Category Archives: Enterococcus

Research- Predictive microbial modeling of E. faecium NRRL B-2354 inactivation during baking of a multi-component low-moisture food

Journal of Food Protection

Validating baking ovens as a microbial kill step, using thermal inactivation models, is desirable; however, traditional isothermal models may not be appropriate for these dynamic processes, yet they are being used by the food industry. Previous research indicates that the impact of additional process conditions, such as process humidity, should be considered when validating thermal processes for the control of microbial hazards in low-moisture foods. In this study, the predictive performance of traditional and modified thermal inactivation kinetic models accounting for process humidity were assessed for predicting bacterial inactivation of Enterococcus faecium NRRL B-2354 in a multi-ingredient composite food during baking. Ingredients (milk powder, protein powder, peanut butter, and whole wheat flour), individually inoculated to ~6 logCFU/g and equilibrated to a water activity of 0.25, were mixed to form a dough. An isothermal inactivation study was conducted for the dough to obtain traditional D- and z- values (n=63). In a separate experiment, cookies were baked under four dynamic heating conditions: 135℃/high humidity, 135℃/low humidity, 150℃/high humidity, and 150℃/low humidity. Process humidity measurements, time-temperature profiles for the product core, surface, and bulk air, and microbial survivor ratios were collected for the four conditions at six residence times (n=144). The traditional isothermal model had a poor root mean square error (RMSE) of 856.51 log (CFU/g), significantly overpredicting bacterial inactivation during the process. The modified model accounting for the dynamic time-temperature profile and process humidity data yielded a better predictive performance with a RMSE of 0.55 log CFU/g. The results demonstrate the importance of accounting for additional process parameters in baking inactivation models, and that model performance can be improved by utilizing model parameters obtained directly from industrial-scale experimental data.

Research – Thermal Inactivation Kinetics of Salmonella and Enterococcus faecium NRRL-B2354 on whole chia seeds (Salvia hispanica L.)

Journal of Food Protection

Intervention technologies for inactivating Salmonella in whole chia seeds are currently limited. The determination of the thermal inactivation kinetics of Salmonella o n chia seeds and selection of an appropriate nonpathogenic surrogate will provide a knowledge foundation for selecting and optimizing thermal pasteurization processes for chia seeds. In this study, chia seed samples from three separate production lots were inoculated with a five strain Salmonella cocktail or Enterococcus faecium NRRL-B2354 and equilibrated to 0.53 aw at room temperature (25 °C). After equilibration for at least three days, the inoculated seeds were subjected to isothermal treatments at 80, 85, or 90 °C. Samples were taken out at six timepoints and enumerated for survivors. Initial dilution of whole chia seeds was performed in a filter bag at a 1:30 ratio after it was shown to have similar recovery to grinding the seeds. Survivor data were fitted to consolidated models consisting of a primary model (log-linear or Weibull) and one secondary model (Bigelow). E. faecium exhibited higher thermal resistance than Salmonella , suggesting its suitability as a conservative nonpathogenic surrogate. The Weibull model was a better fit for the survivor data than the log-linear model for both bacteria due to its lower root mean square error and corrected Akaike’s Information Criterion values. Measurements of lipid oxidation and fatty acid content indicated a few statistically different values compared to the control samples, but the overall difference in magnitudes were relatively small. The thermal inactivation kinetics of Salmonella and E. faecium o n chia seeds as presented in this study can serve as a basis for developing thermal pasteurization processes for chia seeds.

Research – Microbial Safety of Smoothie Drinks from Fresh Bars Collected in Slovakia


