Akkermansia muciniphila Prevents Fatty Liver Disease, Decreases Serum Triglycerides, and Maintains Gut Homeostasis.

The objective of this study was to elucidate the effect of intestinal Akkermansia muciniphila bacteria on fatty liver disease. Five-week-old C57BL/6N mice were administered either phosphate-buffered saline (PBS; control) or A. muciniphila at 108 to 109 CFU/ml, and were fed either a 45% fat diet (high-fat diet [HFD]) or a 10% fat diet (normal diet [ND]) for 10 weeks. After 10 weeks, the mice were euthanized, and blood and tissue samples, including adipose tissue, cecum, liver, and brain, were immediately collected. Biochemical and histological analyses were conducted, and the expression levels of related factors were compared to determine the antiobesity effects of Akkermansia muciniphila The gut microbiome was analyzed in fecal samples. Oral administration of A. muciniphila significantly (P < 0.05) lowered serum triglyceride (TG) and alanine aminotransferase (ALT) levels in obese mice. Compared to the non-A. muciniphila-treated group, the expression of SREBP (regulator of TG synthesis in liver tissue) was decreased in the A. muciniphila-treated group. The expression of IL-6 in the liver of obese mice was decreased following the administration of A. muciniphila Furthermore, alterations in the ratio of Firmicutes to Bacteroidetes and the decrease in bacterial diversity caused by the HFD were restored upon the administration of A. muciniphila These results indicate that A. muciniphila prevents fatty liver disease in obese mice by regulating TG synthesis in the liver and maintaining gut homeostasis.IMPORTANCE This study investigated the effect of Akkermansia muciniphila on fatty liver disease. Although some research about the effects of A. muciniphila on host health has been published, study of the relationship between A. muciniphila administration and fatty liver, as well as changes in the gut microbiota, has not been conducted. In this study, we demonstrated that A. muciniphila prevented fatty liver disease by regulation of the expression of genes that regulate fat synthesis and inflammation in the liver.

The role of Pseudomonas aeruginosa DesB in pathogen-host interaction.

Pseudomonas aeruginosa, commonly found in environments, can cause chronic lung disease in immunocompromised patients. In previous study, an aerobic desaturase (DesB) in P. aeruginosa exerted considerable effects on virulence factor production. The objective of this study was to analyze the role of DesB on the virulence traits of P. aeruginosa in the host. For the in vitro experiments, cells and supernatants from wild-type (WT) P. aeruginosa and its desB mutant were collected. The diluted cells were added to the A549 cell monolayer in order to determine cell viability, invasion ability, and/or immune response. For the in vivo experiments, 6-week-old ICR mice were infected with 6-7 log CFU bacterial cells using endotracheal intubation. The ratio of lung weight to body weight and survival rate of each bacterial strain in the lung were measured. The histopathology of lung tissue was also studied. desB mutants exhibited lower cytotoxicity in A549 cells. In addition, more pro-inflammatory cytokines and chemokines were present in desB mutant-treated. In the lungs of mouse model, WT survived longer than desB mutant, and the WT migrated from the lung to the liver and spleen. The results suggest that P. aeruginosa DesB affects the pathogenicity of the organism in the host.

Anti-Inflammatory Effect of a Peptide Derived from the Synbiotics, Fermented Cudrania tricuspidata with Lactobacillus gasseri, on Inflammatory Bowel Disease.

