Quantitative Microbiological Risk Assessment Research Articles

Risk factors for listeriosis due to sausage consumption in Mexico: consumer practices, bacterial survival, and quantitative microbial risk assessment.

Listeriosis is a foodborne disease caused by Listeria monocytogenes (Lm), which represents a public health problem. Lm has been identified as an important contaminating bacterium of ready-to-eat meat products (RTEM) in Mexico. The objective was to explore the risk factors for acquiring listeriosis due to sausage consumption by defining the consumer profile, evaluating the survival of Lm in sausage (5, 10, and 25 °C for 32 days) and performing a quantitative microbiological risk assessment. The survey of 100 participants revealed that the factors compromising the safety of the RTEM by the consumer are the extension of the shelf life. Acquiring packaged RTEM was observed as a safe habit. All respondents stated that they were unaware of listeriosis, but 18% reported infections linked to RTEM, mainly sausage. The sausage supports the growth of Lm, whose population increases in congruence with temperature (25 °C > 10 °C >5 °C) and storage time (P ≤ 0.05). The increase in temperature decreases the adaptation time (Lag25 °C = 1.0 h, Lag10 °C= 92.5 h, Lag5 °C = 226.1 h) and increases the growth rate (μ25 °C = 4.43 CFU/h, μ10 °C = 0.075 CFU/h, μ5 °C = 0.0026 CFU/h) of Lm on the sausage. The risk of listeriosis due to sausage consumption increased according to the increase in temperature: 5.53 × 10-8-1.42 × 10-5 (5 °C), 0.00616-0.111 (10 °C), and 0.109-1.00 (25 °C). Consumer education in the hygienic management of RTEM and information on associated pathogens will minimize the risk of disease.

Quantitative microbiological spoilage risk assessment (QMSRA) of fresh poultry fillets during storage at retail

A quantitative microbiological spoilage risk assessment model (QMSRA) of aerobically stored fresh poultry fillets was developed based on pseudomonads growth and metabolic activity. Simultaneous microbiological and sensory analyses were performed in poultry fillets to evaluate the relation between pseudomonads concentration and sensory rejection due to spoilage. The analysis showed no organoleptic rejection at pseudomonads concentrations less than 6.08 log CFU/cm2. For higher concentrations, a “spoilage-response” relationship was developed using a beta-Poisson model. The above relationship was combined with a stochastic modeling approach for pseudomonads growth by taking into account both variability and uncertainty of factors affecting spoilage. To enhance the reliability of the developed QMSRA model, uncertainty was quantified and separated from variability using a second order Monte Carlo simulation. For a batch of 10,000 units, the QMSRA model predicted a median number of 11, 80, 295, 733 and 1,389 spoiled units for retail storage times of 6,7, 8, 9 and 10 days, respectively, while no spoiled units were predicted for storage time of up to 5 days at retail. Scenario analysis showed that a reduction of 1 log in the pseudomonads concentration at the time of packaging or 1 °C in retail storage temperature results in up to 90% reduction of the spoiled units while the combination of the above interventions can reduce the risk of spoilage by up to 99%, depending on the storage time. The poultry industry can utilize the QMSRA model as a transparent scientific basis to support food quality management decisions in determining appropriate expiration dates which maximize the utilization of the product’s “true” shelf life while minimize the risk of spoilage to an acceptable level. Furthermore, the scenario analysis can provide the necessary components for an effective cost-benefit analysis, enabling the identification and comparison of appropriate strategies for extending the shelf life of fresh poultry products.

Microbiological Risk Assessment and Its Use in Food Industry

Risk assessment is a novel approach, which is the estimation of the impact of hazards and the identification of components. The process in risk assessment is hazard identification, hazard characterisation, exposure assessment and risk characterisation. As a means of hazard evaluation, microbiological risk assessment links food and risk factors, such as food-borne bacteria, through data to predict their hazards relatively accurately and reliably, thereby reducing their impact on public health. This study mainly introduces the scientific information about risk assessment and the quantitative microbiological risk assessment in the instant food，mainly to evaluate the level of Listeria in foods. Meat products cause 60% of Listeria monocytogenes.

