The prevalence of Listeria monocytogenes in meat products in China: A systematic literature review and novel meta-analysis approach.

Meat products are commonly regarded as one of the main sources of human listeriosis caused by Listeria monocytogenes. The objective of this study was to estimate the prevalence of L. monocytogenes in a range of meat products from 24 different Chinese regions by using meta-analysis of literature data and a novel sensitivity analysis approach. A total of 112 publications from five databases, published between 1 January 2007 and 31 December 2017, were systematically selected for relevance and covered meat products sampled between 2000 and 2016. Estimated by the random-effects model, the pooled prevalence of L. monocytogenes was 8.5% (95% CI: 7.1%-10.3%) in raw meats and 3.2% (95% CI: 2.7%-3.9%) in ready-to-eat (RTE) meats. The prevalence differed from high to low among raw meats including prefabricated raw meats 12.6% (95% CI: 6.9%-21.7%), fresh pork 11.4% (95% CI: 8.6%-14.9%), fresh beef 9.1% (95% CI: 6.3%-13.0%), fresh poultry 7.2% (95% CI:4.9%-10.4%), frozen raw meats 7.2% (95% CI: 5.7%-9.0%), and fresh mutton 5.4% (95% CI: 2.5%-11.0%). A higher L. monocytogenes prevalence level was shown in the meat products from central and northeastern China provincial regions. The entropy-based sensitivity analysis utilized in the meta-analysis indicated that the sampling period and location were two critical factors influencing the prevalence level of L. monocytogenes in meat products. A better understanding of differences in prevalence levels per geographic region and between meat product sources may allow the competent authorities, industry, and other relevant stakeholders to tailor their interventions to control the occurrence of L. monocytogenes in meat products effectively.

Risk-based estimate of effect of foodborne diseases on public health, Greece.

The public health effects of illness caused by foodborne pathogens in Greece during 1996-2006 was quantified by using publicly available surveillance data, hospital statistics, and literature. Results were expressed as the incidence of different disease outcomes and as disability-adjusted life years (DALY), a health indicator combining illness and death estimates into a single metric. It has been estimated that each year ≈370,000 illnesses/million inhabitants are likely caused because of eating contaminated food; 900 of these illnesses are severe and 3 fatal, corresponding to 896 DALY/million inhabitants. Ill-defined intestinal infections accounted for the greatest part of reported cases and 27% of the DALY. Brucellosis, echinococcosis, salmonellosis, and toxoplasmosis were found to be the most common known causes of foodborne illnesses, being responsible for 70% of the DALY. Overall, the DALY metric provided a quantitative perspective on the impact of foodborne illness that may be useful for prioritizing food safety management targets.

Comparing nonsynergy gamma models and interaction models to predict growth of emetic Bacillus cereus for combinations of pH and water activity values.

This research aims to test the absence (gamma hypothesis) or occurrence of synergy between two growth-limiting factors, i.e., pH and water activity (a(w)), using a systematic approach for model selection. In this approach, preset criteria were used to evaluate the performance of models. Such a systematic approach is required to be confident in the correctness of the individual components of the combined (synergy) models. With Bacillus cereus F4810/72 as the test organism, estimated growth boundaries for the a(w)-lowering solutes NaCl, KCl, and glucose were 1.13 M, 1.13 M, and 1.68 M, respectively. The accompanying a(w) values were 0.954, 0.956, and 0.961, respectively, indicating that equal a(w) values result in similar effects on growth. Out of the 12 models evaluated using the preset criteria, the model of J. H. T. Luong (Biotechnol. Bioeng. 27:280-285, 1985) was the best model to describe the effect of a(w) on growth. This a(w) model and the previously selected pH model were combined into a gamma model and into two synergy models. None of the three models was able to describe the combined pH and a(w) conditions sufficiently well to satisfy the preset criteria. The best matches between predicted and experimental data were obtained with the gamma model, followed by the synergy model of Y. Le Marc et al. (Int. J. Food Microbiol. 73:219-237, 2002). No combination of models that was able to predict the impact of both individual and combined hurdles correctly could be found. Consequently, in this case we could not prove the existence of synergy nor falsify the gamma hypothesis.

Comparing nonsynergistic gamma models with interaction models to predict growth of emetic Bacillus cereus when using combinations of pH and individual undissociated acids as growth-limiting factors.

A combination of multiple hurdles to limit microbial growth is frequently applied in foods to achieve an overall level of protection. Quantification of hurdle technology aims at identifying synergistic or multiplicative effects and is still being developed. The gamma hypothesis states that inhibitory environmental factors aiming at limiting microbial growth rates combine in a multiplicative manner rather than synergistically. Its validity was tested here with respect to the use of pH and various concentrations of undissociated acids, i.e., acetic, lactic, propionic, and formic acids, to control growth of Bacillus cereus in brain heart infusion broth. The key growth parameter considered was the maximum specific growth rate, mu(max), as observed by determination of optical density. A variety of models from the literature describing the effects of various pH values and undissociated acid concentrations on mu(max) were fitted to experimental data sets and compared based on a predefined set of selection criteria, and the best models were selected. The cardinal model developed by Rosso (for pH dependency) and the model developed by Luong (for undissociated acid) were found to provide the best fit and were combined in a gamma model with good predictive performance. The introduction of synergy factors into the models was not able to improve the quality of the prediction. On the contrary, inclusion of synergy factors led to an overestimation of the growth boundary, with the inherent possibility of leading to underestimation of the risk under the conditions tested in this research.

