Characterization of medical relevant anaerobic microorganisms by isothermal microcalorimetry

Screening of Antimicrobial Properties and Bioactive Compounds of Pleurotus Ostreatus Extracts against Staphylococcus Aureus, Escherichia coli, and Neisseria Gonorrhoeae

In recent years, the potential of pathogenic bacteria to acquire resistance to a variety of antimicrobial drugs has developed significantly due to the indiscriminate exposure of a number of antibiotic compounds. The purpose of this study is to determine the antibacterial capabilities and activities of crude Pleurotus ostreatus extracts against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Neisseria gonorrhoeae (ATCC 49926), and nine multidrug-resistant clinical isolates of Neisseria gonorrhoeae. All of these isolates exhibited sensitivity to azithromycin and ceftriaxone, while the majority of antibiotic resistance was seen against penicillin G, sulphonamide, and ciprofloxacin. Fifty percent of the isolates exhibited absolute resistance to both sulphonamide and ciprofloxacin, whereas 40% of the isolates displayed absolute resistance to penicillin G. The antibacterial activity of P. ostreatus extracts examined in this investigation varied within the same species of microorganisms. Extract B and D, extracted in the presence of 20% wheat bran bagasse and 20% maize flour bagasse, respectively, had exceptional antibacterial activity against all target isolates examined. We observed the lowest concentration of antibacterial agent required to inhibit the target bacteria to be between 1 × 10^-3 mg/ml and 1 × 10^-6 mg/ml with an estimated probability of 0.30769, a lower 95% confidence interval (CI) of 0.126807, an upper 95% CI of 0.576307, an estimated probability of 0.15385, a lower 95% CI of 0.043258, and an upper 95% CI, respectively. The MBC of 1 × 10^-3 mg/ml was seen to eliminate 31% of the target bacteria. This dose was the most inhibitive. The antibacterial activity of all the extracts examined in the current study exhibited some degree of efficacy against both clinical isolates and standard strains. However, the majority of clinically isolated bacteria exhibited greater resistance to the extracts.

A standardized method for genus Colletotrichum characterization by isothermal microcalorimetry using thermokinetic parameters

A new standardized method, using isothermal microcalorimetry (IMC), was established to determine thermokinetic parameters from heat flow curves and to demonstrate the reproducibility and repeatability of the parameters of five Colletotrichum species on different days. Measurements on IMC were made at different periods and by two operators. Repeatability and reproducibility (R&R) measurement system analysis was performed on the technique used to measure the heat flow of Colletotrichum strains. The results showed that the %GageR&R was found to be within the acceptable ranges of a measurement system. Also, the parameters obtained from the curves were subjected to a combination of Principal Component Analysis (PCA) and Clustering, the data showed that the total heat (H_t) and maximum growth rate (μ_max) are probably the most specific distinguishing characteristic of the strains evaluated in this study. This study demonstrates, for the first time, the usefulness of IMC in obtaining heat flow curves and thermokinetic parameters, providing repeatable and reproducible measurements over a period and under controlled conditions, for future identifications of phytopathogenic fungi.

Simple Growth–Metabolism Relations Are Revealed by Conserved Patterns of Heat Flow from Cultured Microorganisms

Quantitative analyses of cell replication address the connection between metabolism and growth. Various growth models approximate time-dependent cell numbers in culture media, but physiological implications of the parametrizations are vague. In contrast, isothermal microcalorimetry (IMC) measures with unprecedented sensitivity the heat (enthalpy) release via chemical turnover in metabolizing cells. Hence, the metabolic activity can be studied independently of modeling the time-dependence of cell numbers. Unexpectedly, IMC traces of various origins exhibit conserved patterns when expressed in the enthalpy domain rather than the time domain, as exemplified by cultures of Lactococcus lactis (prokaryote), Trypanosoma congolese (protozoan) and non-growing Brassica napus (plant) cells. The data comply extraordinarily well with a dynamic Langmuir adsorption reaction model of nutrient uptake and catalytic turnover generalized here to the non-constancy of catalytic capacity. Formal relations to Michaelis–Menten kinetics and common analytical growth models are briefly discussed. The proposed formalism reproduces the “life span” of cultured microorganisms from exponential growth to metabolic decline by a succession of distinct metabolic phases following remarkably simple nutrient–metabolism relations. The analysis enables the development of advanced enzyme network models of unbalanced growth and has fundamental consequences for the derivation of toxicity measures and the transferability of metabolic activity data between laboratories.