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The objective of this study is to compare and assess the effectiveness of real-time polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), and the selective agar plate method for the detection of Salmonella spp. and Listeria monocytogenes in ready-to-eat (RTE) foods. In RTE foods, the detection performance of the three methods (RT-PCR [SureTectTM kit and PowerChekTM kit], LAMP [3M MDS], selective agar) were similar at 0-10, 10-50, 50-100, and 100- CFU/mL of Salmonella spp. and L. monocytogenes. We found that with RT-PCR, the Ct value of salad was significantly higher (p

The recalcitrance of microbial aggregation or biofilm in the food industry underpins the emerging antimicrobial resistance among foodborne pathogens, exacerbating the phenomena of food spoilage, processing and safety management failure, and the prevalence of foodborne illnesses. The challenges of growing tolerance to current chemical and disinfectant-based antibiofilm strategies have driven the urgency in finding a less vulnerable to bacterial resistance, effective alternative antibiofilm agent. To address these issues, various novel strategies are suggested in current days to combat bacterial biofilm. Among the innovative approaches, phytochemicals have already demonstrated their excellent performance in preventing biofilm formation and bactericidal actions against resident bacteria within biofilms. However, the diverse group of phytochemicals and their different modes of action become a barrier to applying them against specific pathogenic biofilm-formers. This phenomenon mandates the need to elucidate the multi-mechanistic actions of phytochemicals to design an effective novel antibiofilm strategy. Therefore, this review critically illustrates the structure - activity relationship, functional sites of actions, and target molecules of diverse phytochemicals regarding multiple major antibiofilm mechanisms and reversal mechanisms of antimicrobial resistance. The implementation of the in-depth knowledge will hopefully aid future studies for developing phytochemical-based next-generation antimicrobials.

This study was conducted to establish effective reduction strategy during the manufacturing process of rice cakes. Simple washing (3 times) and ultrasonic washing (40 kHz, 10 min) were used in the rice washing process, and sodium hypochlorite (100 ppm, 5 min) and chlorine dioxide (20 ppm, 5 min) were used as chemical disinfectants. Combination treatment using ultrasonic washing and the two chemical disinfectants was also performed. The chemical disinfectants were more effective than the ultrasonic cleaning in a single treatment of each method, and sodium hypochlorite showed a greater reduction effect than chlorine dioxide. The combination treatment using both chemical disinfectant and ultrasonic cleaning was found to be more effective than using a single treatment, and no significant difference was observed in the results based on the disinfectant used. During the heating process, which is an important control point of HACCP system, total aerobic bacteria, coliforms, Bacillus cereus and Escherichia coli were inactivated. UV sterilization (30 min, 60 min) was applied as the nonthermal treatment and compared with the general drying method (5, 12 h) during the cooling process of rice cakes. No bacteria were not found after the treatment, whereas the total number of bacteria in the naturally dried rice cakes increased after 12 h, indicating the potential of UV sterilization as an important control point during the cooling process of rice cakes.

Listeria monocytogenes is a foodborne pathogen causing listeriosis, which can be fatal in specific high-risk groups. The aim of this study was to compare the performance (accuracy, sensitivity, and specificity) of 3M™ Molecular Detection System (3M™ MDS) and Korean Food Codex [real-time PCR (RT-PCR) and selective agar] for the detection of L. monocytogenes in various food matrices. The detection performance of the three methods was determined against 100-103 CFU/mL of L. monocytogenes in vitro and showed high accuracy in the order of RT-PCR, 3M™ MDS, and selective agar. There was no difference in sensitivity and specificity of the three methods. Eleven food matrices, selected from agricultural, livestock, and seafood products, were artificially inoculated with 100-103 CFU/25 g of L. monocytogenes and enriched in 3M™ Demi-Fraser Broth. None of the three methods could completely detect low concentrations of L. monocytogenes in a food matrix. However, 3M™ MDS, which is a loop-mediated isothermal amplification (LAMP)-based technology for rapid detection, showed a higher positive detection rate than RT-PCR did, but lower than that of selective agar. These data indicated that 3M™ MDS was superior for the rapid detection of L. monocytogenes, compared to RT-PCR in food matrices containing various inhibitors. Consequentially, the study findings suggest that the LAMP method is a promising alternative to RT-PCR for the rapid detection of foodborne pathogens.

