Simulating Cross-Contamination of Cooked Pork with Salmonella enterica from Raw Pork through Home Kitchen Preparation in Vietnam

Phenotypic and Genotypic Characterization of Escherichia coli and Salmonella spp. Isolates from Pigs at Slaughterhouse and from Commercial Pork Meat in Portugal

Background: Foodborne diseases are a serious public health concern, and food-producing animals are a major source of contamination. Methods: The present study analysed Escherichia coli and Salmonella spp. isolated from faecal samples of 100 fattening pigs and from 52 samples of pork meat. Results: The results showed that the majority of the analysed meat samples were considered satisfactory in terms of microbiological quality (92.3% for E. coli and 94.2% for Salmonella spp.). Salmonella spp. was identified in 5.8% of the meat samples, whereas E. coli was detected in 89.5% of all samples (69.2% in meat and 100% in faecal samples). Furthermore, 1.9% of the faecal samples contained Shiga-toxin-producing E. coli and 3.9% contained enterotoxigenic E. coli. All sequenced isolates presented virulence genes for extraintestinal pathogenic E. coli. Moreover, 75.0% of E. coli isolates from meat and 71.8% from faeces samples showed antibiotic resistance, with 40.7% and 51.4%, respectively, being multidrug-resistant (MDR). The most prevalent resistances were to tetracycline, ampicillin, and sulfamethoxazole, and one E. coli isolate showed resistance to extended-spectrum β-lactamase. Conclusions: This study highlights the role of pigs as a potential source of human contamination and the importance of a One Health approach to ensure food safety and to promote public health.

Food Safety Practices of Food Handlers in China and their Correlation with Self-reported Foodborne Illness

Food service facilities are important sites where foodborne diseases have been reported to occur frequently. This study aims to determine the correlation between self-reported foodborne diseases and food-safety practices followed by food handlers of various food service facilities. A cross-sectional survey was conducted from March 1, 2022 to December 30, 2022 in Wuhu City, Anhui Province, China. Data were collected through face-to-face interviews and having the selected food handlers fill in a self-compiled questionnaire. Of the 1072 food handlers included in the study, 88 (8.2%) reported having experienced symptoms of foodborne diseases in the past 4 weeks. The following food-safety practices correlated with self-reported foodborne diseases: (1) infrequently using 3-compartment sinks to separately clean different types of raw food materials (P < 0.05, OR = 2.312); (2) infrequently removing non-edible parts of aquatic products outside a specific room for food processing (P < 0.001, OR = 3.916); (3) infrequently immediately refrigerating cold dishes prepared in advance to be consumed later (P < 0.001, OR = 4.048); (4) often store perishable foods at 8-60°C in the indoor environment after cooking and before eating (P < 0.05, OR = 2.068); (5) infrequently reheating cooked perishable food stored at 8-60°C for more than 2 h before eating (P < 0.05, OR = 1.934); and (6) often storing raw and cooked food in the same container (P < 0.001, OR = 3.818). Hence, a better supervision of food-safety practices of catering workers may reduce the frequency of foodborne-disease outbreaks in food service facilities.

Effect of light-touch intervention and associated factors to microbial contamination at small-scale pig slaughterhouses and traditional pork shops in Vietnam

Traditional pork value chains dominate the production and distribution of pork in Vietnam; however, the high level of microbiological contamination in pork may increase the risk of food-borne disease for consumers. There is limited evidence about how to feasibly and scalably reduce microbial contamination in pork sold in traditional markets. This study aimed to assess the effectiveness of light-touch interventions for changing worker behaviour in small-scale slaughterhouses and vendors at traditional pork shops, as well as to identify risk factors for pork contamination. The intervention packages consisted of providing hygiene tools and delivering a food safety training which had been designed in a participatory way and covered 10 small-scale slaughterhouses and 29 pork shops. Pig carcasses, retailed pork, contact surfaces, and hands were sampled to measure the total bacterial count (TBC) and Salmonella contamination before, three and six weeks after the intervention, and trainee practices were observed at the same time. Linear and generalized linear mixed effects models were constructed to identify risk factors for TBC and Salmonella contamination at the slaughterhouses and pork shops. The interventions at slaughterhouses and pork shops both showed a slight reduction of TBC contamination in pig carcasses and Salmonella prevalence in retailed pork, while the TBC in retailed pork decreased only marginally. For slaughterhouses, the regression model indicated that smoking or eating during slaughtering (indicating poor hygienic practices) was associated with TBC increasing, while cleaning floors and wearing boots reduced TBC contamination. For pork shops, using rough materials (cardboard or wood) to display pork was the only factor increasing TBC contamination in pork, whereas cleaning knives was associated with lower TBC. Besides, the presence of supporters and wearing aprons reduced the probability of Salmonella contamination in pork. The findings highlight the effectiveness of light-touch interventions in reducing microbial contamination in pig carcasses at small-scale slaughterhouses and pork at traditional shops over the study period.

