Recent advances on the formation, detection, resistance mechanism, and control technology of Listeria monocytogenes biofilm in food industry.

Listeria monocytogenes is an important foodborne pathogen that causes listeriosis, a severe and fatal condition. Biofilms are communities of microorganisms nested within a self-secreted extracellular polymeric substance, and they protect L. monocytogenes from environmental stresses. Biofilms, once formed, can lead to the persistence of L. monocytogenes in processing equipment and are therefore considered to be a major concern for the food industry. This paper briefly introduces the recent advancements on biofilm formation characteristics and detection methods, and focuses on analysis of the mechanism of L. monocytogenes biofilm resistance; Moreover, this paper also summarizes and discusses the existing different techniques of L. monocytogenes biofilm control according to the physical, chemical, biological, and combined strategies, to provide a theoretical reference to aid the choice of effective control technology in the food industry.

Prevalence, antibiotic resistance and molecular characterization of Staphylococcus aureus in ready-to-eat fruits and vegetables in Shanghai, China.

Staphylococcus aureus (S. aureus) is one of the foodborne pathogens. This study aimed to investigate the prevalence of S. aureus in ready-to-eat (RTE) fruits and vegetables in Shanghai, China. We evaluated antibiotic resistance patterns and genetic diversity of isolates through whole genome sequencing. Our findings demonstrated that out of 143 market samples, 47 (32.87%) tested positive for S. aureus, with the prevalence rates ranging from 10% to 57.14% among 12 types of RTE fruits and vegetables. Most isolates were resistant to trimethoprim-sulphamethoxazole, oxacillin, and ampicillin. We identified a total of 15 antibiotic resistance genes associated with resistance to 6 antibiotics, such as fosfomycin, fluoroquinolone, and ß-lactam. Adhesion genes and enterotoxin genes, including icaA, icaB, icaC, set, seg, and sec, were also identified. Seven multi-locus sequence types (MLST) were detected, two of which were novel (ST7208 and ST7986). Notably, ST705-t529 (34.04%) and ST6-t701 (27.79%) represented the predominant types of S. aureus. Furthermore, three of the isolates were confirmed to be methicillin-resistant S. aureus by mecA genes. Taken together, our results highlight the high prevalence of S. aureus in RTE fruits and vegetables, posing a potential threat to food safety, particularly due to its high level of antibiotic resistance.

Effect of Temperature, pH, and aw on Cereulide Synthesis and Regulator Genes Transcription with Respect to Bacillus cereus Growth and Cereulide Production.

Bacillus cereus is a food-borne pathogen that can produce cereulide in the growth period, which causes food poisoning symptoms. Due to its resistance to heat, extreme pH, and proteolytic enzymes, cereulide poses a serious threat to food safety. Temperature, pH, and aw can influence cereulide production, but there is still a lack of research with multi-environmental impacts. In this study, the effects of temperature (15~45 °C), pH (5~8), and aw (0.945~0.996) on the emetic reference strain B. cereus F4810/72 growth, cereulide production, relevant ces genes (cesA, cesB, cesP), and transcription regulators genes (codY and abrB) expression at transcription level were studied. B. cereus survived for 4~53 h or grew to 6.85~8.15 log10 CFU/mL in environmental combinations. Cereulide accumulation was higher in mid-temperature, acidic, or high aw environments. Increased temperature resulted in a lower cereulide concentration at pH 8 or aw of 0.970. The lowest cereulide concentration was found at pH 6.5 with an increased aw from 0.970 to 0.996. Water activity had a strong effect on transcriptional regulator genes as well as the cesB gene, and temperature was the main effect factor of cesP gene expression. Moreover, environmental factors also impact cereulide synthesis at transcriptional levels thereby altering the cereulide concentrations. The interaction of environmental factors may result in the survival of B. cereus without growth for a period. Gene expression is affected by environmental factors, and temperature and pH may be the main factors influencing the correlation between B. cereus growth and cereulide formation. This study contributed to an initial understanding of the intrinsic link between the impact of environmental factors and cereulide formation and provided valuable information for clarifying the mechanism of cereulide synthesis in combined environmental conditions.

Exposure of Salmonella enterica serovar 1,4,[5],12:i:- to benzalkonium chloride leads to acquired resistance to this disinfectant and antibiotics.