Survey of Domestic Refrigerator Storage Temperatures in Poland for Use as a QMRA Tool for Exposure Assessment

In the framework of Quantitative Microbiological Risk Assessment, the estimation of the ingested dose of a hazard by the consumer is of paramount importance. This may be calculated by means of predictive modeling of growth/inactivation of the pathogen studied. For products that spend the majority of their shelf life in the domestic refrigerator, storage temperature will significantly impact the microbial population dynamics. To describe the variability of domestic storage temperatures in Poland, a survey including 77 participants, was carried out in Lodz, Poland. Participants were provided with temperature data loggers, which measured their refrigerator temperature for 24 h in 5-min intervals. The temperature-time profiles were used to calculate the mean working temperature, standard deviation, minimum and maximum values, and the data were statistically analyzed to find the best fitting probability distribution using R programming language. Out of the tested refrigerators, 49.35% had a mean working temperature of over 5 °C and 3.9% exceeded 10 °C. Distribution fitting scenarios were tested for goodness of fit, and the final selected distribution was a truncated normal distribution. This study can prove useful in Monte Carlo simulation analysis for stochastic quantitative food risk assessment in Poland.

Risk Reduction Assessment of Vibrio parahaemolyticus on Shrimp by a Chinese Eating Habit

In China, a traditional perspective recommended that consuming seafood should be mixed or matched with vinegar, because people thought this traditional Chinese eating habit could reduce the risk of pathogenic microorganism infection, such as Vibrio parahaemolyticus induced diarrhea. However, this empirical viewpoint has not yet been evaluated scientifically. This study conducted a simplified quantitative microbiological risk assessment (QMRA) model, which was employed to estimate the risk reduction of V. parahaemolyticus on ready-to-eat (RTE) shrimp by consuming with vinegars (white vinegar, aromatic vinegar, or mature vinegar). Results showed the reduction of V. parahaemolyticus density on RTE shrimp after consuming with white vinegar, aromatic vinegar and mature vinegar was respectively 0.9953 log CFU/g (90% confidence interval 0.23 to 1.76), 0.7018 log CFU/g (90% confidence interval 0.3430 to 1.060) and 0.6538 log CFU/g (90% confidence interval 0.346 to 0.9620). The infection risk of V. parahaemolyticus per meal in this QMRA model was quantified by a mean of 0.1250 with the standard deviation of 0.2437. After consuming with white vinegar, aromatic vinegar, and mature vinegar, the mean infection risk of V. parahaemolyticus on shrimp decreased to 0.0478, 0.0652, and 0.0686. The QMRA scenarios indicated significant reductions in infection risk when eating RTE shrimp by the Chinese eating habit (consuming with vinegar). This good eating habit should be recommended to promote the spread of around the world.

Quantitative risk assessment for type A staphylococcal enterotoxin poisoning due to consumption of Minas Frescal cheese in Brazil

This study aimed to estimate the risk of staphylococcal toxin type A (SEA) poisoning from consuming Minas Frescal cheese (MFC) in Brazil. A Quantitative Microbiological Risk Assessment model was developed, focussing on the production of SEA while still in the raw material. The baseline scenario yielded a simulated mean concentration of SEA in the MFC portion of 16.20 ng. The concentration of Staphylococcus aureus in raw milk is proved to be the most influential parameter for the risk, followed by the serving size and the prevalence of toxin genes.

Quantitative microbiological risk assessment of traditional food of animal origin produced in short supply chains in Poland.

Polish raw-milk cheeses produced in short supply chains may pose a threat to consumer safety due to pathogen presence. Listeria monocytogenes is a bacterium of great importance for the food safety of refrigerated RTE foods due to its ability to grow at refrigeration temperatures. During the EU-FORA fellowship, a stochastic risk assessment was designed and executed to estimate the risk for consumers from L. monocytogenes in these products. The aim was to develop a probabilistic QMRA model that would incorporate the variability and uncertainty of the model's inputs such as prevalence, initial concentration levels, product intrinsic factors, domestic storage temperature and consumer behaviour. The project involved data collection and analysis, growth model selection, mathematical modelling and Monte Carlo analysis in R programming language. Microbiological and physicochemical testing were carried out throughout the year on two types of cheeses in combination with a domestic refrigerator temperature survey and accompanying consumption questionnaire. Collected data were fitted to probability distributions using R. The appropriate growth model for the pathogen was selected based on an inoculation study performed on one of the raw-milk cheeses and the chosen mathematical model was written into the R script developed for the QMRA. The dose-response model used the ingested dose calculated from the modelled concentration of L. monocytogenes at the time of consumption and the single serving size from the questionnaire to estimate the probability of illness. The final risk was expressed as probability of listeriosis for Polish consumers per serving of raw-milk cheese.