Modeling the Temperature Effect on the Growth of Uropathogenic Escherichia coli in Sous-Vide Chicken Breast

Uropathogenic Escherichia coli (UPEC) is known to cause 65-75% of human urinary tract infection (UTI) cases. Poultry meat is a reservoir of UPEC, which is suspected to cause foodborne UTIs. In the present study, we aimed to determine the growth potential of UPEC in ready-to-eat chicken breasts prepared by sous-vide processing. Four reference strains isolated from the urine of UTI patients (Bioresource Collection and Research Center [BCRC] 10,675, 15,480, 15,483, and 17,383) were tested by polymerase chain reaction assay for related genes to identify their phylogenetic type and UPEC specificity. A cocktail of these UPEC strains was inoculated into sous-vide cooked chicken breast at 103-4 colony-forming unit (CFU)/g and stored at 4°C, 10°C, 15°C, 20°C, 30°C, and 40°C. Changes in the populations of UPEC during storage were analyzed by a one-step kinetic analysis method using the U.S. Department of Agriculture [USDA] Integrated Pathogen Modeling Program-Global Fit [IPMP-Global Fit]. The results showed that the combination of the no lag phase primary model and the Huang square-root secondary model fitted well with the growth curves to obtain the appropriate kinetic parameters. This combination for predicting UPEC growth kinetics was further validated using it to study additional growth curves at 25°C and 37°C, which showed that the root mean square error, bias factor, and accuracy factor were 0.49-0.59 (log CFU/g), 0.941-0.984, and 1.056-1.063, respectively. In conclusion, the models developed in this study are acceptable and can be used to predict the growth of UPEC in sous-vide chicken breast.

Identification of risk profiles for Salmonella prevalence in pig supply chains in South Korea using meta-analysis and a quantitative microbial risk assessment model

International travel and the globalization of food supplies have increased the risk of epidemic foodborne infections. Salmonella strains, particularly non-typhoidal Salmonella (NTS), are major zoonotic pathogens responsible for gastrointestinal diseases worldwide. In this study, the prevalence and Salmonella contamination in pigs/carcasses throughout the South Korean pig supply chain and the associated risk factors were evaluated using Systematic reviews and meta-analyses (SRMA), and quantitative microbial risk assessment (QMRA). The prevalence of Salmonella in finishing pigs, which is one of the major starting inputs of the QMRA model was calculated through SRMA of studies conducted in south Korea in order to complement and enhance the robustness of the model. Our findings revealed that the pooled Salmonella prevalence in pigs was 4.15% with a 95% confidence interval (CI) of 2.56 to 6.66%. Considering the pig supply chain, the highest prevalence was detected in slaughterhouses (6.27% [95% CI: 3.36; 11.37]), followed by farms (4.16% [95% CI: 2.32; 7.35]) and meat stores (1.21% [95% CI: 0.42; 3.46]). The QMRA model predicted a 3.9% likelihood of Salmonella-free carcasses and a 96.1% probability of Salmonella-positive carcasses at the end of slaughter, with an average Salmonella concentration of 6.38 log CFU/carcass (95% CI: 5.17; 7.28). This corresponds to an average contamination of 1.23 log CFU/g (95% CI: 0.37; 2.48) of pork meat. Across the pig supply chain, the highest Salmonella contamination was predicted after transport and lairage, with an average concentration of 8 log CFU/pig (95% CI: 7.15; 8.42). Sensitivity analysis indicated that Salmonella fecal shedding (r = 0.68) and Salmonella prevalence in finishing pigs (r = 0.39) at pre-harvest were the most significant factors associated with Salmonella contamination in pork carcasses. Although disinfection and sanitation interventions along the slaughter line can reduce contamination levels to some extent, effective measures should be taken to reduce Salmonella prevalence at the farm level to improve the safety of pork consumption.