AIMS: Disinfectants such as benzalkonium chloride (BC), extensively used in animal farms and food-processing industries, contribute to the development of adaptive and cross-resistance in foodborne pathogens, posing a serious threat to food safety and human health. The purpose of this study is to explore whether continuous exposure of Salmonella enterica serovar 1,4,[5],12:i:- (S. 1,4,[5],12:i:-) to sublethal concentrations of BC could result in acquired resistance to this agent and other environmental stresses (e.g. antibiotics, heat, and acid). METHODS AND RESULTS: BC tolerance increased in all tested strains after exposure to gradually increasing concentrations of BC, with increases in minimum inhibitory concentrations between two and sixfold. The survival rate of BC-adapted strains was significantly (P < 0.05) higher than that of their wild-type (non-adapted) counterparts in lethal concentrations of BC. In addition, significant reductions (P < 0.05) in zeta potential were observed in BC-adapted strains compared to wild-type ones, indicating that a reduction in cell surface charge was a cause of adaptative resistance. More importantly, two BC-adapted strains exhibited increased antibiotic resistance to levofloxacin, ceftazidime, and tigecycline, while gene mutations (gyrA, parC) and antibiotic efflux-related genes (acrB, mdsA, mdsB) were detected by genomic sequencing analysis. Moreover, the tolerance of BC-adapted strains to heat (50, 55, and 60°C) and acid (pH 2.0, 2.5) was strain-dependent and condition-dependent. CONCLUSIONS: Repeated exposure to sublethal concentrations of BC could result in the emergence of BC- and antibiotic-resistant S. 1,4,[5],12:i:- strains.

Different cellular fatty acid pattern and gene expression of planktonic and biofilm state Listeria monocytogenes under nutritional stress.

Listeria monocytogenes is a Gram-positive bacterium frequently involved in food-borne disease outbreaks and is widely distributed in the food-processing environment. This work aims to depict the impact of nutrition deficiency on the survival strategy of L. monocytogenes both in planktonic and biofilm states. In the present study, cell characteristics (autoaggression, hydrophobicity and motility), membrane fatty acid composition of MRL300083 (Lm83) in the forms of planktonic and biofilm-associated cells cultured in TSB-YE and 10-fold dilutions of TSB-YE (DTSB-YE) were investigated. Additionally, the relative expression of related genes were also determined by RT-qPCR. It was observed that cell growth in different bacterial life modes under nutritional stress rendered the cells a distinct phenotype. The higher autoaggression (AAG) and motility of the planktonic cells in DTSB-YE is associated with better biofilm formation. An increased proportion of unsaturated fatty acid/saturated fatty acid (USFA/SFA) indicates more fluidic biophysical properties for cell membranes of L. monocytogenes in planktonic and biofilm cells in DTSB-YE. Biofilm cells produced a higher percentage of USFA and straight fatty acids than the corresponding planktonic cells. An appropriate degree of membrane fluidity is crucial for survival, and alteration of membrane lipids is an essential adaptive response. The adaptation of bacteria to stress is a multifactorial cellular process, the expression of flagella-related genes fliG, fliP, flgE and the two-component chemotactic system cheA/Y genes of planktonic cells in DTSB-YE significantly increased compared to that in TSB-YE (p < 0.05). This study provides new information on the role of the physiological adaptation and gene expression of L. monocytogenes for planktonic and biofilm growth under nutritional stress.

Distribution-based maximum likelihood estimation methods are preferred for estimating Salmonella concentration in chicken when contamination data are highly left-censored.

Salmonella is a common chicken-borne pathogen that causes human infections. Data below the detection limit, referred to as left-censored data, are frequently encountered in the detection of pathogens. The approach of handling the censored data was regarded to affect the estimation accuracy of microbial concentration. In this study, a set of Salmonella contamination data was collected from chilled chicken samples using the most probable number (MPN) method, which consisted of 90.42% (217/240) non-detect values. Two simulated datasets with fixed censoring degrees of 73.60% and 90.00% were generated based on the real-sampling Salmonella dataset for comparison. Three methodologies were applied for handling left-censored data: (i) substitution with different alternatives, (ii) the distribution-based maximum likelihood estimation (MLE) method, and (iii) the multiple imputation (MI) method. For each dataset, the negative binomial (NB) distribution-based MLE and zero-modified NB distribution-based MLE were preferable for highly censored data and resulted in the least root mean square error (RMSE). Replacing the censored data with half the limit of quantification was the next best method. The mean concentration of Salmonella monitoring data estimated by the NB-MLE and zero-modified NB-MLE methods was 0.68 MPN/g. This study provided an available statistical method for handling bacterial highly left-censored data.

