was used to measure the metabolic curves of E. coli growth affected by chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA). By analyzing the metabolic curves and thermo- kinetic/dynamic parameters, the antibacterial activities of CDCA and UDCA on multiplying and non-multiplying bacteria of Escherichia coli (E. coli) were evaluated. The results illustrated that, for the multiplying metabolism of E. coli, the two compounds controlled the anaerobic fermentative, with IC50(1) (half-inhibitory concentration) of 566.2μg/mL for CDCA and 573.6μg/mL for UDCA, respectively, but had no effective action on aerobic metabolism of the bacteria. The action of the two compounds on the non-multiplying metabolism was studied by taking the heat output of E. coli in the stationary phase as the additive guideline of the activity. The values of IC50(2) were 543.4 and 547.5μg/mL, and MSC50 (minimum stationary-cidal concentration 50) were 532.6 and 537.3μg/mL for CDCA and UDCA, respectively. So, CDCA had more powerful antibacterial activity on E. coli than UDCA either for multiplying bacteria or non-multiplying metabolism, and they both showed stronger activities on non-multiplying metabolism than on multiplying metabolism of the bacteria. The microcalorimetric method should be strongly suggested in screening novel antibacterial agents for fighting against multidrug-resistant bacteria. [ABSTRACT FROM AUTHOR]

Abstract: Copper complexes: [Cu(phen)(L-Ser)(H2O)Cl] (1), [Cu(phen)(Gly)(H2O)]Cl·3H2O (2), [Cu(phen)(L-Ala)(H2O)]Cl·H2O (3), [Cu(phen)(L-Phe)(H2O)]Cl·2.5H2O (4), Cu(phen)2Cl2·6H2O (5) (phen=1,10-phenanthroline) were synthesized and characterized. The structure of 1 was characterized by X-ray crystallography and showed in a triclinic system with space group P1, a =6.8953(15) Å, b =10.737(2) Å, c =11.894(3) Å, α =110.395(3)°, β =94.183(4)° and γ =100.540(3)°. The antibacterial activities on Escherichia coli (E. coli) of these five copper complexes and CuCl2 (6) were investigated by microcalorimetry. By analyzing the obtained metabolic thermogenic data and curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC50), and generation time (t G) were determined. All these copper complexes could stimulate the growth of the E. coli at their lower concentration. At their higher concentration they all showed antibacterial action. The inhibition on E. coli was 5>1≈2≈3≈4>6. And the antibacterial mechanism was discussed preliminarily. [ABSTRACT FROM AUTHOR]

Abstract: Catechin is a major monomer of Chinese Rhubarb. Chinese Rhubarb has been claimed to have a therapeutic value as a bacteriostatic drug. It is also known that total rhubarb anthraquinone mixture and its individual components such as emodin are the effective components. However, the catechins component in Chinese Rhubarb such as catechin has not been characterized. In the present study, the power–time curves of Escherichia coli growth were obtained and the action on them by addition of catechin in different concentrations in vitro were studied by microcalorimetry. The results suggest E. coli growth is inhibited by catechin in a dose-dependent manner starting from the concentration of 0.05 to 1.6mgmL−1. The correspondence analysis reveals k 2 and P 2 are the significant parameters to evaluate the anti-microbial effect. Microcalorimetry is a useful tool to evaluate the anti-microbial effect with its sensitive and significant quantitative information. [ABSTRACT FROM AUTHOR]

Abstract: A complex of lanthanum perchloric acid coordinated with glutamic acid, La(Glu)(Im)6(ClO4)3·4HClO4·4H2O was synthesized and characterized. The biological effect of the complex was evaluated by microcalorimetry on the growth of E. coli DH5α. Power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal Microcalorimeter at 37°C. From the power–time curves, the parameters such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P m) and the time of the maximum heat power (t m) were obtained. The results show that the concentrations of the complex affect obviously the growth metabolism of E. coli DH5α. The stimulatory effect on growth of E. coli DH5α was observed when the concentration of the complex was kept in the range of (0–0.5μgmL−1). In contrast to the lower concentration, in the case of higher concentration of the complex (0.5–5.0μgmL−1), an inhibitory effect occurred. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the toxicity of two isomeric alkylphthalates, i.e., di-n-octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) to two model bacteria, Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), which have been previously used to study the toxicity of environmental pollutants. Microcalorimetry was used as the key analytical tool alongside scanning electron microscopy (SEM) and traditional microbiology techniques. The thermokinetic parameters from microcalorimetry showed that the phthalates had a biphasic effect on the metabolic activities of the bacteria; serving as energy sources for the bacteria thereby stimulating their growth at low dosages (≤150μg/mL), but displaying inhibitory effects at higher dosages (≥300μg/mL), indicated by a sharp decrease in growth rate constants at 450μg/mL. The SEM revealed that the bacterial cells were morphological deformed, with shrunk cells and elongated strands at 600μg/mL of both phthalates. The elongated strands inferred that the phthalates inhibited the reproductive processes of the bacteria by possibly impeding some stages of cell division. The half inhibitory concentrations of the phthalates showed that DEHP was more toxic than DOP. Additionally, E. coli, a facultative anaerobe, was more susceptible to the toxic effects of phthalates than B. subtilis, an obligate aerobe capable of forming endospores crucial for tolerating extreme environmental conditions. [ABSTRACT FROM AUTHOR]