Among the many consumers in Slovakia, smoothies are nowadays gaining popularity. Smoothie drinks are prepared from raw fruits and vegetables. Therefore, their microbiological safety depends on hygiene standards. The aim of this work was to monitor and quantify selected sensitive and antibiotic-resistant microorganisms present in collected smoothies. Twenty analyzed smoothie samples were collected from six food service establishments (fresh bars) in the capital city of Slovakia, Bratislava. Antibiotic-resistant bacteria were found in at least one of each fresh bar. Antibiotic-resistant coliform bacteria prevailed, especially in green smoothies or juices containing more vegetable ingredients. Resistance to ampicillin, ciprofloxacin, tetracycline, chloramphenicol, and gentamicin was observed in the case of coliform bacteria. More than half of the smoothie drink samples did not contain resistant enterococci. On the other hand, vancomycin-resistant enterococci were detected in 20% of samples. The most frequently isolated antibiotic-resistant strains belonged to the Enterobacter spp. or Klebsiella spp. genus. In the last part of the work, the pretreatment effect of smoothie components on the selected microorganisms’ counts in the final product was investigated. Washing ingredients with an aqueous solution of a biocide agent containing silver and hydrogen peroxide proved to be the most effective way to decrease bacterial counts. View Full-Text

Research – Microbial analysis and factors associated with contamination of ready-to-eat chili pepper sauce in Buea municipality, Cameroon


Chili peppers sauce is a dietary complement largely consumed in Cameroon. It is consumed in a powder or wet (pepper sauce) form or directly introduced into cooked food. In this study, the microbiological quality of chili pepper sauce used as food complement in the Buea municipality was assessed. The study was an observational and cross-sectional study involving 70 chili pepper sauce samples from food vendors. The samples were cultured on Salmonella-Shigella agar, violet red bile agar, plate count agar and the colonies isolated were enumerated and identified using the Enterosystem 18R. Factors associated with microbial count were identified using a multiple linear regression model. Bacteria isolate from chili pepper sauce were mainly Entrobacter cloacae (31.57%), Citrobacter freundii (15.78%) and Klebsiella pneumonia (15.78%) and other Enterococcal speciesFactors associated with bacteria count were: age of the vendor, number of customers served, types of food and food storage conditions (covering, heating, type of storage containers). Chili pepper sauce used as food complement in Buea Municipality were contaminated with Enteric microorganisms and may represents a potential public health hazard to consumers. The presence of these microorganisms from chilli pepper sauce could result from poor handling.

RASFF Alert- Animal Feed – unauthorised ingredients in fish feed

European Food Alerts


unauthorised ingredients (Lactobacillus plantarum, Enterococcus faecalis, Pediococcus lactis) in fish feed from China in the UK

Research – Evaluation of Hot-air Drying to Inactivate Salmonella spp. and Enterococcus faecium on Apple Pieces

Journal of Food Protection

Hot-air drying processes are used to provide specific quality attributes to products, such as dehydrated apple pieces. To comply with the U. S. Food and Drug Administration Food Safety Modernization Act, there is a need to understand microbial lethality during these processes. The objective of this study was to determine the level of inactivation provided by hot-air drying on a Salmonella cocktail inoculated onto apple cubes and to evaluate the performance of Enterococcus faecium as a surrogate. A Salmonella cocktail ( S. Agona, S. Tennessee, S. Montevideo, S. Mbandaka and S. Reading) and E. faecium were individually inoculated onto cored, peeled Gala apple cubes at 9.2 ± 0.3 and 8.8 ± 0.1 log CFU/sample, respectively . Apple cubes were dried at 104°C or 135°C in ~1.5 kg batches using a hot-air dryer with a vertically directed heat source and without mixing. Three subsamples, consisting of 4 inoculated cubes, were enumerated at each time point (n ≥ 5) from multiple product bed depths. Water activity decreased throughout the duration of the study with samples at 135°C drying faster than 104°C. Samples at the bottom bed depth, closer to the heat source, dried faster than those at the higher bed depth, regardless of temperature. Significant microbial inactivation was not seen immediately. It took >10 min at the bottom bed depth or > 40 min of drying at the top bed depth, regardless of temperature (p < 0.05).  By the end of drying average Salmonella inactivation of greater than 5 log CFU/sample was achieved. At temperature conditions evaluated, E. faecium inactivation was slower than Salmonella , indicating that it would likely serve as a good surrogate for in-plant validation studies. Case hardening did not inhibit microbial inactivation in the conditions tested. Hot-air drying under the conditions evaluated may provide a preventive control in the production of dehydrated products, such as apples.