Prevalence and concentration of Campylobacter in faeces of dairy cows: A systematic review and meta-analysis.

The consumption of raw milk from dairy cows has caused multiple food-borne outbreaks of campylobacteriosis in the European Union (EU) since 2011. Cross-contamination of raw milk through faeces is an important vehicle for transmission of Campylobacter to consumers. This systematic review and meta-analysis, aimed to summarize data on the prevalence and concentration of Campylobacter in faeces of dairy cows. Suitable scientific articles published up to July 2021 were identified through a systematic literature search and subjected to screening and quality assessment. Fifty-three out of 1338 identified studies were eligible for data extraction and 44 were further eligible for meta-analysis. The pooled prevalence was calculated in two different meta-analytic models: a simple model based on one average prevalence estimate per study and a multilevel meta-analytic model that included all prevalence outcomes reported in each study (including different subgroups of e.g. health status and age of dairy cows). The results of the two models were significantly different with a pooled prevalence estimate of 29%, 95% CI [23–36%] and 51%, 95% CI [44–57%], respectively. The effect of sub-groups on prevalence were analyzed with a multilevel mixed-effect model which showed a significant effect of the faecal collection methods and Campylobacter species on the prevalence. A meta-analysis on concentration data could not be performed due to the limited availability of data. This systematic review highlights important data gaps and limitations in current studies and variation of prevalence outcomes between available studies. The included studies used a variety of methods for sampling, data collection and analysis of Campylobacter that added uncertainty to the pooled prevalence estimates. Nevertheless, the performed meta-analysis improved our understanding of Campylobacter prevalence in faeces of dairy cows and is considered a valuable basis for the further development of quantitative microbiological risk assessment models for Campylobacter in (raw) milk and food products thereof.

Critical comparison of statistical methods for quantifying variability and uncertainty of microbial responses from experimental data

Variability and uncertainty are important factors for quantitative microbiological risk assessment (QMRA). In this context, variability refers to inherent sources of variation, whereas uncertainty refers to imprecise knowledge or lack of it. In this work we compare three statistical methods to estimate variability in the kinetic parameters of microbial populations: mixed-effect models, multilevel Bayesian models, and a simplified algebraic method previously suggested. We use two case studies that analyse the influence of three levels of variability: (1) between-strain variability (different strains of the same species), (2) within-strain variability (biologically independent reproductions of the same strain) and, at the most nested level, (3) experimental variability (species independent technical lab variability resulting in uncertainty about the population characteristic of interest) on the growth and inactivation of Listeria monocytogenes. We demonstrate that the algebraic method, although relatively easy to use, overestimates the contribution of between-strain and within-strain variability due to the propagation of experimental variability in the nested experimental design. The magnitude of the bias is proportional to the variance of the lower levels and inversely proportional to the number of repetitions. This bias was very relevant in the case study related to growth, whereas for the case study on inactivation the resulting insights in variability were practically independent of the method used. The mixed-effects model and the multilevel Bayesian models calculate unbiased estimates for all levels of variability in all the cases tested. Consequently, we recommend using the algebraic method for initial screenings due to its simplicity. However, to obtain parameter estimates for QMRA, the more complex methods should generally be used to obtain unbiased estimates.

Quantitative Risk Assessment of Vibrio parahaemolyticus in Shellfish from Retail to Consumption in Coastal Cities of Eastern China