The objective of this study was to evaluate the effects of peptides derived from synbiotics on improving inflammatory bowel disease (IBD). Five-week-old male C57BL/6 mice were administered with dextran sulfate sodium (DSS) via drinking water for seven days to induce IBD (IBD group). The mice in the IBD group were orally administered with PBS (IBD-PBS-positive control), Lactobacillus gasseri 505 (IBD-Pro), fermented powder of CT extract with L. gasseri 505 (IBD-Syn), ß-casein: LSQSKVLPVPQKAVPYPQRDMP (IBD-Pep 1), or α s2-casein: VYQHQKAMKPWIQPKTKVIPYVRYL (IBD-Pep 2) (both peptides are present in the synbiotics) for four more days while inducing IBD. To confirm IBD induction, the weights of the animals and the disease activity index (DAI) scores were evaluated once every two days. Following treatment of probiotics, synbiotics, or peptides for 11 days, the mice were sacrificed. The length of the small and large intestines was measured. The expression of the proinflammatory cytokines IL-1ß, IL-6, TNF-α, and COX-2 in the large intestine was measured. Large intestine tissue was fixed in 10% formalin and stained with hematoxylin and eosin for histopathological analysis. The body weights decreased and DAI scores increased in the IBD group, but the DAI scores were lower in the IBD-Pep 2 group than those in the IBD group treated with PBS, Pro, Syn, or Pep 1. The lengths of the small and large intestines were shorter in the IBD group than in the group without IBD, and the expression levels of the proinflammatory cytokines were lower (p < 0.05) in the IBD-Pep 2 group than those in the IBD-PBS-positive control group. In addition, histopathological analysis showed that IBD was ameliorated in the Pep 2-treated group. These results indicate that Pep 2 derived from α s2-casein was effective in alleviating IBD-associated inflammation. Thus, we showed that these peptides can alleviate inflammation in IBD.

Asymptomatic Clostridium perfringens Inhabitation in Intestine Can Cause Inflammation, Apoptosis, and Disorders in Brain.

Clostridium perfringens (CP) is a foodborne pathogen. The bacterium can also inhabit human gut without symptoms of foodborne illness. However, the clinical symptoms of long-term inhabitation have not been known yet. Therefore, the objective of this study was to elucidate the relationship between intestinal CP and other internal organs. Phosphate-buffered saline (PBS) and CP were orally injected into 5-week-old (YOUNG) and 12-month-old C57BL6/J (ADULT) mice. Gene expression levels related to inflammation (tumor necrosis factor-α [TNF-α], interleukin [IL]-1ß, and IL-6) and oxidative stress (superoxide dismutase [SOD]1, SOD2, SOD3, glutathione reductase [GSR], glutathione peroxidase [GPx]3, and catalase [CAT]) responses were evaluated in the brain, small intestine, and liver. In addition, apoptosis-related (BCL2-associated X [BAX]1 and high-mobility group box-1 [HMGB1]) and brain disorder-related genes (CCAAT-enhancer-binding protein [C/EBP]-ß, C/EBPδ, C/EBP homologous protein [CHOP], and amyloid precursor protein [APP]) as brain damage markers were examined. The protein expressions in the brain were also measured. Gene expression levels of inflammation and oxidative stress responses were higher (p < 0.05) in brains of CP-YOUNG and CP-ADULT mice, compared with PBS-YOUNG and PBS-ADULT, and the gene expression levels were higher (p < 0.05) in brains of CP-ADULT mice than CP-YOUNG mice. Apoptosis-related (BAX1 and HMGB1) and brain disorder-related genes (C/EBPß, C/EBPδ, CHOP, and APP) were higher (p < 0.05) in brains of CP-challenged mice, compared with PBS-challenged mice. Even oxidative stress response (GPx and SOD2), cell damage-related (HMGB1), and ß-amyloid proteins were higher (p < 0.05) in brains of CP- than in PBS-challenged mice. C/EBP protein was higher (p < 0.05) in CP-YOUNG, compared with PBS-YOUNG mice. However, these clinical symptoms were not observed in small intestine and liver. These results indicate that although asymptomatic intestinal CP do not cause foodborne illness, their inhabitation may cause brain inflammation, oxidative stress, apoptosis, and cell damage, which may induce disorders, especially for the aged group.

Combined Enrichment and Quantitative Polymerase Chain Reaction to Improve Sensitivity and Reduce Time of Detection of Listeria monocytogenes in Mushrooms.