This study aimed to develop a mathematical model for the survival of Clostridium perfringens in hamburgers and sandwiches and to evaluate their microbial risk. The primary model was developed in hamburgers using 4 strains of C. perfringens at 5, 10, 15, 25 and 37 °C, and the kinetic parameters of the primary model were fitted well with the Weibull model (R2 ≥ 0.95). The secondary model was developed and validated in hamburgers and sandwiches using the Davey model, which was evaluated by Bf, Af, and RMSE values within the acceptable range. A probabilistic risk model was developed and simulated using @Risk program to estimate the probability of infection (Pinf) of C. perfringens based on the data on prevalence (n = 100), time, temperature, and consumption of hamburgers and sandwiches (150.00 ± 20.96 g). Based on the simulation model, the mean C. perfringens exposure dose was 0.00976 CFU/g, and the estimated mean Pinf was 1.78 × 10–13, which was very low in comparison with the current available data. The proposed model and the result can thus be useful to establish risk management options and microbial criteria for C. perfringens contamination in hamburgers and sandwiches.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease-19 (COVID-19). More than 143 million cases of COVID-19 have been reported to date, with the global death rate at 2.13%. Currently, there are no licensed therapeutics for controlling SARS-CoV-2 infection. The antiviral effects of heme oxygenase-1 (HO-1), a cytoprotective enzyme that inhibits the inflammatory response and reduces oxidative stress, have been investigated in several viral infections. To confirm whether HO-1 suppresses SARS-CoV-2 infection, we assessed the antiviral activity of hemin, an effective and safe HO-1 inducer, in SARS-CoV-2 infection. We found that treatment with hemin efficiently suppressed SARS-CoV-2 replication (selectivity index: 249.7012). Besides, the transient expression of HO-1 using an expression vector also suppressed the growth of the virus in cells. Free iron and biliverdin, which are metabolic byproducts of heme catalysis by HO-1, also suppressed the viral infection. Additionally, hemin indirectly increased the expression of interferon-stimulated proteins known to restrict SARS-CoV-2 replication. Overall, the findings suggested that HO-1, induced by hemin, effectively suppressed SARS-CoV-2 in vitro. Therefore, HO-1 could be potential therapeutic candidate for COVID-19.

The goal was to identify the biofilm-forming ability of Cronobacter sakazakii on surfaces of stainless steel (SS) and silicone rubber (SR) in contact with infant formula milk. Two representative bacteriophages (PBES04 and PBES19) were used to control the growth of C. sakazakii as well as its biofilm forming ability on either SS or SR surfaces. Bacterial growth was confirmed at 20 °C when PBES04 and PBES19 were used, whereas C. sakazakii was not normally detected in infant formula milk treated with both bacteriophages for 6 h. In an additional biofilm reduction experiment, the biofilm on SS or SR surfaces were reduced by 3.07 and 1.92 log CFU cm-2, respectively after PBES04 treatment, and 3.06 and 2.14 log CFU cm-2, respectively, after PBES19 treatment. These results demonstrate that bacteriophages can be effective in inactivating C. sakazakii in biofilms which could potentially increase food safety in commercial facilities.

The COVID-19 pandemic caused by SARS-CoV-2 has had a major impact on human health and the global economy. Various transmission possibilities of SARS-CoV-2 have been proposed, such as the surface of food in the cold chain and food packaging, as well as the fecal-oral route, although person-to-person contact via droplets and aerosols has been confirmed as the main route of transmission. This study evaluated the survivability of HCoV-229E, a SARS-CoV-2 surrogate, in suspension, on food-contact surfaces and on food at various temperatures, and in simulated digestive fluids by TCID