A glance into traditional pig slaughtering practices in Vietnam and opportunities for zoonotic disease prevention

Introduction

African swine fever in Vietnam is contributing to existing concerns over zoonotic disease transmission from sick pigs to humans. While slaughterhouses are key sites of occupational hazards to workers and contamination of meat, the specific slaughtering practices contributing to zoonotic occupational and foodborne disease risks remain under-researched. Our objective is to identify and characterize aspects of pig slaughtering processes that contribute to such risks.

Methods

We draw on qualitative observations, photos, and videos from three mobile slaughterhouses and seven abattoirs in Hung Yen, Vietnam.

Results

Based on our analysis, areas likely leading to zoonotic disease risks include slaughtering procedures, personal hygiene of workers, equipment sanitation, and facility sanitation. Within the small-scale swine industry, slaughtering practices are long-standing and difficult to change.

Conclusion

Our study underscores the importance of hygiene training of workers, improvements to equipment and facilities, and awareness-building activities targeting consumers to reduce the burden of zoonotic disease risks in small-scale pig slaughter settings.

Quantitative risk assessment of salmonellosis in Cambodian consumers through chicken and pork salad consumption

Salmonella is a globally important foodborne bacterial pathogen that poses a high risk to human health. This study aimed to estimate the risk to Cambodian consumers from acquiring salmonellosis after consuming chicken and pork salad, using a quantitative microbial risk assessment (QMRA). Chicken and pork salads are typical Cambodian dishes containing raw vegetables and boiled chicken meat or pork. As previously described, chicken meat and pork samples (n = 204 of each) were collected from traditional markets in 25 Cambodian provinces to generate data on Salmonella contamination. Salad preparation and consumption practices were surveyed in 93 Cambodian households and this information was used to design an experiment to assess Salmonella cross-contamination from raw meat to ready-to-eat salad. In the part of the study reported here, data on consumption, Salmonella in salad, dose-response, and predicted salmonellosis were modeled using Monte Carlo simulations at 10,000 iterations. The prevalence of Salmonella in chicken meat and pork were set to 42.6 and 45.1%, respectively, with average most probable number (MPN) per gram of Salmonella in chicken meat was 10.6 and in pork 11.1 MPN/g, based on an earlier study. Half of the interviewed households cooked meat for the salad directly after purchase. The QMRA model showed that the modeled annual risk of salmonellosis from consuming chicken salad, pork salad and both chicken and pork salad were 11.1% probability of illness per person per year (90% CI 0.0–35.1), 4.0% (90% CI 0.0–21.3), and 14.5% (90% CI 0.0–33.5), respectively. The factors most influencing the estimate were cross-contamination while preparing the salad, followed by the prevalence of Salmonella in chicken meat and pork at the market. The wide confidence interval for the incidence was mainly due to the variability in reducing bacteria concentration by cooking and salad consumption. The predicted risk of salmonellosis due to chicken and pork salad consumption is high, and the study provides evidence supporting control measures of improving the safety of retailed chicken and pork obtained from markets to households and improving food preparation methods in the household.

Experimental cross-contamination of chicken salad with Salmonella enterica serovars Typhimurium and London during food preparation in Cambodian households