This study evaluated a combined method for the detection of Listeria monocytogenes in mushrooms, involving enrichment and quantitative real-time polymerase chain reaction (qPCR), to improve sensitivity and reduce detection time. The growth of L. monocytogenes was evaluated in Listeria enrichment broth (LEB) with modified carbon and nitrogen sources, increasing sodium concentrations, and added micronutrients. Primers targeting the L. monocytogenes iap (iap1 and iap2), hlyA (hlyA1-hlyA6), and prfA (prfA1-prfA4) genes were developed and their sensitivity and specificity were evaluated. The greatest increase in L. monocytogenes cell count was observed after 6-h incubation at 30°C in LEB+2 × FAC (LEB plus 20 mL/L ferric ammonium citrate), where cell count increased by 1.4 log CFU (colony-forming unit)/mL, compared with 0.9 log CFU/mL in LEB (p < 0.05). iap2 primers targeting the iap gene showed high specificity and were the most sensitive among those tested, with a detection limit of 2 log CFU/mL in LEB medium, 3.1 log CFU/g in golden needle mushroom, and 3.5 log CFU/g in large oyster mushroom. When applied to detection in golden needle mushrooms, a combination of 3-h incubation in LEB+2 × FAC medium and qPCR analysis with iap2 primers permitted detection of L. monocytogenes, even at an inoculum of 1 log CFU/g. Similarly, in large oyster mushrooms, 10-h enrichment in LEB+2 × FAC medium resulted in a cell count of 3.7 log CFU/g. These results indicate that a combined detection method, using LEB+2 × FAC medium for enrichment followed by qPCR with iap2 primer pair, can reduce enrichment time and improve the sensitivity and specificity of L. monocytogenes detection in mushrooms.

Vitamin E (α-tocopherol) consumption influences gut microbiota composition.

This study evaluated if vitamin E consumption affects gut microbiota. Mice were grouped into control, low vitamin E (LV), and high vitamin E (HV). LV and HV were fed DL-α-tocopherol at 0.06 mg/20 g and 0.18 mg/20 g of body weight per day, respectively, for 34 days. Body weight of mice was measured before and after vitamin E treatment. Animals were sacrificed, liver, spleen, small intestine and large intestine collected, and weight and length were measured. Composition of gut microbiota was determined by microbiome analysis. Spleen weight index of LV was the highest. However, liver weight indices and intestinal lengths were not different. Body weights of LV group were higher than those of control. Ratio of Firmicutes to Bacteroidetes was different in LV compared to control and HV. These results indicate that low-level consumption of vitamin E increases spleen and body weight, and changes gut microbiota.

The risk of aerotolerant Campylobacter jejuni strains in poultry meat distribution and storage.

Poultry meat is a major vector for Campylobacter jejuni foodborne illness. Since C. jejuni is microaerophillic, the cell counts gradually decreased during distribution and display under aerobic condition. However, if the pathogen can resist to aerobic condition, it may cause serious problem in food safety. This study determined the aerotolerance of C. jejuni isolated from poultry and the risk of the aerotolerant C. jejuni strains. Fourteen C. jejuni strains isolated from poultry were subjected to aerobic condition in a shaking incubator at 500 rpm and 37 °C. The cell counts of C. jejuni strains were enumerated on modified CCDA-Preston at 0, 24, 72 and 120 h, and the strains, having reduction less than 2 Log CFU/mL for 120 h were determined as aerotolerant C. jejuni strain. Non-aerotolerant and aerotolerant C. jejuni strains were then incubated at 4 °C under aerobic condition to compare the growth between aerotolerant and non-aerotolerant strains. In addition, transcriptomes for virulence and stress response genes (cadF, cdtB, ciaB, clpP and htrB) were compared between non-aerotolerant and aerotolerant C. jejuni strains. Among 14 C. jejuni strains, seven strains (50%) showed less than 2-Log CFU/mL reduction at 37 °C after 24 h, and five strains of them still showed less than 2-Log CFU/mL reduction after 48 h. Especially, C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16 were still survived after 120 h under aerobic condition, which were then determined as aerotolerant C. jejuni. However, at 4 °C under aerobic condition, there were no significant differences in the reduction of C. jejuni cell counts and virulence gene expressions between non-aerotolerant (C. jejuni SMFM2014-Du8) and aerotolerant strains (C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16) except for stress response gene (htrB). These results indicate that there are aerotolerant C. jejuni strains, but their risk is similar to non-aerotolerant C. jejuni strains at 4 °C under aerobic condition, which is distribution and storage condition for poultry meat. Therefore, additional food safety management for the aerotolerant C. jejuni is not necessary.

