Biomedical subjects

O Reichart

Publications and source records attributed to O Reichart.

7 recordsLinked to original sources

PubMed2007

Redox potential measurement as a rapid method for microbiological testing and its validation for coliform determination.

The redox potential is one of the most complex indicators of the physiological state of microbial cultures and its measurement could be a useful tool for the qualitative and quantitative determination of the microbial contamination. During the bacterial growth, the redox potential of the medium decreases. The shape of the redox potential curve is characteristic on the type of microorganism, and the rate of the change (dE/dt) is proportional to the living cell concentration. Defining the time required to reach a significant change in redox potential as Time to Detection (TTD), similarly to the impedimetric measurements, a strict linear correlation could be established between the TTD and the logarithm of the initial concentration of microorganisms. On the base of this calibration curve, the determination of living cell concentration could be simplified. For the experiments, a computer-controlled multi-channel measuring system and software was developed by the authors. The redox potential measurement method was tested and validated for the determination of coliform bacteria. The results have proved the high efficiency and reliability of the new method.

Area Under Curve↗

PubMed2006

The occurrence of Campylobacter species in Hungarian broiler chickens from farm to slaughter.

The reported number of human enteric diseases caused by thermotolerant campylobacters increased in the last few decades worldwide. The microorganism gets into the food chain mostly with poultry meat or meat products. We are not aware of the way the campylobacters infect the broiler flocks, and there is little information about the real prevalence, about the reaction of thermotolerant campylobacters to the environmental factors and about the possibilities of elimination of the bacteria from the food chain. As a part of the long study, samples were collected from a broiler flock from the first day of life to the slaughter of the animals, in summer and in winter. In the summer period, at the first two sampling days (days 0 and 12) all of the samples were negative. At day 26, one cloaca sample, one sample from the surface of the wall near the ventilation aperture and an insect-sample were positive. At day 42, we found Campylobacter spp. on every sampling point at the slaughterhouse. In the winter period, we could not find Campylobacter spp. either from 0 day old, or from 10- and 31-day-old chickens, but we found them at 42 days of age on the slaughter plant. At the slaughtering place, 93.3% of the live birds were infected with Campylobacter spp., and at the end of the processing line, the infection rate was 100%. We could isolate campylobacters from the hands of the workers and from the processing environment as well. Out of the positive samples, 95.5% was contaminated with Campylobacter jejuni.

Abattoirs↗

PubMed2001

Reaction kinetic interpretation of heat destruction influenced by environmental factors.

Based on reaction kinetics and thermodynamic considerations a mathematical model was developed to describe the thermal death rate of microbes as a function of environmental factors such as temperature, water activity, pH and redox potential. The mathematical model is discussed and validated by fitting to data sets of heat destruction of Lactobacillus brevis and Lactobacillus plantarum. The mathematical analysis of the kinetic model and the parameters of the model fitting demonstrate its applicability both for the prediction of the heat destruction rate and estimation of the thermodynamic parameters of heat destruction.

Hot Temperature↗

PubMed1998

A novel, selective synthetic acetamide containing culture medium for isolating Pseudomonas aeruginosa from milk.

A selective synthetic medium has been developed both in liquid (Z-broth) and solid (Z-agar) forms for selective isolation of Pseudomonas aeruginosa from foods. The simple, easy to prepare peptone-free synthetic medium contained acetamide that is metabolized to ammonia and acetic acid providing nitrogen and carbon supply. The medium contained no inhibitors. Selectivity of the liquid medium was tested by inoculation of pure cultures of different bacteria belonging to the groups Bacillus, Pseudomonas, Enterobacteriaceae and Staphylococcus. It was found that the selectivity of the medium was complete for the examined range of bacteria. However, a similar result was obtained when nitrofurantoin broth was used. Applicability of the synthetic agar medium was also tested by a nation-wide inter-laboratory test using two milk samples containing 10(3)/ml (sample I) and 10(5)/ml (sample II) Pseudomonas aeruginosa. According to this test, no microbiologically relevant differences were found between the results obtained by Z-agar and cetrimide-agar a frequently used selective agar in case of sample II. However, a relevant and statistically significant difference was found in the results of sample I in favour of the Z-agar, that could indicate the presence of a low number of bacteria. Concerning repeatability and reproducibility, Z-agar proved to be superior to cetrimide agar.

Acetamides↗

PubMed1994

Mathematical modelling of the combined effect of water activity, pH and redox potential on the heat destruction.

Heat destruction of seven foodborne microorganisms (Lactobacillus plantarum, Lactobacillus brevis, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Yarrowia lipolytica, Paecilomyces varioti and Neosartoria fischeri) as a function of the temperature, pH, redox potential and water activity was studied in synthetic heating media. Several mathematical models were developed for describing the heat destruction rate, most of them resulted in a good correlation between the fitted and measured values. The determination coefficients of the model-fitting were the best in case of lactobacilli and moulds (0.96-0.99) and the worst in case of the yeasts (0.81-0.88).

Food Microbiology↗

PubMed1994

Modelling the destruction of Escherichia coli on the base of reaction kinetics.

Assuming that the inactivation of microorganisms is due to a chemical reaction between a 'critical structure' of the cell and another reactant molecule, mathematical models of the reaction rates can be applied to the process. Considering the stoichiometric equation of the chemical reaction, the thermal death or disinfection of microbes can be described by an extension of the Eyring's model. The extended model is applicable not only to heat inactivation, but also to disinfection kinetics and to the effect of pH. Taking into account the effect of the water activity on heat destruction, the extended model has been modified empirically and fitted to experimental data on the heat destruction of Escherichia coli.

Disinfection↗

PubMed1991

Some remarks on the bias of the MPN method.

The estimation of cell number by using the MPN method was studied mathematically for three parallel inoculations from three decimal dilutions. As a result of computation it can be established that these estimations at a range of microbial numbers over 10 are biased. Confidential estimation could be obtained at cell numbers between 0 and 10 accepting only a few combinations of positive and negative test tubes. These are 1 0 0, 2 0 0, 3 0 0, 3 1 0 and 3 2 0.

Bias↗