Non-typhoidal Salmonellae are common foodborne pathogens that can cause gastroenteritis and other illnesses in people. This is the first study to assess the transfer of Salmonella enterica from raw chicken carcasses to ready-to-eat chicken salad in Cambodia. Twelve focus group discussions in four Cambodian provinces collected information on typical household ways of preparing salad. The results informed four laboratory experiments that mimicked household practices, using chicken carcasses inoculated with Salmonella. We developed four scenarios encompassing the range of practices, varying by order of washing (chicken or vegetables first) and change of chopping utensils (same utensils or different). Even though raw carcasses were washed twice, Salmonella was isolated from 32 out of 36 chicken samples (88.9%, 95% CI: 73.0–96.4) and two out of 18 vegetable samples (11.1%, 95% CI: 1.9–36.1). Salmonella was detected on cutting boards (66.7%), knives (50.0%) and hands (22.2%) after one wash; cross-contamination was significantly higher on cutting boards than on knives or hands (p-value < 0.05). The ready-to-eat chicken salad was contaminated in scenario 1 (wash vegetables first, use same utensils), 2 (wash vegetables first, use different utensils) and 3 (wash chicken first, use same utensils) but not 4 (wash chicken first, use different utensils) (77.8%, 11.1%, 22.2% and 0%, respectively). There was significantly higher Salmonella cross-contamination in scenario 1 (wash vegetables first, use same utensils) than in the other three scenarios. These results show how different hygiene practices influence the risk of pathogens contaminating chicken salad. This information could decrease the risk of foodborne disease in Cambodia and provides inputs to a quantitative risk assessment model.

Effects of environmental conditions (temperature, pH, and glucose) on biofilm formation of Salmonella enterica serotype Kentucky and virulence gene expression

Salmonella is a foodborne pathogen and an emerging zoonotic bacterial threat in the food industry. The aim of this study was to evaluate the biofilm formation by a cocktail culture of 3 wild isolates of Salmonella enterica serotype Kentucky on plastic (PLA), silicon rubber (SR), and chicken skin surfaces under various temperatures (4, 10, 25, 37, and 42°C) and pH values (4.0, 5.0, 6.0, 7.0, and 8.0). Then, at the optimum temperature and pH, the effects of supplementation with glucose (0, 0.025, 0.05, and 0.4% w/v) on biofilm formation were assessed on each of the surfaces. The results indicated that higher temperatures (25 to 42°C) and pH values (7.0 and 8.0) led to more robust biofilm formation than lower temperatures (4 and 10°C) and lower pH levels (4.0 to 6.0). Moreover, biofilm formation was induced by 0.025% glucose during incubation at the optimum temperature (37°C) and pH (7.0) but inhibited by 0.4% glucose. Consistent with this finding, virulence related gene (rpoS, rpoH, hilA, and avrA) expression was increased at 0.025% glucose and significantly reduced at 0.4% glucose. This results also confirmed by field emission scanning electron microscope, confocal laser scanning microscopy, and autoinducer-2 determination. This study concluded that optimum environmental conditions (temperature 37°C, pH 7.0, and 0.25% glucose) exhibited strong biofilm formation on food and food contract surfaces as well as increased the virulence gene expression levels, indicating that these environmental conditions might be threating conditions for food safety.

Prevalence of Salmonella spp. and Staphylococcus aureus in Chicken Meat and Pork from Cambodian Markets

Salmonella spp. and Staphylococcus aureus are two of the most common foodborne bacteria in animal-source foods (ASF) that cause illness worldwide. This study aimed to determine the prevalence of Salmonella spp. and S. aureus in chicken meat and pork in markets in Cambodia. Sampling was done in 52 traditional markets and 6 supermarkets in 25 provinces of Cambodia between October 2018 and August 2019. In total, 532 samples were obtained: chicken meat and pork (n = 408, 204 of each), chicken and pork cutting board swabs (n = 124, 62 of each). All samples were analyzed for the presence of Salmonella spp. and S. aureus; colony-forming units per gram (CFU/g) of coagulase-positive Staphylococci (CPS) were counted, and a subset of samples was also analyzed for the most probable number (MPN, n = 136) of Salmonella. The overall prevalence of Salmonella spp. and S. aureus were 42.1% (224/532) and 29.1% (155/532), respectively, with 14.7% (78/532) of samples containing both bacteria. The prevalence of Salmonella spp. in chicken meat was 42.6%, on chicken cutting board it was 41.9%, on pork it was 45.1%, and the pork cutting board 30.6%. Chicken meat had a significantly (p-value < 0.05) higher prevalence of S. aureus, 38.2%, compared to the chicken cutting board, 17.7%, pork 28.9%, and pork cutting board 11.3%. Mean MPN-Salmonella was 10.6 MPN/g in chicken and 11.1 MPN/g in pork samples. Average Log CFU/g of CPS in chicken and pork samples were 2.6 and 2.5, respectively. The results indicate that chicken meat and pork in Cambodia were highly contaminated with Salmonella spp. and S. aureus, posing risks to consumers' health. Urgent interventions are necessary to improve hygiene for safer meat in Cambodian markets.