Quantitative microbial risk assessment of Campylobacter jejuni in jerky in Korea.

OBJECTIVE: The objective of this study was to estimate the risk of Campylobacter jejuni (C. jejuni) infection from various jerky products in Korea. METHODS: For the exposure assessment, the prevalence and predictive models of C. jejuni in the jerky and the temperature and time of the distribution and storage were investigated. In addition, the consumption amounts and frequencies of the products were also investigated. The data for C. jejuni for the prevalence, distribution temperature, distribution time, consumption amount, and consumption frequency were fitted with the @RISK fitting program to obtain appropriate probabilistic distributions. Subsequently, the dose-response models for Campylobacter were researched in the literature. Eventually, the distributions, predictive model, and dose-response model were used to make a simulation model with @RISK to estimate the risk of C. jejuni foodborne illness from the intake of jerky. RESULTS: Among 275 jerky samples, there were no C. jejuni positive samples, and thus, the initial contamination level was statistically predicted with the RiskUniform distribution [RiskUniform (-2, 0.48)]. To describe the changes in the C. jejuni cell counts during distribution and storage, the developed predictive models with the Weibull model (primary model) and polynomial model (secondary model) were utilized. The appropriate probabilistic distribution was the BetaGeneral distribution, and it showed that the average jerky consumption was 51.83 g/d with a frequency of 0.61%. The developed simulation model from this data series and the dose-response model (Beta Poisson model) showed that the risk of C. jejuni foodborne illness per day per person from jerky consumption was 1.56×10-12. CONCLUSION: This result suggests that the risk of C. jejuni in jerky could be considered low in Korea.

Serotyping and Genotyping Characterization of Pathogenic Escherichia coli Strains in Kimchi and Determination of Their Kinetic Behavior in Cabbage Kimchi During Fermentation.

This study determined the serotyping and genotyping properties of Escherichia coli strains isolated from kimchi and various raw vegetables used for kimchi preparation. In addition, the kinetic behavior of E. coli strains in kimchi during fermentation was also determined using a predictive microbiological model. The study results revealed that E. coli isolated from napa cabbage (3.3%; 1/30) was enterohemorrhagic E. coli (O6:H34), and eight typical colonies isolated from kimchi (15%; 6/40) were enteropathogenic E. coli (H8, H8, H12, H34, H30, O20:H39, H39, and H12). The genetic correlation of the strains did not show close genetic correlations. On the other hand, the kinetic behavior of E. coli strains in kimchi during fermentation using a predictive Baranyi model (primary model) and a polynomial equation (secondary model), followed by validation by calculating root mean square error (RMSE), revealed that the pathogenic E. coli cell counts increased (with RMSE of 0.280 in growth curve) in the early stage of fermentation and decreased (with RMSE of 0.920 in death curve) thereafter depending on fermentation temperature. Therefore, this finding indicated that pathogenic E. coli isolated from kimchi and related vegetables underwent proliferation at the beginning of fermentation, which decreased thereafter. Thus, these results of this study suggest intake of sufficiently fermented kimchi to prevent potential foodborne illness due to pathogenic E. coli.

Microbiological safety of processed meat products formulated with low nitrite concentration - A review.