The action of Cornu Cervi Pantotrichum (CCP), Cornu Cervi (CC) and Cornu Saigae Tataricae (CST) on Escherichia coli growth were investigated using microcalorimetry to find the heat change regularity of microbial growth. The similarity of thermogenic curves and thermodynamics parameters were investigated as evaluation index, such as the growth rate constant in the first exponential phase (k1), maximum power in the first exponential phase (P1), maximum power in the secondary exponential phase (P2), peak time in the first exponential phase (T1), peak time in the stationary phase (T2) and the total heat production in stage 1 (Q1), and the total heat production in stage 2 (Q2). Chemometric analysis was used as a reference for the bioactivity evaluation of medicinal animal horns. The results indicated that the similarity between CST and the control was smaller than that between CCP, CC and the control. Both CCP and CC could increase the heat in the microbial growth, whereas CST decreased it. The biotic thermal activity of different medicinal animal horns was objectively, qualitatively, and quantitatively evaluated by the similarity of thermogenic curves and thermodynamics parameters analysis. [ABSTRACT FROM AUTHOR]

In this paper, the biological activation of heteropoly complex of molybdotungstosilicate containing lanthanum K10H3La(SiMo6W5O39)2⋅26H2O (LaW5) was investigated by spectroscopic approach and microcalorimetry under the human physiological conditions. Fluorescence spectroscopy in combination with UV–Vis absorption spectroscopy was employed to investigate the binding of LaW5 to bovine serum albumin (BSA). In the mechanism discussion, it was proved that the fluorescence quenching of BSA by LaW5 is a result of the formation of LaW5–BSA complex. Binding parameters were determined using the Stern–Volmer equation. The results of thermodynamic parameters ∆ G, ∆ H, ∆ S at different temperatures indicate that van der Waals interactions and hydrogen bonds play a major role for LaW5–BSA association. The distance r between donor (BSA) and acceptor (LaW5) was obtained according to fluorescence resonance energy transfer. Furthermore, the calorimetric method was used to monitor the biological activity of LaW5 in Escherichia coli. [ABSTRACT FROM AUTHOR]

Abstract: The fingerprints of Rhizoma coptidis from various sources were established by ultra performance liquid chromatography (UPLC) and the anti-bacterial activities of R. coptidis on Escherichia coli (E. coli) growth was studied by microcalarimetry. The UPLC fingerprints were evaluated using similarity analysis (SA) and hierarchical clustering analysis (HCA). Some quantitative parameters obtained from the thermo-genic curves of E. coli growth affected by R. coptidis were analyzed using principal component analysis (PCA). The spectrum–effect relationships between UPLC fingerprints and anti-bacterial activities were investigated using canonical correlation analysis (CCA). The results showed that close correlation existed between the spectrum–effect relationships. Berberine, jateorrhizine and palmatine in the UPLC fingerprints might be the main anti-bacterial components. The anti-bacterial activities of R. coptidis were related with the main active constituents, along with the production place and the harvesting time of this herb, the latitude and longitude of the place. This work provides a general model of the combination of UPLC and microcalorimetry to study the spectrum–effect relationships of R. coptidis, which can be used to discover principle components of it on bioactivity. [Copyright &y& Elsevier]

The inhibitory effects of three berberine alkaloids (BAs) from Coptis chinensis Franch on Bifidobacterium adolescentis growth were investigated by microcalorimetry. The growth rate constant ( k) and maximum heat-output power ( Pmax) decreased and peak time of maximum heat-output power ( tp) prolonged with the increase of BAs concentration. Half inhibitory ratios (IC50) BAs were respectively 790.3 (berberine), 339.6 (coptisine) and 229.8 μL−1 (palmatine), which indicated the sequence of their antimicrobial activity: berberinecoptisine>palmatine. The structure-function relationship of BAs indicated that the functional group methylenedioxy or methoxyl at C2 and C3 might be the major group inducing the activities of BAs on E. coli and B. adolescentis. Meanwhile, the substituent groups at C2, C3, C9 and C10 almost had equal effect on B. shigae. [ABSTRACT FROM AUTHOR]