Cereulide and Emetic Bacillus cereus: Characterizations, Impacts and Public Precautions.

Cereulide, which can be produced by Bacillus cereus, is strongly associated with emetic-type food poisoning outbreaks. It is an extremely stable emetic toxin, which is unlikely to be inactivated by food processing. Considering the high toxicity of cereulide, its related hazards raise public concerns. A better understanding of the impact of B. cereus and cereulide is urgently needed to prevent contamination and toxin production, thereby protecting public health. Over the last decade, a wide range of research has been conducted regarding B. cereus and cereulide. Despite this, summarized information highlighting precautions at the public level involving the food industry, consumers and regulators is lacking. Therefore, the aim of the current review is to summarize the available data describing the characterizations and impacts of emetic B. cereus and cereulide; based on this information, precautions at the public level are proposed.

A review of potential antibacterial activities of nisin against Listeria monocytogenes: the combined use of nisin shows more advantages than single use.

Listeria monocytogenes is a foodborne pathogen causing serious public health problems. Nisin is a natural antimicrobial agent produced by Lactococcus lactis and widely used in the food industry. However, the anti-L. monocytogenes efficiency of nisin might be decreased due to natural or acquired resistance of L. monocytogenes to nisin, or complexity of the food environment. The limitation of nisin as a bacteriostatic agent in food could be improved using a combination of methods. In this review, the physiochemical characteristics, species, bioengineered mutants, and antimicrobial mechanism of nisin are reviewed. Strategies of nisin combined with other antibacterial methods, including physical, chemical, and natural substances, and nanotechnology to enhance antibacterial effect are highlighted and discussed. Additionally, the antibacterial efficiency of nisin applied in real meat, dairy, and aquatic products is evaluated and analyzed. Among the various binding treatments, the combination with natural substances is more effective than the combination with physical and chemical methods. However, the combination of nisin and nanotechnology has more potential in terms of the impact on food quality.

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.

Potential antimicrobial activities of probiotics and their derivatives against Listeria monocytogenes in food field: A review.

Listeria monocytogenes is an important food-borne pathogen, which could be detected in food, environmental and clinical samples. It contaminates food in any of the stages during production, processing, and storage, resulting in potential food safety issues. Traditional physical and chemical methods are effective in inhibiting the growth of L. monocytogenes and extending the shelf life of foods, however, the application of these methods usually results in undesirable damage to food quality. Recently, biological-based antimicrobial methods have attracted numerous attention due to their promising antimicrobial effects and ability to maintain food quality. The application of probiotics, as one of the biological based antimicrobial methods, has been widely reported that could effectively inhibit the growth of L. monocytogenes. In this review, human listeriosis and the current contamination situation of L. monocytogenes in foods are summarized first. Then, the effects of probiotics on the growth, biofilm formation, and virulence of L. monocytogenes in foods are discussed. Furthermore, the inhibitory mechanisms of the probiotics and their metabolites against L. monocytogenes are highlighted. With a comprehensive understanding of the bacteriostatic effect of the probiotics, the latest applications of probiotics in dairy products, meat products, and fresh products are presented and discussed.

Detecting the Mechanism of Action of Antimicrobial Peptides by Using Microscopic Detection Techniques.

Increasing antibiotic resistance has shifted researchers' focus to antimicrobial peptides (AMPs) as alternatives to antibiotics. AMPs are small, positively charged, amphipathic peptides with secondary helical structures. They have the ability to disrupt the bacterial membrane and create wedges due to electrostatic differences. Water molecules enter the pathogens through those wedges and disrupt their normal cellular functioning, eventually causing the death of the pathogens. Keeping in mind the importance of AMPs, this review compiles recent data and is divided into three parts. The first part explains the AMP structure and properties, the second part comprises the spectroscopy techniques currently used for evaluating the AMP-bacterial targeting mechanism as well as its structure and safety; and the third part describes the production of AMPs from an animal source (whey protein). Most of the peptides that were used in recent studies have been either the precursors of a natural peptide or synthetic peptides with some modifications, but data on the exploitation of dairy protein are scarce. Among the little-studied milk proteins and peptides, in the last three years, whey protein has been studied the least based on the reported data. Because whey protein is a leftover part of cheese making that often drains out as cheese waste, causing soil and environmental pollution, today, the need of the hour is to produce safe AMPs from whey protein. The use of whey protein that is based on hydrolyzing lactic acid bacteria with some structural modifications can increase AMPs' potency, stability, and safety, and it can also help to avoid soil and environmental pollution as a result of whey drainage.