Nitrite plays a major role in inhibiting the growth of foodborne pathogens, including Clostridium botulinum (C. botulinum) that causes botulism, a life-threatening disease. Nitrite serves as a color-fixing agent in processed meat products. However, N-nitroso compounds can be produced from nitrite, which are considered as carcinogens. Thus, consumers desire processed meat products that contain lower concentrations (below conventional concentrations of products) of nitrite or no nitrite at all, although the portion of nitrite intake by processed meat consumption in total nitrite intake is very low. However, lower nitrite levels might expose consumers to risk of botulism poisoning due to C. botulinum or illness caused by other foodborne pathogens. Hence, lower nitrite concentrations in combination with other factors such as low pH, high sodium chloride level, and others have been recommended to decrease the risk of food poisoning. In addition, natural compounds that can inhibit bacterial growth and function as color-fixing agents have been developed to replace nitrite in processed meat products. However, their antibotulinal effects have not been fully clarified. Therefore, to have processed meat products with lower nitrite concentrations, low pH, high sodium chloride concentration, and others should also be applied together. Before using natural compounds as replacement of nitrite, their antibotulinal activities should be examined.

Invited review: Microbe-mediated aflatoxin decontamination of dairy products and feeds.

Aspergillus flavus, Aspergillus parasiticus, and Aspergillus nomius contaminate corn, sorghum, rice, peanuts, tree nuts, figs, ginger, nutmeg, and milk. They produce aflatoxins, especially aflatoxin B1, which is classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Many studies have focused on aflatoxin removal from food or feed, especially via microbe-mediated mechanisms-either adsorption or degradation. Of the lactic acid bacteria, Lactobacillus rhamnosus GG efficiently binds aflatoxin B1, and a peptidoglycan in the bacterium cell wall plays an important role. This ability of L. rhamnosus GG should be applied to the removal of aflatoxin B1. Aflatoxin can be removed using other aflatoxin-degrading microorganisms, including bacterial and fungal strains. This review explores microbe-associated aflatoxin decontamination, which may be used to produce aflatoxin-free food or feed.

Effects of low NaNO2 and NaCl concentrations on Listeria monocytogenes growth in emulsion-type sausage.

OBJECTIVE: The objective of this study was to evaluate the effect of combinations of NaNO2 and NaCl concentrations on Listeria monocytogenes (L. monocytogenes) growth in emulsion-type sausage. METHODS: Emulsion-type sausages formulated with different combinations of NaNO2 (0 and 10 ppm) and NaCl (1.00%, 1.25%, and 1.50%) were inoculated with a five-strain L. monocytogenes mixture, and stored at 4°C, 10°C, and 15°C, under aerobic or vacuum conditions. L. monocytogenes cell counts were measured at appropriate intervals, and kinetic parameters such as growth rate and lag phase duration (LPD) were calculated using the modified Gompertz model. RESULTS: Growth rates increased (0.004 to 0.079 Log colony-forming unit [CFU]/g/h) as storage temperature increased, but LPD decreased (445.11 to 8.35 h) as storage temperature and NaCl concentration increased. The effect of combinations of NaCl and low-NaNO2 on L. monocytogenes growth was not observed at 4°C and 10°C, but it was observed at 15°C, regardless of atmospheric conditions. CONCLUSION: These results indicate that low concentrations of NaNO2 and NaCl in emulsion-type sausage may not be sufficient to prevent L. monocytogenes growth, regardless of whether they are vacuum-packaged and stored at low temperatures. Therefore, additional techniques are necessary for L. monocytogenes control in the product.

Quantitative Microbial Risk Assessment for Clostridium perfringens in Natural and Processed Cheeses.