Vibrio parahaemolyticus is the main foodborne pathogen worldwide that causes acute gastroenteritis. A quantitative microbiological risk assessment (QMRA) was conducted to evaluate the health risk associated with V. parahaemolyticus in shellfish in the coastal cities in the eastern part of the People's Republic of China. The QMRA framework was established from shellfish at retail to cooking at home to consumption. The prevalence and level of V. parahaemolyticus in shellfish, cooking methods, storage temperature, time after purchase, shellfish consumption frequency, and consumption amount were analyzed in the exposure assessment. The results of the exposure assessment were introduced into the beta-Poisson dose-response model, and Monte Carlo analysis was used to calculate the risk of gastroenteritis from shellfish consumption. The probability of illness caused by V. parahaemolyticus from shellfish consumption per person per year (Pill,yr) was 3.49E-05. Seasonal differences were noted in the Pill/meal; the maximum was 4.81E-06 in summer and the minimum was 2.27E-07 in winter. The sensitivity analysis revealed that the level of V. parahaemolyticus in shellfish and the amount of shellfish consumed per meal were main factors contributing to illness. This QMRA provided valuable information such as the probability of illness associated with the consumption of shellfish and reference points for prevention strategies and control standards of V. parahaemolyticus in shellfish.

Characterization of Listeria monocytogenes biofilm formation kinetics and biofilm transfer to cantaloupe surfaces

Listeria monocytogenes biofilm is a consistent source of cross-contamination, both in housing storage and food processing environments. This study monitored the dynamic process of L. monocytogenes ST9 and ST87 biofilms, as well as their cross-contamination behaviors at various stages of formation. Scanning Electron Microscopy (SEM) captured the honeycomb-like structures and extracellular polymeric substances (EPS) during the biofilm formation. Confocal Laser Scanning Microscopy (CLSM) images illustrated that the ST87 strain formed a closed knitted chains network later than the ST9 strain. Moreover, structural parameters including bio-volume, mean thickness, porosity, and roughness could quantified the spatio-temporal differences of the biofilms. The transfer rates of biofilm cells to cantaloupes with the single contact had no significant difference at the initial adhesion, maturation, and dispersion stage (p > 0.05). Notably, the biofilm cells remained on the glass coupons when transferred to ten cantaloupe slices, indicating that biofilm cells transferred through cohesive failure. Meanwhile, the Logistic model could describe the transfer law of biofilm cells at different formation stages, as evaluated by Root Mean Square Error (RMSE) and R2adj. Additionally, the transfer rates were positively correlated with the hydrophobicity of L. monocytogenes ST87 biofilm cells measured by xylene. However, when the hydrophobicity of n-hexadecane was measured, the correlation was negative. This study illustrated the spatial and temporal differences during L. monocytogenes biofilms formation, and the transfer and residual of biofilm cells after a single and ten successive contacts at the specific stages. Our findings help in the quantitative microbiological risk assessment of fresh produce.

A quantitative risk assessment of Listeria monocytogenes from prevalence and concentration data: Application to a traditional ready to eat (RTE) meat product

Ready to Eat (RTE) cooked meat products are among the most consumed RTE food subcategories in the EU/EEA. They are also associated with the highest number of identified listeriosis cases per year (>850), thus posing a public health risk especially among the susceptible population. This study estimated the risk of listeriosis from Italian head cheese (Coppa di Testa) consumption using a Quantitative Microbiological Risk Assessment (QMRA) based on data of prevalence and starting concentrations of Listeria monocytogenes in the product during a 3-year period (n = 1568). A consumer survey (n = 162) was conducted to provide information on domestic storage time and consumption habits, and storage conditions were determined from recordings of temperatures of domestic refrigerators (n = 57). A probabilistic model was designed for the evaluation of the growth of L. monocytogenes at each stage of the product pathway from production to consumption, using Monte Carlo simulations and employing the @Risk software. Risks associated to consumption of vacuum-packed and sliced-at-retail head cheese were assessed: The model predicted that the risk of listeriosis per serving of vacuum-packed product was in the 10−4 and 10−6 range (mean) for the high-risk and general populations respectively, and listeriosis cases were estimated to be greater than those due to consumption of sliced product (with risks in the range of 10−7 and 10−8). Overall, the model predicted that the mean number of listeriosis cases ranged from 0.001 to 0.24 and from 0.06 to 10 per one hundred thousand people, for the healthy and the high-risk population, respectively. Scenario analyses indicated that better control of the temperature of domestic refrigerators is effective in reducing the predicted risk of listeriosis for the longer stored vacuum-packed product by ~80 % for both the healthy and high-risk populations, whereas a shorter use-by-date of 30 days is an effective risk mitigation measure for both types of packed product. Model assumptions, as well as data gaps are discussed.

Quantitative microbiological risk assessment of nontyphoidal Salmonella in ground pork in households in Chengdu, China.