Climatic suitability projection for deciduous fruit tree cultivation in main producing regions of northern China under climate warming.

China is the largest fruit producer and consumer market in the world. Understanding the growing conditions responses to climate change is the key to predict future site suitability of main cultivation areas for certain deciduous fruit trees. In this study, we used dynamic and growing degree day models driven by downscaled daily temperatures from 22 global climate models to project the effects of climate change on growing conditions for deciduous fruit trees under two representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios over 2 future time periods (represented by central years 2050s and 2085s) in northern China. The results showed a general increase of available winter chill for all sites under RCP4.5 scenario, and the most dramatic increase in chill accumulation could reach up to 36.8% in northeast regions for RCP8.5. However, the forecasted chill will decrease by 6.4% in southeast stations under RCP8.5 by 2085s. Additionally, the increase rate of growing season heat showed spatially consistency, and the most pronounced increase was found in the RCP8.5 by 2085s. For the southwest station, median heat accumulation increased by 20.8% in the 2050s and 37.1% in the 2085s under RCP8.5. Similar increasing range could be found in the northeast station; the median growing season heat increased by 19.8% and 38.8% in the 2050s and 2085s under RCP8.5, respectively. Moreover, the date of last spring frost was expected to advance and the frequency of frost occurrences was projected to decline in the study area compared to the past. Overall, the present study improves understanding regarding site-specific characteristics of climatic suitability for deciduous fruit tree cultivation in main producing regions of northern China. The results could provide growers and decision-makers with theoretical evidence to take adaptive measure to ensure fruit production in future.

[Placenta-specific virulence factors involved in Listeria monocytogenes infection].

Listeria monocytogenes (LM) is a food-borne pathogen that can cause listeriosis. Pregnant women are main target population of listeriosis due to pregnancy-associated immune deficiency and unique intracellular infection ability of LM to non-phagocytic cells. LM can cross the placental barrier and cause significant harm to the fetus, including premature birth, miscarriage and even stillbirth. The role of placenta-specific virulence factors is particularly important for researchers to understand how it crosses the placental barrier and infects the fetus during LM infection. This review started by describing the listeriosis in pregnant women, followed by summarizing the advances in understanding the LM vertical transplacental infection and the mechanism of LM colonization in the placenta. Finally, recent advances in identifying placenta-specific virulence factors involved in LM infections were presented, with the aim to facilitate the control of LM transplacental infection and the improvement of food safety.

Modelling the Adhesion and Biofilm Formation Boundary of Listeria monocytogenes ST9.

Listeria monocytogenes is a major foodborne pathogen that can adhere to or form a biofilm on food contact surfaces, depending on the environmental conditions. The purpose of this work is to determine the adhesion and biofilm formation boundaries for L. monocytogenes ST9 under the combination environments of temperature (5, 15, and 25 °C), NaCl concentration (0%, 3%, 6%, and 9% (w/v)) and pH (5.0, 6.0, 7.0, and 8.0). The probability models of adhesion and biofilm formation were built using the logistic regression. For adhesion, only the terms of linear T and NaCl are significant for L. monocytogenes ST9 (p < 0.05), whereas the terms of linear T, NaCl, and pH, and the interaction between T and pH were significant for biofilm formation (p < 0.05). By analyzing contour maps and their surface plots for two different states, we discovered that high temperature promoted adhesion and biofilm formation, whereas excessive NaCl concentration inhibited both of them. With a stringent threshold of 0.1667, the accuracy rate for identifying both adhesion/no-adhesion and biofilm formation/no-biofilm formation events were 0.929, indicating that the probability models are reasonably accurate in predicting the adhesion and biofilm formation boundary of L. monocytogenes ST9. The boundary model may provide a useful way for determining and further controlling L. monocytogenes adhesion and biofilm formation in various food processing environments.

Antibiotic Resistance of Salmonella Typhimurium Monophasic Variant 1,4,[5],12:i:-in China: A Systematic Review and Meta-Analysis.