This study evaluated the risk of Clostridium perfringens (C. perfringens) foodborne illness from natural and processed cheeses. Microbial risk assessment in this study was conducted according to four steps: hazard identification, hazard characterization, exposure assessment, and risk characterization. The hazard identification of C. perfringens on cheese was identified through literature, and dose response models were utilized for hazard characterization of the pathogen. For exposure assessment, the prevalence of C. perfringens, storage temperatures, storage time, and annual amounts of cheese consumption were surveyed. Eventually, a simulation model was developed using the collected data and the simulation result was used to estimate the probability of C. perfringens foodborne illness by cheese consumption with @RISK. C. perfringens was determined to be low risk on cheese based on hazard identification, and the exponential model (r = 1.82×10(-11)) was deemed appropriate for hazard characterization. Annual amounts of natural and processed cheese consumption were 12.40±19.43 g and 19.46±14.39 g, respectively. Since the contamination levels of C. perfringens on natural (0.30 Log CFU/g) and processed cheeses (0.45 Log CFU/g) were below the detection limit, the initial contamination levels of natural and processed cheeses were estimated by beta distribution (α 1 = 1, α 2 = 91; α 1 = 1, α 2 = 309)×uniform distribution (a = 0, b = 2; a = 0, b = 2.8) to be -2.35 and -2.73 Log CFU/g, respectively. Moreover, no growth of C. perfringens was observed for exposure assessment to simulated conditions of distribution and storage. These data were used for risk characterization by a simulation model, and the mean values of the probability of C. perfringens foodborne illness by cheese consumption per person per day for natural and processed cheeses were 9.57×10(-14) and 3.58×10(-14), respectively. These results indicate that probability of C. perfringens foodborne illness by consumption cheese is low, and it can be used to establish microbial criteria for C. perfringens on natural and processed cheeses.

Development of postbiotics by bioconverting whey using Lactobacillus plantarum SMFM2017-YK1 and Limosilactobacillus fermentum SMFM2017-NK1 to alleviate periodontitis.

This study investigated the effects of whey bioconversion products (WBPs) produced by lactic acid bacteria on periodontal disease. WBPs were prepared by fermenting whey with seven lactic acid bacteria, Limosilactobacillus fermentum SMFM2017-CK1 (LF-CK1), L. plantarum SMFM2017-NK2 (LP-NK2), Pediococcus pentosaceus SMFM2017-NK1 (PP-NK1), L. plantarum SMFM2017-NK1 (LP-NK1), L. paraplantarum SMFM2017-YK1 (LPP-YK1), L. plantarum SMFM2017-YK1 (LP-YK1), and L. fermentum SMFM2017-NK1 (LF-NK1)]; the pH of the fermented whey was adjusted to 6.5, followed by centrifugation. WBPs were examined for their effect on cell viability and antimicrobial activity against periodontal pathogens. The selected WBPs were used in animal experiments. After inducing periodontitis through right mandibular first molar ligation, WBPs were administered orally for 8 weeks. After sacrifice, gene and protein expression analyses of genes related to inflammatory and oxidative stress were performed, and histopathological analysis of gingival tissue was conducted. Our results showed that LP-YK1 WBP (WBP produced by LP-YK1) and LF-NK1 WBP (WBP produced by LF-NK1) groups exerted higher anti-inflammatory and antioxidant effects compared to the control group (p < 0.05). Histopathological analysis revealed that infiltration of inflammatory cells and epithelial cell proliferation were reduced in the LP-YK1 WBP group. These results indicate that WBPs prepared with LP-YK1 can be used as a postbiotic to alleviate periodontitis.

Isolation of Bacillus cereus from Soft Soybean Curd and the Kinetic Behavior of B. cereus Isolates at Changing Temperatures.