This study investigated the antimicrobial and antibiofilm efficacy of separate and combined treatments of Lactobacillus curvatus B67-produced postbiotic and the polyphenolic flavanol quercetin against Listeria monocytogenes and Salmonella enterica ser. Typhimurium. The antimicrobial potentiality of the postbiotic was chiefly associated with organic acids (e.g., lactic and acetic acids). At sub-minimum inhibitory concentration (1/2 MIC), the postbiotic and quercetin effectively reduced the pathogenic biofilm cells on processed pork sausage and meat-processing surfaces (e.g., stainless-steel and rubber). Moreover, the postbiotic exhibited strong residual antimicrobial efficacy over diverse pH and temperature ranges. In addition, the combination of postbiotic with quercetin increased the leakage of pathogenic intracellular metabolites (e.g., nucleic acids and protein) and inhibited pathogenic biofilm formation on both biotic and abiotic surfaces. Therefore, this study confirmed that lactic acid bacteria-derived postbiotic and plant-derived quercetin could be used as potential alternative bioprotective agents in the meat processing industry.

Cabbage Kimchi, a traditional Korean fermented food, has occasionally been related to acute gastroenteritis caused by human norovirus (HuNoV). The present study examined the inhibitory effects of electron beam (e-beam) irradiation (1, 3, 5, 7, and 10 kGy) on HuNoV GII.4 in suspension or cabbage Kimchi using reverse transcription quantitative polymerase chain reaction combined with immunomagnetic separation (IMS/RT-qPCR). In addition, physicochemical and sensorial analyses were conducted to assess any change in the quality of cabbage Kimchi following e-beam irradiation. Following e-beam irradiation at 1 to 10 kGy, HuNoV significantly decreased to 0.28 to 2.08 log10 copy number/mL in suspension (P 90% of HuNoV without affecting the quality. PRACTICAL APPLICATION: As the most representative food in Korea, Kimchi needs the sanitation technology that can inhibit viral infection. Our findings suggest that e-beam irradiation can be used to reduce HuNoV effectively in Kimchi without changes in sensorial quality.

The purpose of this research was to characterize Listeria monocytogenes from several environmental and clinical sources and assess the efficacy of single and combined physico-chemical treatments in...

Salmonella is one of the main foodborne pathogens that affect humans and farm animals. The Salmonella genus comprises a group of food-transmitted pathogens which cause highly prevalent foodborne diseases throughout the world. The aim of this study was to appraise the viability of Salmonella Typhimurium biofilm under water treatment at room temperature on different surfaces, specifically stainless steel (SS), plastic (PLA), rubber (RB), and eggshell (ES). After 35 days, the reduction of biofilm on SS, PLA, RB, and ES was 3.35, 3.57, 3.22, and 2.55 log CFU/coupon without water treatment and 4.31, 4.49, 3.50, and 1.49 log CFU/coupon with water treatment, respectively. The dR value (time required to reduce bacterial biofilm by 99% via Weibull modeling) of S. Typhimurium without and with water treatment was the lowest on PLA (176.86 and 112.17 h, respectively) and the highest on ES (485.37 and 2436.52 h, respectively). The viability of the S. Typhimurium on ES and the three food-contact surfaces was monitored for 5 weeks (35days). The results of this study provides valuable information for the control of S. Typhimurium on different surfaces in the food industry, which could reduce the risk to consumers.

The contamination of seafood with Vibrio species can have severe repercussions in the seafood industry. Vibrio species can form mature biofilms and persist on the surface of several seafoods such as crabs, oysters, mussels, and shrimp, for extended duration. Several conventional approaches have been employed to inhibit the growth of planktonic cells and prevent the formation of Vibrio biofilms. Since Vibrio biofilms are mostly resistant to these control measures, novel alternative methods need to be urgently developed. In this review, we propose environmentally friendly approaches to suppress Vibrio biofilm formation using a hypothesized mechanism of action.