Antibiotic resistance in Salmonella is a global public health problem. Salmonella enterica serovar 1,4,[5],12:i:- (S. 1,4,[5],12:i:-), a monophasic variant of Salmonella Typhmurium, is one of the leading Salmonella serovars in several countries. This study aimed to assess the prevalence of antibiotic resistance to this serovar in China through a systematic review and meta-analysis. Nineteen eligible studies during 2011-2021 were included. A total of 4514 isolates from humans, animals, foods, and the environment were reported, which mainly concerned isolates found in Guangdong, Guangxi, Jiangsu, and Shanghai. A random-effects model was used to estimate the pooled resistance rate of S. 1,4,[5],12:i:-. Rates were found to be very high (values ≥ 75%) for tetracycline, ampicillin, sulfisoxazole, and streptomycin; high (50-75%) for nalidixic acid, amoxicillin-clavulanic acid, and chloramphenicol; and moderate (25-50%) for trimethoprim-sulfamethoxazole, kanamycin, trimethoprim, and gentamicin. The rates of resistance to ciprofloxacin, cefotaxime, ceftriaxone, cefepime, ceftazidime, and colistin were low (values ≤ 25%), but of great concern in terms of their current clinical importance. Furthermore, a high multidrug resistance rate (86%, 95% CI: 78-92%) was present in S. 1,4,[5],12:i:-, with the ASSuT pattern largely dominating. Subgroup analysis results showed that the high heterogeneity of resistance rates was not entirely dependent on isolated sources. Taken together, the severity of antibiotic resistance in S. 1,4,[5],12:i:- urgently requires the rational use of antibiotics in future infection control and antibiotic stewardship programs.

Lactiplantibacillus plantarum subsp. plantarum and Fructooligosaccharides Combination Inhibits the Growth, Adhesion, Invasion, and Virulence of Listeria monocytogenes.

Listeria monocytogenes is a foodborne pathogen responsible for many food outbreaks worldwide. This study aimed to investigate the single and combined effect of fructooligosaccharides (FOS) and Lactiplantibacillus plantarum subsp. plantarum CICC 6257 (L. plantarum) on the growth, adhesion, invasion, and virulence of gene expressions of Listeria monocytogenes 19112 serotype 4b (L. monocytogenes). Results showed that L. plantarum combined with 2% and 4% (w/v) FOS significantly (p < 0.05) inhibited the growth of L. monocytogenes (3-3.5 log10 CFU/mL reduction) at the incubation temperature of 10 °C and 25 °C. Under the same combination condition, the invasion rates of L. monocytogenes to Caco-2 and BeWo cells were reduced more than 90% compared to the result of the untreated group. After L. plantarum was combined with the 2% and 4% (w/v) FOS treatment, the gene expression of actin-based motility, sigma factor, internalin A, internalin B, positive regulatory factor A, and listeriolysin O significantly (p < 0.05) were reduced over 91%, 77%, 92%, 89%, 79%, and 79% compared to the result of the untreated group, respectively. The inhibition level of the L. plantarum and FOS combination against L. monocytogenes was higher than that of FOS or L. plantarum alone. Overall, these results indicated that the L. plantarum and FOS combination might be an effective formula against L. monocytogenes.

Heat shock in Cronobacter sakazakii induces direct protection and cross-protection against simulated gastric fluid stress.

The bacterial heat shock response in foodborne pathogens is caused by exposure to higher temperatures which poses a great threat to food safety because it can undermine food processing interventions and host defense. The study assessed the heat and acid resistance of Cronobacter sakazakii following heat shock (53 °C for 15min). Inactivation curves of the heat-shocked and non-shocked C. sakazakii cells at four temperatures (56, 58, 60, and 62 °C) and simulated gastric fluid (SGF, pH 3.0) were examined and fitted with the log-linear model and the Weibull model. The inactivation parameters obtained on the basis of the Weibull model showed that heat shock significantly (p < 0.05) increased the values of δ (time to reach 1 log reduction) and t3d (time to reach 3 log reduction) under thermal and acid inactivation. The results proved that heat shock provided C. sakazakii direct protection from a more adverse heat challenge and cross-protection from SGF, i.e. there was a heat shock response. Results of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that seven protein species showed enhanced expression, while four protein species showed decreased expression in the heat-shocked compared to the non-heat-shocked C. sakazakii cells. Quantitative real-time reverse transcriptase PCR (RT-qPCR) revealed upregulation of six stress related genes, ibpA, ibpB (both encoding molecular chaperons), Hsp15 (encoding heat shock protein), Hsp20 (encoding small heat-shock protein), HspQ (encoding proteases) and rpoS (encoding stationary phase sigma factor), following heat shock treatment. In addition, heat shock induced an increase proportion of saturated fatty acids (SFA), cyclic fatty acids (CFA) and the ratio of saturated fatty acids to unsaturated fatty acids (SFA/USFA), whereas reducing the proportion of unsaturated fatty acids (USFA). Consequently, establishment of inactivation models of C. sakazakii could provide data support for quantitative microbial risk assessment (QMRA). Exploration of enhanced resistance mechanisms might provide clues for prevention and control of contamination by heat-shocked C. sakazakii.