Using TAM III multi-channel calorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd(II)) and hexavalent chromium (Cr(VI)) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant ( k), peak-heat output power ( Pmax) and the number of living microorganisms decreased with increasing concentration of Cd and Cr. The accumulation of Cr on E. coli was conducted by HPLC-ICP-MS. Cr6+ accumulation by Escherichia coli was increased steadily with increasing Cr6+ concentration. The results revealed that the change in some thermo-kinetic parameters could have good corresponding relationship with metal accumulation. Our work also suggests that microcalorimetry is a fast, simple, more sensitive, on-line and in vitro method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods, and can combine with other analytic methods to study the interaction mechanism between environmental toxicants and microbes. [ABSTRACT FROM AUTHOR]

The inhibitory effect of three berberine alkaloids (BAs) from Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Bifldobacterium adolescentis growth was investigated by microcalorimetry. The power-time curves of B. adolescentis with and without BAs were acquired, meanwhile the extent and duration of inhibitory effect on the metabolism were evaluated by the growth rate constant (k), half inhibitory ratio (IC[sub50]), maximum heat-output power (Pmax), peak time of maximum heat-output power (t[subp]) and total heat production (Q[subt]). k, P[subma]x and Q[subt] decreased, and t[subp] was prolonged with the increase of BAs concentration. The IC[sub50] of BAs is 806 μg/mL for berberine, 341 μg/mL for coptisine and 236 μg/mL for palmatine. The sequence of antimicrobial activity of BAs is berberine < coptisine < palmatine. Combined with previous studies, it could be shown that the sequences of antimicrobial activity of BAs on both Bacillus shigae and Escherichla coil are berberine > coptisine > palmatine. The structure-function relationship of BAs indicates that the functional group methylenedioxy or methoxyl at C2 and C3 might be the major group inducing the activities of BAs on E. coil and B. adolescentis. Meanwhile, the substituent groups at C2, C3, C9 and C10 almost have equal effect on B. shigae. [ABSTRACT FROM AUTHOR]

This paper shows a software system developed in Delphi for Windows for data acquisition using a multipurpose acquisition card Advantech PCL-711B connected to the Bioactivity Monitor LKB-2277. The data obtained from the acquisition is used for having the corresponding profiles using microcalorimetry of the different bacterial strains and their interrelation with the different culture media and their biological activity. The acquisition can be performed in four channels simultaneously. The acquisition time period, the time interval for saving the results, the selection of the channels, the top and the bottom limits for the graphic panel and the digital filtering of the signals can be programmed. It is also possible to show the curves of previous saved data. Using this software it was possible to obtain the calorimetric profiles of different pattern bacterial strains as Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. In the present work an LKB-2277 Bioactivity Monitor was used to determine the effect of PAMAM dendrimers (-NH2, -OH) G4 on thermogenic curves of the growth metabolism of Escherichia coli. [ABSTRACT FROM AUTHOR]

Microcalorimetry was applied to study the effect of cephalosporins (cefazolin sodium and cefonicid sodium) on the E. coli growth. The microbial activity was recorded as power-time curves through an ampoule method with a TAM Air Isothermal Microcalorimeter at 37°C. The parameters such as the growth rate constant ( k), inhibitory ratio ( I), the maximum power output ( P m) and the time corresponding to the maximum power output ( t m) were calculated. The change tendencies of k, with the increasing of concentration ( C) of the two cephalosporins, are similar which show that cefazolin sodium and cefonicid sodium have the same inhibitory mechanism. The experimental results reveal that cefonicid sodium has a stronger antibacterial activity towards E. coli than that of cefazolin sodium and this was coincide with the clinical manifestations. [ABSTRACT FROM AUTHOR]

Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II) (denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)3+) on ( E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output P m and the time ( t m) corresponding to the P m were obtained. The half-inhibitory concentrations (IC50) of Co(II) and Co(sep)3+ to E. coli DH5α were 15 and 42.1 mg mL−1, respectively. The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)3+. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)3+. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)3+ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the spectrum-effect relationships between HPLC fingerprints and the anti-bacterial activities of EtOAc extracts from Radix Isatidis. Fingerprints of EtOAc extracts of Radix Isatidis from various sources were established by a High-Performance Liquid Chromatography. The process of Escherichia coli (E. coli) growth affected by EtOAc extracts was monitored using a Thermal Activity Monitor (TAM) Air Isothermal Calorimeter by microcalorimetry. By analyzing the power–time curves, quantitative parameters, such as growth rate constant k, maximum heat-production rate P m, appearance time t and total heat-production Q were obtained to characterize the interactions of E. coli and the EtOAc extracts from Radix Isatidis. The HPLC fingerprints were investigated using hierarchical clustering analysis. The main thermo-kinetic parameters from the power–time curves were analyzed using principal component analysis. The spectrum-effect relationships between the HPLC fingerprints and anti-bacterial activities were analyzed with multivariant correlation analysis. Close correlation existed between the spectrum-effect relationships of the EtOAc extracts. Salicylic acid in the HPLC fingerprints might be one of the anti-bacterial components. This work provides a general model of the combination of HPLC and microcalorimetry to study the spectrum-effect relationships of EtOAc extracts from Radix Isatidis, which can be used to search for principal components of Radix Isatidis on bioactivity. [Copyright &y& Elsevier]