Understanding the microbial community of cheese is important in the dairy industry, as the microbiota contributes to the safety, quality, and physicochemical and sensory properties of cheese. In this study, the microbial compositions of different cheeses (Cheddar, provolone, and Swiss cheese) and cheese locations (core, rind, and mixed) collected from the Arbuthnot Dairy Center at Oregon State University were analyzed using 16S rRNA gene amplicon sequencing with the Illumina MiSeq platform (Illumina, San Diego, CA). A total of 225 operational taxonomic units were identified from the 4,675,187 sequencing reads generated. Streptococcus was observed to be the most abundant organism in provolone (72 to 85%) and Swiss (60 to 67%), whereas Lactococcus spp. were found to dominate Cheddar cheese (27 to 76%). Species richness varied significantly by cheese. According to alpha diversity analysis, porter-soaked Cheddar cheese exhibited the highest microbial richness, whereas smoked provolone cheese showed the lowest. Rind regions of each cheese changed color through smoking and soaking for the beverage process. In addition, the microbial diversity of the rind region was higher than the core region because smoking and soaking processes directly contacted the rind region of each cheese. The microbial communities of the samples clustered by cheese, indicated that, within a given type of cheese, microbial compositions were very similar. Moreover, 34 operational taxonomic units were identified as biomarkers for different types of cheese through the linear discriminant analysis effect size method. Last, both carbohydrate and AA metabolites comprised more than 40% of the total functional annotated genes from 9 varieties of cheese samples. This study provides insight into the microbial composition of different types of cheese, as well as various locations within a cheese, which is applicable to its safety and sensory quality.

Background Food can readily be tainted by pathogenic microorganisms, turning it into a stigmatized poison with potential harm to the consumer. To date, 31 identified and countless unidentified pathogens have been reported as accountable for foodborne illness globally. Approximately 66% of illnesses originate solely from pathogenic bacteria, and the association of these microorganisms in mono- and mixed-biofilms may increase bacterial intoxication and infection-linked problems in humans. Scope and approach Bacterial species live in close proximity to each other, share matrix components, and build three-dimensional rigid biofilm structures in nature. Due to their strong phenotypic heterogeneity and natural resistance to common sanitizers and disinfectants, mono- and mixed-bacterial biofilms can remain in food and on the surfaces of food processing appliances after sanitizing treatment. Green synthesis of “eco-friendly” anti-biofilm agents has become the necessary response to the occurrence of mono- and mixed-bacterial biofilms, in order to avoid the negative effects of conventional chemical and physical approaches on human health and the environment. Key findings and conclusions Advanced research has already proved the potential and efficacy of several microbe-derived anti-biofilm agents. This current review investigates the concerns associated with both mono- and mixed-bacterial biofilms and their control by biological anti-biofilm agents in different food industries. Moreover, this review highlights the recent achievements, existing limitations, and possible technical suggestions for further development of broad-spectrum microbe-derived anti-biofilm agents for the food industry.

In this study, the effect of three essential oils (EOs) – clove oil (CO), thyme oil (TO), and garlic oil (GO), which are generally recognized as safe – on the planktonic growth, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), motility, biofilm formation, and quorum sensing (QS) of Vibrio parahaemolyticus was investigated. All three EOs showed bacteriostatic activity, with MICs in the range 0.02%–0.09% (v/v). CO and TO completely controlled planktonic growth at 0.28% and 0.08% (v/v), which is four times their MIC (4 × MIC), after 10 min, whereas GO completely controlled growth at 0.36% (v/v) (4 × MIC) after treatment for 20 min. V. parahaemolyticus motility was significantly reduced by all three EOs at 4 × MIC (0.28% for CO, 0.08% for TO, and 0.36% for GO), whereas QS was controlled and biofilm formation reduced by all three EOs at 8 × MIC (0.56% for CO, 0.16% for TO, and 0.72% for GO) after 30 min of treatment. These results suggest that CO, TO, and GO have a significant inhibitory effect on V. parahaemolyticus cells in biofilm sand thus represent a promising strategy for improving food safety. These results provide the evidence required to encourage further research into the practical use of the proposed EOs in food preparation processes.