Foodborne disease caused by nontyphoidal Salmonella (NTS) is one of the most important food safety issues worldwide. The objectives of this study were to carry out microbial monitoring on the prevalence of NTS in commercial ground pork, investigate consumption patterns, and conduct a quantitative microbiological risk assessment (QMRA) that considers cross-contamination to determine the risk caused by consuming ground pork and ready-to-eat food contaminated during food handling in the kitchen in Chengdu, China. The food pathway of ground pork was simplified and assumed to be several units according to the actual situation and our survey data, which were collected from our research or references and substituted into the QMRA model for simulation. The results showed that the prevalence of NTS in ground pork purchased in Chengdu was 69.64% (95% confidence interval [CI], 60.2-78.0), with a mean contamination level of -0.164 log CFU/g. After general cooking, NTS in ground pork could be eliminated (contamination level of zero). The estimated probability of causing salmonellosis per day was 9.43E-06 (95% CI: 8.82E-06-1.00E-05), while the estimated salmonellosis cases per million people per year were 3442 (95% CI: 3218-3666). According to the sensitivity analysis, the occurrence of cross-contamination was the most important factor affecting the probability of salmonellosis. To reduce the risk of salmonellosis caused by NTS through ground pork consumption, reasonable hygiene prevention and control measures should be adopted during food preparation to reduce cross-contamination. This study provides valuable information for household cooking and food safety management in China.

Antibiotics and antibiotic-resistant bacteria in greywater: Challenges of the current treatment situation and predictions of future scenario

The current work reviews the quantitative microbiological risk assessment of antibiotic-resistant bacteria (ARB) in greywater and discusses the international strategies currently used for reducing antimicrobial resistance. The work highlights the countries that have a plan for the treatment and reuse of greywater and the current guidelines used in these countries. The paper also investigates the role of greywater in the distribution of antimicrobial resistance because of antibiotics and ARB. A bibliometric analysis was conducted for the studies on greywater, pathogenic bacteria, and antibiotics. The studies obtained from Scopus database were screened and compared to obtain the data for global antimicrobial resistance in 2000 and 2021. The strategies used by developed countries that led to the reduction in the recorded antimicrobial resistance are also listed. The challenges and limitations associated with the current plans adopted by several countries to minimise the spreading of the antimicrobial resistance are highlighted, while proposed solutions are provided. Two main issues associated with the distribution of antimicrobial resistance are (1) the absence of a plan in developing counties and presence of antimicrobial agents and ARB in the environment and (2) the difficulties in the current treatment technologies used for the removal of these antimicrobial agents from the water and wastewater. Based on the review and discussion, it was concluded that more advanced technologies are required to ensure total elimination of the antimicrobial agents and ARB from the environment. In addition, a new international standard should be drafted for the ARB in the environment, as they differ from the one currently used for medical applications.

Landscape of Stress Response and Virulence Genes Among Listeria monocytogenes Strains.

The pathogenic microorganism Listeria monocytogenes is ubiquitous and responsible for listeriosis, a disease with a high mortality rate in susceptible people. It can persist in different habitats, including the farm environment, the food production environments, and in foods. This pathogen can grow under challenging conditions, such as low pH, low temperatures, and high salt concentrations. However, L. monocytogenes has a high degree of strain divergence regarding virulence potential, environmental adaption, and stress response. This review seeks to provide the reader with an up-to-date overview of clonal and serotype-specific differences among L. monocytogenes strains. Emphasis on the genes and genomic islands responsible for virulence and resistance to environmental stresses is given to explain the complex adaptation among L. monocytogenes strains. Moreover, we highlight the use of advanced diagnostic technologies, such as whole-genome sequencing, to fine-tune quantitative microbiological risk assessment for better control of listeriosis.