ABSTRACT: In this study, Bacillus cereus was isolated from soft soybean curds, and a dynamic model was developed to describe the kinetic behavior of these isolates during transfer and storage. B. cereus isolates recovered from soft soybean curds were inoculated into soft soybean curd, and the levels were determined during storage at 10 to 30°C. The B. cereus counts were fitted to the Baranyi model to calculate maximum growth rate (µmax) and lag-phase duration (LPD). These kinetic parameters were then analyzed with a polynomial equation to evaluate the effects of temperature on the kinetic parameters. The developed model was validated with observed values, and the differences between predicted and observed values were determined by calculating the root mean square error (RMSE). A dynamic model was then developed with a combination of primary and secondary models to describe B. cereus growth under changing temperature conditions. B. cereus was detected in two soft soybean curd samples (5.1%) at 0.7 log CFU/g. The µmax was -0.04 to 0.47 log CFU/g/h, and the ln(LPD) was 3.94 to 0.04 h, depending on the storage temperature. The model performance was appropriate with a 0.216 RMSE and accurately described the kinetic behavior of B. cereus in soft soybean curd samples. These results suggest that B. cereus can contaminate soft soybean curds and that the models developed with the B. cereus isolates are useful for describing the kinetic behavior of B. cereus in soft soybean curd.

Improvement of the detection efficiency of 3M™ molecular detection system for Campylobacter in poultry using nitrogen-doped carbon nanodots.

This study was performed to examine whether the use of nitrogen-doped carbon nanodots (N-CNDs) can improve the detection sensitivity of the 3 M™ molecular detection system (MDS) for Campylobacter. N-CNDs were added to a Campylobacter enrichment broth (CEB) at concentrations of 5 and 10 mg/mL (NCEB-5 and NCEB-10, respectively). Campylobacter coli, C. jejuni, and C. lari were inoculated into the broths. The broth cultures were then irradiated with light-emitting diode (LED) at 425 nm for 1 h and incubated at 42 °C for 6 h, and then grown on modified charcoal cefoperazone deoxycholate agar (mCCDA). The detection rates of the MDS and a conventional method (plating an enriched sample on mCCDA and analyzing a colony on mCCDA with PCR) for Campylobacter in chicken and duck carcasses were compared. The detection rates from the MDS were compared after enrichment in CEB and NCEB-5 at 3, 5, 6, 7, 9, 12, and 24 h. When 5 mg/mL of N-CNDs was added to the CEB followed by irradiation at 425 nm, growth of the Campylobacter was accelerated. In addition, the qualitative test was more sensitive in the MDS than in the conventional method, and the detection time was shortened in CEB enriched with N-CNDs. These results indicate that adding N-CNDs to CEB can improve the detection efficiency of MDS.

Contamination of Clostridium perfringens in soy sauce, and quantitative microbial risk assessment for C. perfringens through soy sauce consumption.

The objective of this study was to conduct QMRA (quantitative microbial risk assessment) of Clostridium perfringens through soy sauce consumption. Four hundred and ninety soy sauce samples from markets were analyzed to detect C. perfringens. Temperature and time were also measured during transportation and display of soy sauce. A primary model was developed by fitting the Weibull model to the C. perfringens cell counts in soy sauce at 7-35°C, and δ (the time needed to decrease 1 log CFU/ml) and ρ (curve shape) were calculated. The parameters were analyzed, using the Exponential model (secondary model) as a function of temperature. The consumption amount and percentage of soy sauce were surveyed, and a dose-response model was searched. Using all collected data, a simulation model was prepared in the @RISK program to estimate the probability of C. perfringens foodborne illness by soy sauce consumption. C. perfringens were negative in 490 samples. Thus, the initial contamination level was estimated to be -2.9 log CFU/ml. The developed predictive models showed that C. perfringens cell counts decreased during transportation and display. The average consumption amounts, and the percentage of soy sauce were 7.81 ml and 81.2%, respectively. The simulation showed that the probability of C. perfringens foodborne illness by consumption of soy sauce was 1.7 × 10-16 per person per day. Therefore, the risk of C. perfringens by consumption of soy sauce is low in Korea.

Development of a Selective Agar for Improving Campylobacter jejuni Detection in Food.