The purpose of this study was to conduct a risk assessment for Clostridium perfringens foodborne illness via kimchi consumption in South Korea. Prevalence of C. perfringens in kimchi, kimchi consumption amount and frequency, and distribution conditions (time and temperature) from manufacture to the home were determined. C. perfringens initial contamination level was estimated using Beta distribution [Beta (6, 79)]. Potential C. perfringens cell counts during distribution were predicted using the Weibull model (primary models, R2 = 0.923–0.953) and a polynomial model [(δ = 1/(0.2385 + (− 0.0307 × Temp) + (0.0011 × Temp2)), R2 = 0.719]. Average daily consumption data was assessed using Gamma distribution [1.0444, 91.767, RiskShift (0.16895), RiskTruncate (0, 1078)]. The mean risk of C. perfringens-associated foodborne illness following kimchi consumption was found to be 1.21 × 10−17. These results suggest that the risk of C. perfringens foodborne illness from kimchi consumption, under current conditions, can be considered to be very low in S. Korea.

Chicken breast meat is considered as the main source of Salmonella infection in humans. The aim of this study was to isolate lytic bacteriophages specific for Salmonella enterica serovars Enteritidis and examine their efficacy in a cocktail for the biocontrol of Salmonella spp. in raw chicken breast meat. Four lytic phages belonging to the Myoviridae and Siphoviridae families were isolated from a river proximate to a duck farm. They exhibited broad lytic activities against 11 strains of S. Enteritidis, 11 strains of S. Typhimurium, and one each of S. Paratyphi A, S. San Diego, and S. Typhi. The phages were determined to be stable, exhibited similar degrees of resistance to heat and pH, and had latent periods ranging from 5 to 30 min. In addition, the phage particles were 100% adsorbed within 18 to 40 min. Viable cell counts of bacteria were significantly reduced in raw chicken breast samples (P < 0.05) when treated with a cocktail of all four bacteriophages at 4 °C for 7 days (multiplicities of infection were from 104 to 106 ). These results indicate the potential efficacy of the bacteriophage cocktail as a biological agent against S. Enteritidis in raw chicken breast meat. PRACTICAL APPLICATION: Our findings demonstrate that the phages could be effective in reducing the viability of Salmonella spp. bacteria in chicken breast meat. Therefore, the phage cocktail is a potential bactericidal agent for the biocontrol of Salmonella spp. in raw chicken breast meat and could be used use in various poultry industries in the future.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 269 million people and killed more than 5.3 million people worldwide. Although fomite transmission of SARS-CoV-2 has been continuously reported, few studies have been conducted on food contact surfaces. Therefore, this study aimed to investigate the viability of coronaviruses on food contact surfaces and to remove SARS-CoV-2 contaminated on food contact surfaces with disinfectants. At 20 °C, SARS-CoV-2 was inactivated within 48 h on all food contact surfaces. At 4 °C, it was inactivated at 48 h on kraft paper and 96 h on parchment paper, but it was viable up to 5 days in low-density polyethylene (LDPE). At -20 °C, SARS-CoV-2 did not decrease by even 1 log on all food contact surfaces until 5 days. Treatment with 70% ethanol or 1000 ppm sodium hypochlorite for 5 min was sufficient to completely remove SARS-CoV-2 from 6 food contact surfaces. Similarly, UV-C irradiation at 60 mJ/cm

In the aquatic environment, microorganisms are predominantly organized as biofilms. Biofilms are formed by the aggregation of microbial cells and are surrounded by a matrix of extracellular polymeric substances (EPS) secreted by the microbial cells. Biofilms are attached to various surfaces, such as the living tissues, indwelling medical devices, and piping of the industrial potable water system. Biofilms formed from a single species has been extensively studied. However, there is an increased research focus on multispecies biofilms in recent years. It is important to assess the microbial mechanisms underlying the regulation of multispecies biofilm formation to determine the drinking water microbial composition. These mechanisms contribute to the predominance of the best-adapted species in an aquatic environment. This review focuses on the interactions in the multispecies biofilms, such as coaggregation, co-metabolism, cross-species protection, jamming of quorum sensing, lateral gene transfer, synergism, and antagonism. Further, this review explores the dynamics and the factors favoring biofilm formation and pathogen transmission within the drinking water distribution systems. The understanding of the physiology and biodiversity of microbial species in the biofilm may aid in the development of novel biofilm control and drinking water disinfection processes.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the cause of the COVID-19 outbreaks, is transmitted by respiratory droplets and has become a life-threatening viral pandemic worldwide. The aim of this study was to evaluate the effects of different chemical (chlorine dioxide [ClO