A hierarchical Bayesian quantitative microbiological risk assessment model for Salmonella in the sheep meat food chain

Multiple foodborne routes of Salmonella infection have been observed; however, the majority of the literature to date has been dominated by research into the most frequently observed reservoirs, such as chicken, beef, and pork. While less commonly observed, outbreaks of Salmonella within sheep meat still occur, requiring extensive investigation by food safety inspectors. Risk assessment models inform policy makers and investigators of the risks posed by pathogens at each stage of the food chain, and help suggest at which stages in the food chain outbreaks are likely induced. This work is the first risk assessment into the prevalence of Salmonella throughout the sheep meat food chain, from farm to fork. A Bayesian evidence-synthesis model is used, informed by data gathered from 27 individual studies - an exhaustive search of the existing literature, to express and enumerate the current understanding of Salmonella prevalence in the sheep meat food chain in the form of probabilities of colonisation throughout the food chain. The resulting posterior estimate projects that 9 (0–29 95% HDI) UK individuals are likely to fall ill with salmonellosis due to sheep meat every year. A variance-based sensitivity analysis reveals that the abattoir module is the stage of greatest bacterial proliferation, highlighting it as the most probable source of outbreaks, though not to the exclusion of other factors.

Risk of Waterborne Parasitic Infection among Vegetables Producers in the City of Ouagadougou, Burkina Faso: An Attempt to Quantify Them Using the Quantitative Microbiological Risk Assessment Method

The use of wastewater in urban agriculture has been promoted as an alternative to water scarcity and as a means to increase soil fertilizer. However, the use of wastewater in urban agriculture raises major public health concerns, mainly due to the often high concentration of pathogenic micro-organisms. Waterborne parasites are a major health concern in this regard, especially in endemic areas, mainly due to the high environmental resistance of eggs/cysts combined with a low infectious dose. In this study, the parasitological risk to vegetables producers in Ouagadougou using polluted water was evaluated through the quantitative microbiological risk analysis method. For this purpose, the search for and quantification of viable parasite eggs and cysts in irrigation water was coupled with epidemiological surveillance of vegetables producers in Ouagadougou. Protozoa and helminths belonging to 9 species were recorded and samples analyzed. These include Ancylostoma sp., Ascaris lumbricoides, tapeworm’s sp, Strongyloides stercoralis, Entamoeba histolytica, Giardia lamblia. Despite the variability of isolated parasitic species, Ancylostoma sp. eggs were common and severe to all types of water. Moreover, epidemiological approach showed that there were more parasitic species found in irrigation water and also other parasitic species circulating among vegetable farmers. In addition, there is no statistical significant association between the type of water used for irrigation and the carried parasites by vegetable gardeners. However, contamination of the groups using the raw wastewater is once higher than those using well water. When one is interested in the groups using treated wastewater as a source of irrigation, these risks of contaminations are halved. These contaminations are halved when one looks at groups using treated wastewater as a source of irrigation water. Still, whatever the type of water used by the gardeners, they have a probability of infection with Ancylostoma sp. of around 9.83 × 10−1 pppy.

Seawater desalination based drinking water: Microbial characterization during distribution with and without residual chlorine

Monitoring the changes that occur to water during distribution is vital to ensure water safety. In this study, the biological stability of reverse osmosis (RO) produced drinking water, characterized by low cell concentration and low assimilable organic carbon, in combination with chlorine disinfection was investigated. Water quality at several locations throughout the existing distribution network was monitored to investigate whether microbial water quality changes can be identified. Results revealed that the water leaving the plant had an average bacterial cell concentration of 103 cells/mL. A 0.5–1.5 log increase in bacterial cell concentration was observed at locations in the network. The residual disinfectant was largely dissipated in the network from 0.5 mg/L at the treatment plant to less than 0.1 mg/L in the network locations. The simulative study involving miniature distribution networks, mimicking the dynamics of a distribution network, fed with the RO produced chlorinated and non-chlorinated drinking water revealed that distributing RO produced water without residual disinfection, especially at high water temperatures (25–30 °C), poses a higher chance for water quality change. Within six months of operation of the miniature network fed with unchlorinated RO produced water, the adenosine triphosphate (ATP) and total cell concentration (TCC) in the pipe biofilm were 4 × 102 pg ATP/cm2 and 1 × 107 cells/ cm2. The low bacterial cell concentration and organic carbon concentration in the RO-produced water did not prevent biofilm development inside the network with and without residual chlorine. The bacterial community analysis using 16S ribosomal RNA (rRNA) gene sequencing revealed that mesophilic bacteria with higher temperature tolerance and bacteria associated with oligotrophic, nutrient-poor conditions dominated the biofilm, with no indication of the existence of opportunistic pathogenic species. However, chlorination selected against most bacterial groups and the bacterial community that remained was mainly the bacteria capable of surviving disinfection regimes. Biofilms that developed in the presence of chlorine contained species classified as opportunistic pathogens. These biofilms have an impact on shaping the water quality received at the consumer tap. The presence of these bacteria on its own is not a health risk indicator; viability assessment and qPCRs targeting genes specific to the opportunistic pathogens as well as quantitative microbiological risk assessment (QMRA) should be included to assess the risk.The results from this study highlight the importance of implementing multiple barriers to ensure water safety. Changes in water quality detected even when high-quality disinfected RO-produced water is distributed highlight microbiological challenges that chlorinated systems endure, especially at high water temperatures.