BACKGROUND: Campylobacter jejuni is a major gastroenteritis-causing foodborne pathogen. However, it is difficult to isolate when competing bacteria or cold-damaged cells are present. OBJECTIVE: Herein, a medium (Campylobacter selective agar, CSA) was developed and supplemented with catalase, L-serine, L-cysteine, and quercetin for the selective detection of C. jejuni in food. METHOD: The C. jejuni-detection efficiency in media broth and chicken tenders was evaluated. The pathogen was enumerated on modified charcoal-cefoperazone-deoxycholate agar (mCCDA), CSA supplemented with 4 µM catalase (CSA-C4), 8 µM catalase (CSA-C8), 20 mM L-serine (CSA-S20) or 50 mM L-serine (CSA-S50), and mCCDA supplemented with 0.5 mM L-cysteine (mCCDA-LC0.5), 1 mM L-cysteine (mCCDA-LC1), 40 µM quercetin (mCCDA-Q40) or 320 µM quercetin (mCCDA-Q320). The detection efficiency was then evaluated by counting colonies on the selective agar media. Quantitative assessment was also performed using chicken and duck carcasses. RESULTS: The C. jejuni detection efficiencies were higher (P < 0.05) in the groups CSA-C4 or CSA-C8, and CSA-S20 or CSA-S50, than mCCDA, and the detection efficiencies were maintained even in the presence of Acinetobacter baumannii, a competing bacterium. In the quantitative test, CSA-C8 and CSA-S50 demonstrated higher C. jejuni-detection efficiencies than mCCDA (control). CONCLUSIONS: Therefore, CSA-C8 and CSA-S50 improved the detection efficiency of C. jejuni in poultry products by promoting the recovery of cold-damaged cells. HIGHLIGHTS: When using CSA-C8 or CSA-S50 developed in this study for detection of C. jejuni in food, detection efficiency was higher than mCCDA.

High Prevalence of Listeria monocytogenes in Smoked Duck: Antibiotic and Heat Resistance, Virulence, and Genetics of the Isolates.

This study aimed at determining the genetic and virulence characteristics of the Listeria monocytogenes from smoked ducks. L. monocytogenes was isolated by plating, and the isolated colonies were identified by PCR. All the obtained seven L. monocytogenes isolates possessed the virulence genes (inlA, inlB, plcB, and hlyA) and a 385 bp actA amplicon. The L. monocytogenes isolates (SMFM2018 SD 1-1, SMFM 2018 SD 4-1, SMFM 2018 SD 4-2, SMFM 2018 SD 5-2, SMFM 2018 SD 5-3, SMFM 2018 SD 6-2, and SMFM 2018 SD 7-1) were inoculated in tryptic soy broth (TSB) containing 0.6% yeast extract at 60°C, followed by cell counting on tryptic soy agar (TSA) containing 0.6% yeast extract at 0, 2, 5, 8, and 10 min. We identified five heat resistant isolates compared to the standard strain (L. monocytogenes ATCC13932), among which three exhibited the serotype 1/2b and D-values of 5.41, 6.48, and 6.71, respectively at 60°C. The optical densities of the cultures were regulated to a 0.5 McFarland standard to assess resistance against nine antibiotics after an incubation at 30°C for 24 h. All isolates were penicillin G resistant, possessing the virulence genes (inlA, inlB, plcB, and hlyA) and the 385-bp actA amplicon, moreover, three isolates showed clindamycin resistance. In conclusion, this study allowed us to characterize L. monocytogenes isolates from smoked ducks, exhibiting clindamycin and penicillin G resistance, along with the 385-bp actA amplicon, representing higher invasion efficiency than the 268-bp actA, and the higher heat resistance serotype 1/2b.

Erratum to: Description of Kinetic Behavior of Pathogenic Escherichia coli in Cooked Pig Trotters under Dynamic Storage Conditions Using Mathematical Equations.

[This corrects the article DOI: 10.5851/kosfa.2020.e64.].