Foodborne pathogen-mediated biofilms in food processing environments are severe threats to human lives. In the interest of human and environmental safety, natural substances with antimicrobial properties and generally regarded as safe (GRAS) status are the futuristic disinfectants of the food industry. In this study, the efficacy of bioactive, soluble products (metabolic by-products) from lactic acid bacteria (LAB) and plant-derived essential oils (EO) were investigated as biocidal agents. The postbiotic produced by kimchi-derived Leuconostoc mesenteroides J.27 isolate was analyzed for its metabolic components to reveal its antimicrobial potential against three pathogenic microorganisms (Vibrio parahaemolyticus, Pseudomonas aeruginosa, and Escherichia coli). Additionally, the efficacy of food-grade EO (eugenol and thymol, respectively) was also assessed in our study. Determination of the minimum inhibitory concentration (MIC) of postbiotic and EO against three tested pathogens revealed that the sub-MIC (0.5 MIC) of postbiotic and EO could efficiently inhibit the biofilm formation on both seafood (squid) and seafood-processing surfaces (rubber and low-density polyethylene plastic). Moreover, the polymerase chain reaction (PCR) analysis confirmed that the LAB J.27 isolate possesses bacteriocin- and enzyme-coding genes. The residual antibacterial activity of the produced postbiotic was maintained over a diverse pH range (pH 1-6) but was entirely abolished at neutral or higher pH values. However, the activity was unaffected by exposure to high temperatures (100 and 121 °C) and storage (30 days). Notably, the leakage of intracellular metabolites, damage to DNA, and the down-regulation of biofilm-associated gene expression in the pathogens increased significantly (p 0.05) following the combination treatment of postbiotic with thymol compared to postbiotic with eugenol. Nonetheless, all in vitro results indicated the prospective use of combining Leu. mesenteroides J.27-derived postbiotic with both EO as a "green preservative" in the seafood industry to inhibit the formation of pathogenic microbial biofilms.

Microbial communities on soil are fundamental for the long-term sustainability of agriculture ecosystems. Microbiota in soil would impact the yield and quality of blueberries since microbial communities in soil can interact with the rhizosphere of plant. This study was conducted to determine how different mulching treatments induce changes in soil microbial composition, diversity, and functional properties. A total of 150 soil samples were collected from 5 different mulch treatments (sawdust, green weed mat, sawdust topped with green weed mat, black weed mat, and sawdust topped with black weed mat) at 3 different depths (bottom, middle, and top region of 20 cm soil depth) from 2 different months (June and July 2018). A total of 8,583,839 sequencing reads and 480 operational taxonomic units (OTUs) of bacteria were identified at genus level. Eight different plant growth promoting rhizobacteria (PGPR) were detected, and the relative abundances of Bradyrhizobium, Bacillus, and Paenibacillus were more than 0.1% among all soil samples. Sampling depth and month of soil samples impacted the amount of PGPR, while there were no significant differences based on mulch type. Functional properties of bacteria were identified through PICRUSt2, which found that there is no significant difference between mulch treatment, depth, and month. The results indicated that sampling month and depth of soil impacted the relative abundance of PGPR in soil samples, but there were no significant differences of functional properties and beneficial microbial communities based on mulch type.

Biofilm is an advanced form of protection that allows bacterial cells to withstand adverse environmental conditions. The complex structure of biofilm results from genetic-related mechanisms besides other factors such as bacterial morphology or substratum properties. Inhibition of biofilm formation of harmful bacteria (spoilage and pathogenic bacteria) is a critical task in the food industry because of the enhanced resistance of biofilm bacteria to stress, such as cleaning and disinfection methods traditionally used in food processing plants, and the increased food safety risks threatening consumer health caused by recurrent contamination and rapid deterioration of food by biofilm cells. Therefore, it is urgent to find methods and strategies for effectively combating bacterial biofilm formation and eradicating mature biofilms. Innovative and promising approaches to control bacteria and their biofilms are emerging. These new approaches range from methods based on natural ingredients to the use of nanoparticles. This literature review aims to describe the efficacy of these strategies and provide an overview of recent promising biofilm control technologies in the food processing sector.