Quantification of Cross-Contamination of Campylobacter jejuni during Food Preparation in a Model Kitchen in China

ABSTRACT

Numerous outbreak investigations and case-control studies of campylobacteriosis have provided evidence that handling Campylobacter-contaminated chicken products is a high risk factor for infection and illness. In this study, the cross-contamination and transfer rates of Campylobacter jejuni from chicken to ready-to-eat food were determined in various food handling scenarios. Skinless raw chicken breasts were artificially contaminated with C. jejuni and diced on cutting boards of three different materials. Whether cold water, cold water with detergent, or hot water was used, statistically significant differences were found between the transfer rates of C. jejuni to unwashed and washed cutting boards or hands, respectively. When both kitchen knife and cutting board were reused after dicing the artificially contaminated chicken, the transfer rates of C. jejuni to cucumber cut on bamboo, wooden, and plastic cutting boards were 16.28, 12.82, and 5.32%, respectively. The transfer rates from chicken to bread, a large lift-up water faucet handle, and a small twist faucet handle via unwashed hands were 0.49, 4.64, and 3.14%, respectively. This research provides scientific evidence that various types of contaminated kitchenware and cook's hands are vital potential vehicles for the cross-contamination of Campylobacter from raw chicken to ready-to-eat food and emphasizes the importance of timely and proper cleaning to prevent cross-contamination during food handling; therefore, high-quality consumer education to reduce the risk of foodborne infection is urgent and necessary.

HIGHLIGHTS

Food safety practices of food handlers at home engaged in online food businesses during COVID-19 pandemic in the Philippines

This study was conducted to assess the self-reported and observed food safety practices (FSP) of food handlers, who deliver food products that are prepared and cooked at home during the COVID-19 pandemic in the Philippines. 751 participated in the online survey who were selected using criterion sampling. A questionnaire developed by the researcher was used to gather data with Cronbach Alpha of 0.91. t-test, ANOVA, and Fleiss kappa were performed to treat data. There were no significant differences between self-reported FSP in four dimensions and demographic characteristics, except for age, where a significant difference exists between the FSP of the four age groups along food preparation (F ​= ​4.530,ρ<0.01). The FSP in the four dimensions obtained a weighted x¯ and σ of 1.72 ​± ​0.69 which is interpreted as Sometimes Practiced. The food handlers at home inadequately and inappropriately practiced the protocols in keeping the food safe to eat. The observed reports showed that the food handlers at home do not meet food safety standards as indicated in the weighted x¯ and σ in the four dimensions 1.63 ± 0.11, with a description of Sometimes Practiced. Observed practices further show very poor adherence to guidelines. Test for inter-rater reliability yielded almost perfect agreement (κ ​= ​0.81, ρ<0.05). There exists a significant difference with the FSP in personal hygiene (t ​= ​0.964, ρ<0.05), cross-contamination prevention and sanitation (t ​= ​0.815, ρ<0.05), food preparation (t ​= ​0.753, ρ<0.05), and food delivery (t ​= ​0.794, ρ<0.05). Government and non-government agencies should work together towards educating the food handlers at home on effective ways to learn about food safety concepts so they could become advocates of safer food practices.

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Online food business is growing due to restrictions brought about by the pandemic.

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Self-reported FSP of food handlers reveal compliance to food safety standards.

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Food handlers violate food safety protocols based on expert observations.

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There is significant difference between the self-reported and the observed FSP.

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Food safety training involving food handlers in online businesses is imperative.

