High pressure inactivation of Enterococcus faecium - modelling and verification

Abstract

Landfeld A., Strohalm J., Kýhos K., Průchová J., Houška M., Novotná P., Schlemmerová L., Šmuhařová H., Špelina V., Čermák P., Pavlišová K., Měřička P. High-pressure inactivation data were obtained for model working suspensions of Enterococcus faecium in saline solutions in pH range from 5.5 to 6.8, at water activity 0.99 (corresponding to the saline solution). The data were predicted for the pressure range of 450 MPa to 550 MPa, at the initial model suspension temperature 6-7°C prior to pressurising. The results indicate that E. faecium is a highly resistant organism under physiological pH values. With decreasing the substrate pH, the tolerance to the inactivation effects of high pressure decreased. The high-pressure inactivation proved ineffective for the above organism in the range of physiological pH values. The values for high-pressure inactivation model were specified and the calculated parameters of high-pressure inactivation were compared to the experimental data for the working suspensions of E. faecium in cow and human milks. As to cow milk, the predicted data showed some deviation from the model experimental results, while with human milk the model failed completely. High-pressure inactivation of E. faecium in human milk proved to be significantly more effective than that predicted by a model based on the saline solution.

Bacillus cereus as a Major Cause of Discarded Pasteurized Human Banked Milk: A Single Human Milk Bank Experience

“…Better diagnostics has led to an enlargement of the spectrum of microbes capable of surviving pasteurization (Figure 7, Table 5). In addition to the pathogenic or potentially pathogenic genera identified in our previous studies [25,33], Burkholderia, Kocuria, Moraxella, Roseomonas, Sphingomonas and Stenotrophomonas were identified in this study (Figure 7, Table 5). We encountered similar genera described by others who used the MALDI method [31], e.g., Moraxella spp., Stenotrophomonas spp., and Acinetobacter spp.…”

“…Changing technology to the innovative pasteurization procedures recently described [ 20 , 22 ] might improve discard rates, it would require a long period of experimental verification. High-pressure inactivation, which Demazeau described as being effective against spores [ 23 ], is regarded by us to be a promising method for the future; as our group also found the technique effective on bacteria present in human and cow milk in the past [ 33 , 35 ].…”

Quantitative Risk Assessment of Bacillus cereus Growth during the Warming of Thawed Pasteurized Human Banked Milk Using a Predictive Mathematical Model

“…The methods of predictive microbiology are generally regarded to be a standard tool for assessing the risk of food, the properties of which are changing over time because of the presence of viable bacteria. We used this method in the past for predicting the growth of several microbes, including B. cereus, during the processing of human milk [ 35 ] and for evaluating thermo- and baro-inactivation of E. faecium and St. epidermidis in human and cow milk [ 36 , 37 ]. This paper applies this method to simulate manipulations with thawed PBM in neonatal hospital wards.…”

A DnaA‐dependent riboswitch for transcription attenuation of the his operon

“…The cell mixtures were grown in ABTGcasa medium at 37°C and diluted in fresh medium every 8–12 h. On days 4 and 7, each cell mixture was plated on LB agar in dilutions of 10 −2 , 10 −3 , 10 −4 , 10 −5 , and 10 −6 overnight at 37°C and the number of well‐separated colonies on each plate was counted the next day. The number of cells in each sample (10 μl) was calculated according to the following formula 57 : $$$N={\rm{\Sigma }}c/({n}_{1}+0.1{n}_{2})d$$$where N is the number of cells in a 10 μl sample; $$\phantom{\rule{}{0ex}}{\rm{\Sigma }}c$$ is the sum of colonies from plates for two consecutive dilutions, where at least one of the plates contains more than 15 colonies; $${n}_{1}$$ is the number of plates for the first selected dilution; $${n}_{2}$$ is the number of plates for the second selected dilution; and d is the dilution factor corresponding to the first dilution.…”