A Meta-Analysis and Systematic Review of Listeria monocytogenes Response to Sanitizer Treatments.

Listeria monocytogenes is a ubiquitous organism that can be found in food-related environments, and sanitizers commonly prevent and control it. The aim of this study is to perform a meta-analysis of L. monocytogenes response to sanitizer treatments. According to the principle of systematic review, we extracted 896 records on the mean log-reduction of L. monocytogenes from 84 publications as the dataset for this study. We applied a mixed-effects model to describe L. monocytogenes response to sanitizer treatment by considering sanitizer type, matrix type, biofilm status, sanitizer concentration, treatment time, and temperature. Based on the established model, we compared the response of L. monocytogenes under different hypothetical conditions using forest plots. The results showed that environmental factors (i.e., sanitizer concentration, temperature, and treatment time) affected the average log-reduction of L. monocytogenes (p < 0.05). L. monocytogenes generally exhibited strong resistance to citric acid and sodium hypochlorite but had low resistance to electrolyzed water. The planktonic cells of L. monocytogenes were less resistant to peracetic acid and sodium hypochlorite than the adherent and biofilm cells. Additionally, the physical and chemical properties of the contaminated or inoculated matrix or surface also influenced the sanitizer effectiveness. This review may contribute to increasing our knowledge of L. monocytogenes resistance to sanitizers and raising awareness of appropriate safety precautions.

The Prevalence and Epidemiology of Salmonella in Retail Raw Poultry Meat in China: A Systematic Review and Meta-Analysis.

Foodborne disease caused by Salmonella is an important public health concern worldwide. Animal-based food, especially poultry meat, is the main source of human salmonellosis. The objective of this study was to evaluate the prevalence and epidemiology of Salmonella contamination in raw poultry meat commercialized in China. Following the principle of systematic review, 98 sets of prevalence data were extracted from 74 publications conducted in 21 Chinese provincial regions. The random-effect model was constructed for subgrouping analysis by meat category, preservation type, and geographical location. The prevalence levels differed from high to low among raw poultry meat, including chicken, 26.4% (95% CI: 22.4-30.8%); pigeon, 22.6% (95% CI: 18.2-27.8%); duck, 10.1% (95% CI: 5.3-18.2%); and other poultry meat, 15.4% (95% CI: 12.0-19.5%). Prevalence data on the preservation type revealed that chilled poultry meat might be more likely to experience cross-contamination than non-chilled poultry meat in China. The distribution map of Salmonella for raw poultry meat showed that a higher prevalence level was found in the Shaanxi, Henan, Sichuan, and Beijing regions. All subgroups possessed high amounts of heterogeneity (I2 > 75%). The scientific data regarding the differences in prevalence levels between meat category, preservation method, and geographical region sources might be useful to improve specific interventions to effectively control the incidence of Salmonella in poultry meat.

[Preliminary quantitative risk assessment of the effect of Salmonella on human health in retail fresh pork].

OBJECTIVE: A quantitative microbiological risk assessment was conducted for Salmonella spp. in fresh pork from retail stores to consumers in China in order to provide evidence for adopting effective risk management measures. METHODS: The national food safety and risk monitoring data was used to estimate the initial contamination level of Salmonella in the retail fresh pork. The growth model and the cross-contamination model of Salmonella were referenced from the ComBase data base and scientific literature, respectively. Then the human health risk was predicted by the consumption of Salmonella-contaminated fresh pork and the Beta-Poisson dose-response model. RESULTS: The number of Salmonellosis per year among 1 million residents due to fresh pork was estimated to be 4748.The sensitivity analysis showed that the risk of Salmonellosis was mainly and positively correlated with the preparation rate of ready to eat food, the consumption quantity of pork, the initial contamination level of Salmonella in fresh pork, and the proportion of improper cleaning of knives and chopping boards. When the contamination level of Salmonella in fresh pork is controlled below 1 CFU/g, the average probability of illness will be reduced by 59.39%; the average probability of illness will be reduced by 58.97% by increasing the ratio of complete cleaning of chopping boards or the separation ratio of chopping boards for raw and ready-to-eat food to 90%. CONCLUSION: The risk could be effectively reduced by controlling the concentration of Salmonella contamination in retail pork or improving hygiene practices.