Multidrug Resistance and Virulence Profiles of Salmonella Isolated from Swine Lymph Nodes

Salmonella spp. is a foodborne pathogen present in the pork production chain, leading to potential contamination of end products and causing salmonellosis cases and outbreaks worldwide. The emergence of multidrug-resistant (MDR) Salmonella spp., especially isolates obtained from animal origin food, is a global concern. This study aimed to isolate Salmonella from swine mesenteric lymph nodes (MLN) and to characterize the virulence and antibiotic resistance profiles. MLN samples were obtained from a swine slaughterhouse and subjected to Salmonella spp. isolation. Ten MLN samples were positive and 29 isolates were identified based on PCR (invA and ompC) and serotyping: Derby, Cerro, and Give. Pulsed-field gel electrophoresis allowed to group the isolates based on their serotypes, resulting in three major clusters. All isolates presented the virulence-related genes pefA, sipA, sopB, spaN, and pagC. Relatively high numbers of Salmonella spp. were resistant to neomycin, polymyxin B, ciprofloxacin, tetracycline, and nalidixic acid. Furthermore, 25 isolates presented simultaneous resistance to three or more antibiotic classes, being characterized as MDR. The obtained results confirmed the relevance of swine as reservoirs of Salmonella spp. in the pork production chain and demonstrated the MDR profiles of isolates. Proper control and surveillance are required to avoid the contamination of end products.

Control of pathogens in fresh pork sausage by inclusion of Lactobacillus sakei BAS0117

A pork sausage was produced with low sodium content (1.64%) to which Lactobacillus sakei was added with the aim of developing a meat pork sausage for cooking and having technological, organoleptic, and hygienic advantages. The lactic acid bacteria (LAB) L. sakei, Lactococcus sp., and Pediococcus pentosaceus were submitted to extreme pH, temperature, and NaCl conditions. Lactobacillus sakei was used in pork sausage because of its resistance to different culture conditions and its antimicrobial potential. The food-borne pathogens Listeria monocytogenes Scott A, Enterococcus faecalis, and Staphylococcus aureus were used as indicator microorganisms to evaluate the antimicrobial activity of selected LAB strains. Salmonella enterica serotype Choleraesuis is a common pathogen of pigs. To the raw sausage product containing L. sakei and nonpathogenic endogenous microbiota, we added about >10⁴ and <10⁵ CFU/g of S. enterica serotype Choleraesuis to evaluate the inhibitory potential of L. sakei towards this pathogen. Salmonella Choleraesuis was inhibited in the presence of L. sakei over 7 days of storage of the meat product (about 3.0 log cycles reduction). Lactobacillus sakei significantly increased inhibition when compared with the nonfermented sausage. Thus, L. sakei BAS0117 played an important role as an additional hurdle in the fermented meat pork sausage during storage.

Relationship of Sanitation Parameters with Microbial Diversity and Load in Raw Meat from the Outlets of the Metropolitan City Biratnagar, Nepal

The main aim of this study is to assess the microbial load of raw meat from outlets of Biratnagar and its relationship with several sanitation parameters. Samples were taken from meat outlets, and required microbiological procedures were followed as per guidelines. Approximately 63.6% of microbes were present in meat with poor sanitation while 36.4% were present in meat with good sanitation. Fungal contamination in poorly kept mutton was one and half times greater than chicken/mutton of good sanitation. Fungi such as Penicillium (21.3%), Mucor (16.3%), Aspergillus (15%), and Trichosporon (13.8%) were most predominant. 73.8% of meat samples contained Staphylococcus spp., 61.3% contained E. coli, 48.8% of Pseudomonas spp., and 37.5% samples contained Salmonella spp. Outlets selling both types of meat showed no significant difference in microbial types. Mean of TVC of meat is 8.2 log CFU/g. Mean TVC of mutton (7.6 log CFU/g) is lower than mean TVC of chicken/meat (8.5 log CFU/g) and differed significantly. Tiled outlets showed comparatively lower bacterial contamination than cemented outlets which was statistically significant (t = -3.16, p=0.002). With the difference among microbial type and few sanitation parameters being statistically significant, it can be suggested that outlets should be tiled (p=0.002), showcased (p=0.001), and the meat-handling employee must wear washed apron (p=0.013). Proper cleaning of water supply and use area (p ≤ 0.001) and drainage (p=0.048) maintain a good meat sanitation (p ≤ 0.001) which reduces microbial contamination significantly. To diminish microbiological load on meat sold in the Biratnagar city, standard operating methods should be practiced.