The purpose of this study was to investigate sublethal concentrations (SLC) of bactericidal antibiotics (ampicillin, gentamicin, kanamycin, and vancomycin) on the mutation frequency and stress response of antibiotic-induced-mutated (AIM) Listeria monocytogenes. Three L. monocytogenes strains (reference, clinical, and food isolate strains) were used in this study. SLC of bactericidal antibiotics significantly increased the mutation frequency in L. monocytogenes. It was found that AIM L. monocytogenes had a superior biofilm-forming ability than nontreated L. monocytogenes. This result correlated with the amounts of EPS produced (polysaccharide and protein) in the early stage of biofilm formation. AIM L. monocytogenes showed strong viability under food-associated stress (thermal, osmotic, and acidic) compared to nontreated L. monocytogenes. In addition, expression levels of motility (flaA) and virulence genes (hlyA, actA, and prfA) of AIM L. monocytogenes were significantly downregulated in the reference strain but significantly upregulated or similar to the expression levels in the clinical and food isolate strains compared to nontreated L. monocytogenes. Based on our results, SLC of bactericidal antibiotics increased the mutation frequency in L. monocytogenes, facilitated the adaptation of the bacterium to food-associated stress, and led to an increase in its pathogenicity.

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.

This study developed predictive growth models of Salmonella enterica Serovar Typhimurium on lettuce washed with chlorine (100~300 ppm) and ultrasound (US, 37 kHz, 380 W) treatment and stored at different temperatures (10~25°C) using a polynomial equation. The primary model of specific growth rate (SGR) and lag time (LT) showed a good fit (R2≥0.92) with a Gompertz equation. A secondary model was obtained using a quadratic polynomial equation. The appropriateness of the secondary SGR and LT model was verified by coefficient of determination (R2=0.98~0.99 for internal validation, 0.97~0.98 for external validation), mean square error (MSE=- 0.0071~0.0057 for internal validation, -0.0118~0.0176 for external validation), bias factor (Bf=0.9918~1.0066 for internal validation, 0.9865~1.0205 for external validation), and accuracy factor (Af=0.9935~1.0082 for internal validation, 0.9799~1.0137 for external validation). The newly developed models for S. Typhimurium could be incorporated into a tertiary modeling program to predict the growth of S. Typhimurium as a function of combined chlorine and US during the storage. These new models may also be useful to predict potential S. Typhimurium growth on lettuce, which is important for food safety purposes during the overall supply chain of lettuce from farm to table. Finally, the models may offer reliable and useful information of growth kinetics for the quantification microbial risk assessment of S. Typhimurium on washed lettuce.

Aspergillus flavus is the potential pathogenic mold in red pepper powder ( Capsicum annuum L.) and gochujang (red pepper paste), which can produce mycotoxins. This study investigated the effects of gamma ray, e-beam, and X-ray irradiation on the reduction of A. flavus on red pepper powder and gochujang and physicochemical and sensory quality changes. Gamma ray and e-beam at 3.5 kGy reduced A. flavus effectively (>4 log), without deteriorating the physicochemical quality. Same dose of X-ray did not cause any deterioration of the physicochemical quality. However, reduction effect of A. flavus in red pepper powder and gochujang by 3.5 kGy X-ray was under 2 log. Further, sensory quality analysis showed no significant difference in color, appearance, texture, and overall acceptability after three irradiations. However, flavor changes of red pepper powder and gochujang after three irradiations were mentioned by panelists. In this study, gamma ray and e-beam irradiation were effective in eliminating A. flavus present in red pepper powder and gochujang, but X-ray irradiation was not effective. The results indicate gamma ray and e-beam are effective in controlling microorganisms present in powdery or paste foods, but the X-ray was not effective.