Comparison of two optical-density-based methods and a plate count method for estimation of growth parameters of Bacillus cereus.

Quantitative microbiological models predicting proliferation of microorganisms relevant for food safety and/or food stability are useful tools to limit the need for generation of biological data through challenge testing and shelf-life testing. The use of these models requires quick and reliable methods for the generation of growth data and estimation of growth parameters. Growth parameter estimation can be achieved using methods based on plate counting and methods based on measuring the optical density. This research compares the plate count method with two optical density methods, namely, the 2-fold dilution (2FD) method and the relative rate to detection (RRD) method. For model organism Bacillus cereus F4810/72, the plate count method and both optical density methods gave comparable estimates for key growth parameters. Values for the maximum specific growth rate (mu(max)) derived by the 2FD method and by the RRD method were of the same order of magnitude, but some marked differences between the two approaches were apparent. Whereas the 2FD method allowed the derivation of values for lag time (lambda) from the data, this was not possible with the RRD method. However, the RRD method gave many more data points per experiment and also gave more data points close to the growth boundary. This research shows that all three proposed methods can be used for parameter estimation but that the choice of method depends on the objectives of the research.

Applying the food safety objective and related standards to thermal inactivation of Salmonella in poultry meat.

The objective of this study was to investigate the practicality of designing a heat treatment process in a food manufacturing operation for a product governed by a Food Safety Objective (FSO). Salmonella in cooked poultry meat was taken as the working example. Although there is no FSO for this product in current legislation, this may change in the (near) future. Four different process design calculations were explored by means of deterministic and probabilistic approaches to mathematical data handling and modeling. It was found that the probabilistic approach was a more objective, transparent, and quantifiable approach to establish the stringency of food safety management systems. It also allowed the introduction of specific prevalence rates. The key input analyzed in this study was the minimum time required for the heat treatment at a fixed temperature to produce a product that complied with the criterion for product safety, i.e., the FSO. By means of the four alternative process design calculations, the minimum time requirement at 70 degrees C was established and ranged from 0.26 to 0.43 min. This is comparable to the U.S. regulation recommendations and significantly less than that of 2 min at 70 degrees C used, for instance, in the United Kingdom regulation concerning vegetative microorganisms in ready-to-eat foods. However, the objective of this study was not to challenge existing regulations but to provide an illustration of how an FSO established by a competent authority can guide decisions on safe product and process designs in practical operation; it hopefully contributes to the collaborative work between regulators, academia, and industries that need to continue learning and gaining experience from each other in order to translate risk-based concepts such as the FSO into everyday operational practice.

Application of elements of microbiological risk assessment in the food industry via a tiered approach.

Food safety control is a matter for concern for all parts of the food supply chain, including governments that develop food safety policy, food industries that must control potential hazards, and consumers who need to keep to the intended use of the food. In the future, food safety policy may be set using the framework of risk analysis, part of which is the development of (inter)national microbiological risk assessment (MRA) studies. MRA studies increase our understanding of the impact of risk management interventions and of the relationships among subsequent parts of food supply chains with regard to the safety of the food when it reaches the consumer. Application of aspects of MRA in the development of new food concepts has potential benefits for the food industry. A tiered approach to applying MRA can best realize these benefits. The tiered MRA approach involves calculation of microbial fate for a product and process design on the basis of experimental data (e.g., monitoring data on prevalence) and predictive microbiological models. Calculations on new product formulations and novel processing technologies provide improved understanding of microbial fate beyond currently known boundaries, which enables identification of new opportunities in process design. The outcome of the tiered approach focuses on developing benchmarks of potential consumer exposure to hazards associated with new products by comparison with exposure associated with products that are already on the market and have a safe history of use. The tiered prototype is a tool to be used by experienced microbiologists as a basis for advice to product developers and can help to make safety assurance for new food concepts transparent to food inspection services.

Occurrence of Enterobacter sakazakii in food production environments and households.

Enterobacter sakazakii occasionally causes illness in premature babies and neonates. Contamination of infant formulae during factory production or bottle preparation is implicated. Advice to health-care professionals focuses on bottle preparation, but the effectiveness of prevention depends on the degree of contamination and contamination sites, which are generally unknown. To keep contamination to a minimum in the finished product depends on knowledge of the occurrence of E sakazakii. We used a refined isolation and detection method to investigate the presence of this micro-organism in various food factories and households. Environmental samples from eight of nine food factories and from five of 16 households contained E sakazakii. The widespread nature of this micro-organism needs to be taken into account when designing preventive control measures.