Abstract: The growth thermogenic curves of Escherichia coli (E. coli) affected by berberine, coptisine and palmatine were determined quantitatively by microcalorimetry. The power–time curves of E. coli with and without the three berberines alkaloids (BA) were acquired, meanwhile the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constant (k), half-inhibitory ratio (IC50), peak time of maximum heat-output power (t p), total heat-production (Q t) and so on. The inhibitory effects of BA on E. coli revealed that the sequence of their antimicrobial activity was berberine > coptisine > palmatine. The functional groups methylenedioxy at C2 and C3 on phenyl ring improve antimicrobial activity more remarkably than methoxyl at C2 and C3 on phenyl ring. However, the antimicrobial activity does not vary significantly with methylenedioxy or methoxyl at C9 and C10 on phenyl ring. [Copyright &y& Elsevier]

A microcalorimetric technique based on the metabolic heat production from cultured cells was used to investigate the effect of kanamycin on the growth and metabolism of recombinant Escherichia coli. Power-time curves of growing recombinant Escherichia coli cell suspensions treated with different kanamycin doses were recorded and were described very accurately by the generalized logistic equation. The rate constant (k) is kanamycin concentration-dependent and the relationship between k and C (kanamycin dose) is nearly linear. The 50% inhibitory concentration IC50 was 88.49 µg/mL. The experimental results revealed that high doses of kanamycin inhibited the growth of recombinant E. coli during the log phase and promoted growth during the stationary phase. These results are important for deciding the optimum kanamycin dose for the maximal synthesis of human-like collagen. [ABSTRACT FROM AUTHOR]

The biological activity of a kind of hetero-bimetallic Schiff-base complex was studied using Escherichia coli ( E. coli) cell as the target. By microcalorimetry, the difference of anti-bacterial activity between the binuclear Schiff-base and the ligand was determined and analyzed. To analyze the inhibition of the bacterial growth internally, the E. coli cells grown in the presence of hetero-bimetallic Schiff-base complex were observed by scanning electron microscopy. The images in high resolution revealed the damage of outer cell membrane caused the inhibitory effect on E. coli. Inductively coupled plasma-mass spectrometry results proved the absorption of the complex by cells, which confirmed the interaction between the Schiff-base and biological macromolecule. [ABSTRACT FROM AUTHOR]

The isoquinoline alkaloids were isolated from traditional Chinese drugs of Phellodendri Cortex, Radix Stephaniae Tetrandrae, Corydalis Yanhusuo and Corydalis Bungeana. The power-time curves of growth of E. coli at different concentrations of isoquinoline alkaloid at 37°C were determined by a 2277 Thermal Activity Monitor. The rate constant of bacteriostastic activity was calculated. The relationship between growth rate constant and concentration was established. The optimum bacteriostastic concentration was determined. Experimental results have indicated that all the isoquinoline alkaloids isolated from the four kinds of traditional Chinese drugs have bacteriostastic activity and the order is Phellodendri Cortex>Radix Stephaniae Tetrandrae>Corydalis Yanhusuo>Corydalis Bungeana. [ABSTRACT FROM AUTHOR]

The thermogenic curves of metabolism of the four strains of Escherichia coli pUC19cab/JM109, pUC19cab/XL-IBlue, JM109 and XL-IBlue were determined using the LKB-2277 BioActivity Monitor and the ampoule method at 37°C. The pUC19cab/JM109 and pUC19cab/XL-IBlue are recombinant E. coli strains bearing the same foreign plasmid pUC19cab, which confers the ability to produce polyhydroxyalkanoates (PHAs). The yield of PHAs of pUC19cab/XL-IBlue was higher than that of pUC19cab/JM109. XL-IBlue and JM109 were the host bacteria. The heat flow of these strains was XL-Blue≈JM109>pUC19cab/JM109>pUC19cab/XL-IBlue. These results indicate an obvious interrelation between the PHAs production and the heat flow rate of E. coli strains. [ABSTRACT FROM AUTHOR]