This study developed predictive growth models of Aeromonas hydrophila on lettuce as a function of combined storage temperature (15–35°C) and relative humidity (RH, 60–80%) using a polynomi...

Bivalve molluscan shellfish, such as oysters, clams, and cockles, are well-recognized as vectors that concentrate foodborne pathogens by filter feeding. The objective of this study was to investigate the distribution and persistence of hepatitis A virus (HAV) in experimentally contaminated oysters that were either fed or not fed with algae. Oysters were experimentally contaminated with HAV and maintained in depuration conditions. qRT-PCR, immunohistochemistry (IHC), and in situ hybridization (ISH) were performed on oyster samples collected at 0, 1, 3, 5, and 7 days post-inoculation. When HAV-contaminated oysters were depurated for 7 days, HAV was detected in 91.1–97.8% of the digestive glands and gills. While the high viral load in the digestive glands in oysters did not change significantly regardless of algae-feeding, the viral load of the gills gradually decreased in both groups during the depuration. HAV antigen and RNA were detected in the digestive diverticula and connective tissues by both IHC and ISH. HAV was detected in the stomach, intestine, and gills by only ISH. The distribution of HAV in various oyster tissues may explain the persistence of contamination in oysters during the depuration process.

This study investigated the synergistic effects of combined chlorine (200, 500, 700, and 1000 ppm) and vitamin B1 (1000, 2000, and 3000 ppm) on the murine norovirus-1 (MNV-1), a human norovirus (NoV) surrogate, on oyster surface. Vitamin B1 slightly reduced MNV-1 (0.04–0.3 log-reduction), whereas chlorine significantly reduced MNV-1 (0.4–1.0 log-reduction). The combined chlorine and vitamin B1 resulted in a 0.52–1.97 log-reduction of MNV-1. The synergistic reduction in the MNV titer was not dependent on the concentrations of chlorine and vitamin B1, and it ranged between 0.08 and 1.03 log10 PFU/mL. The largest synergistic reduction observed was for the combined 700 ppm chlorine and 1000 ppm vitamin B1. The pH and mechanical texture of the oysters were not significantly changed by the combined 0–1000 ppm chlorine and 3000 ppm vitamin B1. The overall sensory acceptability were significantly (P

This study was conducted to evaluate antilisterial activity in deli-style turkey using one of the inhibitors: hop α- or β-acids at 5 ppm, potassium acetate/potassium diacetate (PAPD) at 0.5%, their combinations, potassium lactate/sodium diacetate (PLSD) at 2.5% for positive control, and ethanol at 5 ppm for negative control. Deli-style turkey was formulated and manufactured traditionally. To simulate Listeria contamination in processing plants, the deli turkey was sliced in24 h of production, inoculated with Listeria monocytogenes (2 to 3 log CFU/g), and vacuum-stored at 4 or 7°C for 60 d. To simulate Listeria contamination in grocery stores, the deli turkey was vacuum-stored for 30 and 60 d prior to slicing, inoculation, and aerobic storage at 4 or 7°C for 10 d. Physicochemical properties of the deli turkey were not significantly different among treatments (P0.05). Addition of hop acids at 5 ppm did not inhibit Listeria in deli meat during 60 d of vacuum-storage at 4 or 7°C, whereas organic acids and hop acids/PAPD significantly inhibited Listeria (P0.05), with the best inhibition observed for hop β-acids/PAPD at 7°C/60 d. During 10 d of aerobic storage at 4°C, hop acid/PAPD, PLSD, or PAPD showed listeristatic effects, whereas hop acids alone allowed Listeria to grow by 0.9 CFU/g. During 10 d of aerobic storage at 7°C, hop acid/PAPD, PLSD, and PAPD significantly reduced Listeria populations than hop α-acids, β-acids, and no-inhibitor control (P0.05). These results indicated the combination of hop β-acids/PAPD provides more effective inhibition than any single addition of hop acids and PLSD (P0.05) at 7°C/60 d in vacuum storage, with intermediate inhibition observed for PAPD and α-acids/PAPD.