Research – Thermal Resistance of Foodborne Pathogens and Enterococcus faecium NRRL B-2354 on Inoculated Pistachios


Process control validations require knowledge of the resistance of the pathogen(s) of concern to the target treatment, and, in some cases, the relative resistance of surrogate organisms. Selected strains of Escherichia coli O157:H7 (five strains), Listeria monocytogenes (five strains), and Salmonella enterica (five strains) as well as Salmonella Enteritidis phage type (PT) 30 and nonpathogenic Enterococcus faecium NRRL B-2354 were inoculated separately (as individual strains) onto inshell pistachios. The thermal tolerance of each strain was compared via treatment of inoculated pistachios to hot oil (121°C) or hot water (80°C) for 1 min. Survivor curves in hot oil or hot water (0.5 to 6 min, n = 6 to 15) were determined for one or two of the most resistant strains of each pathogen, as well as E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30, and the Weibull model was fit to the data. A pilot-scale air-impingement oven was used to compare the thermal tolerance of E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30 on pistachios with or without a brining pretreatment and at either dry (no steam) or 30% humidity (v/v) oven conditions. No significant difference in the time to a 4-log reduction in hot oil or hot water was predicted for any of the strains evaluated, on the basis of the 95% confidence interval. In the pilot-scale oven, E. faecium NRRL B-2354 was more thermally resistant than Salmonella in a broad set of differing treatments, treatment times, and temperatures. Salmonella is a suitable target pathogen of concern in pistachios for thermal processes because no other pathogen tested was more thermally resistant under the conditions evaluated. E. faecium NRRL B-2354 was at least as thermally resistant as Salmonella under all conditions evaluated, making it a good potential surrogate for Salmonella on pistachios.

Research – Microbial contamination of grocery shopping trolleys and baskets in west Texas, 2020

Barf Blog

Indicator microorganisms evaluated were those detected by aerobic plate count (APC), yeast and molds (YM), Enterobacteriaceae (EB). Environmental listeria (EL), coliforms (CF), and E. coli (EC).  In addition, listeria monocytogenes, staphylococcus aureus, Escherichia coli O157 and salmonella sp. Were tested for.  Trolley grills (n=36) had 2.7 x 10CFU/cm2.  Trolley handles (n=36) had 2.7 x 10of CF and 5.2 CFU/cm2 of YM.  The bottom of handheld baskets (n=25) had 3.5 x 105 CFU/cm2 of CF and 5.07 CFU/cmof EC.  S. aureus was found on 96% of the baskets, 50% of the trolley handles (18 out of 36 samples), and 42% of the trolleys’ grills.  E. coli O157 was identified on 17% of baskets, 3% on trolley grills, and 3% on handles.  Salmonella sp. was detected on 16% of baskets and 8% of trolley grills.  L. monocytogenes was detected on 17% of the bottoms of handheld baskets but on none of the other samples. 

Research -Radiofrequency pasteurization process for inactivation of Salmonella spp. and Enterococcus faecium NRRL B-2354 on ground black pepper

Science Direct


Salmonella persistence in ground black pepper has caused several foodborne outbreaks and created public concern about the safety of low water activity (aw) foods. In this study, radiofrequency (RF) processing was evaluated for pasteurization of ground black pepper. Stability and homogeneity tests were done for both Salmonella spp. and E. faecium during moisture equilibration before RF heating to evaluate the inoculation method. Moisture content of samples were conditioned such that the final moisture content after RF heating reached the optimal storage moisture. RF heating was shown to provide more than 5.98 log CFU/g reduction for Salmonella spp. and the reduction of 3.89 log CFU/g for E. faecium with a 130 s of treatment time. The higher thermal resistance of E. faecium indicated its suitability as surrogate for Salmonella spp. during RF heating of ground black pepper. Piperine, total phenolics, volatile compounds, and antioxidant activity were assessed as quality parameters for ground black pepper. The results demonstrated that the RF processing provided effective inactivation of Salmonella spp. with insignificant (p > 0.05) quality deterioration.

RASFF Alert -Escherichia coli -Pseudomonas aeruginosa – Enterococcus – Still and Sparkling Bottled Water


RASFF – Escherichia coli, Pseudomonas aeruginosa (>100 CFU/250ml) and Enterococcus in still and sparkling bottled water from Ireland in Ireland