An updated assessment of the effect of control options to reduce Campylobacter concentrations in broiler caeca on human health risk in the European Union

Quantitative microbiological risk assessment (QMRA) studies have suggested that control options to reduce the concentration of Campylobacter spp. in broiler chicken caeca may be highly effective at reducing the risk of human campylobacteriosis. These QMRA studies have been updated based on scientific evidence obtained in the past decade. The relationship between Campylobacter concentrations in the caeca and on broiler skins after industrial processing was modelled by means of linear regression and combined with a number of consumer phase models (CPM) and dose-response (DR) models. The reduction of caecal Campylobacter concentration as reported for selected feed additives and vaccines, was used to estimate the relative risk reduction expressed as the percentage decrease in human campylobacteriosis cases in the EU associated with consumption of broiler meat. The model outputs suggest that the effectiveness of these control options are less pronounced than previously indicated. For example, the median estimate for the relative risk reduction obtained through a 2 log10 reduction in caecal concentrations was 39% (95% CI 9–73%), whereas previous estimates were between 76 and 98%. The main reason for this finding is that recent studies show lower values for the slope of the regression line; the impact of using newly published DR models and CPMs is smaller. Still, the uncertainty associated to the estimated effects is large, mainly due to uncertainty about the slope of the regression line. Additionally, data on the effectiveness of vaccination and the application of feed and water additives obtained under field conditions are scarce, but they are a prerequisite to assess the risk reduction that may be achieved by these control options when applied in practice.

Solar processes and ozonation for fresh-cut wastewater reclamation and reuse: Assessment of chemical, microbiological and chlorosis risks of raw-eaten crops

In this study, a full cycle of agricultural reuse of agro-food wastewater (synthetic fresh-cut wastewater, SFCWW) at pilot plant scale has been investigated. Treated SFCWW by ozonation and two solar processes (H2O2/solar, Fe3+-EDDHA/H2O2/solar) was used to irrigate two raw-eaten crops (lettuce and radish) grown in peat. Two foodborne pathogens (E. coli O157:H7 and Salmonella enteritidis) and five organic microcontaminants (OMCs: atrazine, azoxystrobin, buprofezin, procymidone and terbutryn) were monitored along the whole process. The three studied processes showed a high treatment capability (reaching microbial loads < 7 CFU/100 mL and 21-90 % of OMC reduction), robustness (based on 7 or 10 analysed batches for each treatment process) and high suitability for subsequent treated SFCWW safe reuse: non-phytotoxic towards Lactuca sativa and no bacterial regrowth during its storage for a week. The analysis of the harvested crop samples irrigated with treated SFCWW in all the studied processes showed an absence of microbial contamination (< limit of detection, LOD; i.e., < 1 CFU/99 g of lettuce and < 1 CFU/8 g of radish), a significant reduction of OMC uptake (in the range 40-60 % and > 90 % for solar treated and ozonated SFCWW, respectively) and bioaccumulation in both crops in comparison with the results obtained with untreated SFCWW. Moreover, the chlorophyll content in the harvested lettuces irrigated with SFCWW treated by Fe3+-EDDHA/H2O2/solar was twice than that irrigated with SFCWW treated by H2O2/solar and ozone, indicating the additional advantage of using Fe3+-EDDHA as an iron source to reduce the risk of iron chlorosis in crops. Finally, the chemical (dietary risk assessment for the combined exposure of the 5 OMCs) and quantitative microbiological risk assessment (QMRA) of the harvested crops showed the capability of the studied processes to reduce the risk associated with untreated SFCWW reuse by more than 50 % and more than 4 orders of magnitude, respectively.