Three gastroenteritis outbreaks in South Korea caused by the consumption of kimchi tainted by norovirus GI.4

Survival of O157 and non-O157 shiga toxin-producing Escherichia coli in Korean style kimchi

Korean style kimchi contaminated with Shiga toxin-producing Escherichia coli (STEC) O157:H7 was the cause of an outbreak in Canada from December 2021 to January 2022. To determine if this STEC O157:H7 has greater potential for survival in kimchi than other STEC, the outbreak strain and six other STEC strains (O26:H11, O91:H21, O103:H2, O121:H19, and two O157:H7) were inoculated individually at 6 to 6.5 log CFU/g into commercially sourced kimchi and incubation at 4 °C. At intervals of seven days inoculated and control kimchi was plated onto MacConkey agar to enumerate lactose utilising bacteria. The colony counts were interpreted as enumerating the inoculated STEC, since no colonies were observed on MacConkey agar plated with uninoculated kimchi. Over eight weeks of incubation the pH was stable at 4.10 to 4.05 and the STEC strains declined by 0.7-1.0 log, with a median reduction of 0.9 log. The linear rate of reduction of kimchi outbreak STEC O157:H7 was -0.4 log per 30 days (Slope Uncertainty 0.05), which was not significantly different from the other O157 and nonO157 STEC strains (P = 0.091). These results indicate that the outbreak was not due to the presence of strain better adapted to survival in kimchi than other STEC, and that STEC can persist in refrigerated Korean style kimchi with a minimal decline over the shelf-life of the product.

Does kimchi deserve the status of a probiotic food?

Kimchi is a traditional fermented vegetable side dish in Korea and has become a global health food. Kimchi undergoes spontaneous fermentation, mainly by lactic acid bacteria (LAB) originating from its raw ingredients. Numerous LAB, including the genera Leuconostoc, Weissella, and Lactobacillus, participate in kimchi fermentation, reaching approximately 9-10 log colony forming units per gram or milliliter of food. The several health benefits of LAB (e.g., antioxidant and anti-inflammatory properties) combined with their probiotic potential in complex diseases including obesity, cancer, atopic dermatitis, and immunomodulatory effect have generated an interest in the health effects of LAB present in kimchi. In order to estimate the potential of kimchi as a probiotic food, we comprehensively surveyed the health functionalities of kimchi and kimchi LAB, and their effects on human gut environment, highlighting the probiotics function.

Two Faces of Fermented Foods-The Benefits and Threats of Its Consumption

In underdeveloped and developing countries, due to poverty, fermentation is one of the most widely used preservation methods. It not only allows extending the shelf life of food, but also brings other benefits, including inhibiting the growth of pathogenic microorganisms, improving the organoleptic properties and product digestibility, and can be a valuable source of functional microorganisms. Today, there is a great interest in functional strains, which, in addition to typical probiotic strains, can participate in the treatment of numerous diseases, disorders of the digestive system, but also mental diseases, or stimulate our immune system. Hence, fermented foods and beverages are not only a part of the traditional diet, e.g., in Africa but also play a role in the nutrition of people around the world. The fermentation process for some products occurs spontaneously, without the use of well-defined starter cultures, under poorly controlled or uncontrolled conditions. Therefore, while this affordable technology has many advantages, it can also pose a potential health risk. The use of poor-quality ingredients, inadequate hygiene conditions in the manufacturing processes, the lack of standards for safety and hygiene controls lead to the failure food safety systems implementation, especially in low- and middle-income countries or for small-scale products (at household level, in villages and scale cottage industries). This can result in the presence of pathogenic microorganisms or their toxins in the food contributing to cases of illness or even outbreaks. Also, improper processing and storage, as by well as the conditions of sale affect the food safety. Foodborne diseases through the consumption of traditional fermented foods are not reported frequently, but this may be related, among other things, to a low percentage of people entering healthcare care or weaknesses in foodborne disease surveillance systems. In many parts of the world, especially in Africa and Asia, pathogens such as enterotoxigenic and enterohemorrhagic Escherichia coli, Shigella spp., Salmonella spp., enterotoxigenic Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus have been detected in fermented foods. Therefore, this review, in addition to the positive aspects, presents the potential risk associated with the consumption of this type of products.

Viruses in fermented foods: are they good or bad? Two sides of the same coin

The emergence of Coronavirus disease 2019 as a global pandemic has increased popular concerns about diseases caused by viruses. Fermented foods containing high loads of viable fungi and bacteria are potential sources for virus contamination. The most common include viruses that infect bacteria (bacteriophage) and yeasts reported in fermented milks, sausages, vegetables, wine, sourdough, and cocoa beans. Recent molecular studies have also associated fermented foods as vehicles for pathogenic human viruses. Human noroviruses, rotavirus, and hepatitis virus have been identified in different fermented foods through multiple routes. No severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) virus or close members were found in fermented foods to date. However, the occurrence/persistence of other pathogenic viruses reveals a potential vulnerability of fermented foods to SARS-CoV-2 contamination. On the other side of the coin, some bacteriophages are being suggested for improving the fermentation process and food safety, as well as owing potential probiotic properties in modern fermented foods. This review will address the diversity and characteristics of viruses associated with fermented foods and what has been changed after a short introduction to the most common next-generation sequencing platforms. Also, the risk of SARS-CoV-2 transmission via fermented foods and preventive measures will be discussed.

Recent (2011-2017) foodborne outbreak cases in the Republic of Korea compared to the United States: a review

This study analyzes and compares foodborne disease outbreaks reported in the Republic of Korea (KR) and the United States (US) during 2011-2017. The foodborne outbreaks data in the KR and the US were collected from the Ministry of Food and Drug Safety and from the Surveillance for Foodborne Disease Outbreaks United States, respectively. The average number of outbreaks and illness population were higher in the US than in the KR, but the KR's illness ratio considering population size was 2.4 times higher than that of the US. When the sites of outbreaks compared, the number of illness was the highest at schools in the KR whereas outbreaks at restaurants were more frequent in the US. In the KR, bacterial infections were the primary cause of outbreaks while bacterial and viral infections accounted for the largest share of outbreaks in the US. Specifically, pathogenic E. coli presented a significant risk in the KR whereas Salmonella was the most prevalent in the US. These results indicate that the main microbiological targets for detection and control in the KR should differ from the US, which should be considered for developing food safety related policies.

Nationwide seroprevalence of hepatitis A in South Korea from 2009 to 2019

Hepatitis A, an acute type of hepatitis caused by the hepatitis A virus, occurs worldwide. Following the 2009 hepatitis A epidemic in South Korea, patient outbreak reports were collectively converted to an “all-patient report” in 2011, and national immunization programs were introduced for children in 2015. In this study, we aimed to analyze the changes and characteristics of hepatitis A antibody titers in South Korea following the epidemic. The results of hepatitis A antibody tests performed at clinical laboratories from 2009 to 2019 were analyzed based on year, age, region, sex, and medical institution. The average 2009–2018 positive anti-hepatitis A virus immunoglobulin G rate was 51.8%, but it increased (56.06%) in 2019. Significantly different antibody-positive rates were observed based on age: <10 years, 54.5%; 20–29 years, 19.5%; ≥50 years, almost 100%. The positive rate of individuals in their teens and 20s gradually increased, whereas that of those in their 30s and 40s gradually decreased. Males had higher antibody-positive rates than females, and samples from higher-level general hospitals exhibited higher antibody rates. The positive anti-hepatitis A virus immunoglobulin M rates gradually decreased after 2009 and were <1% after 2012. However, a high positive rate of 3.69% was observed in 2019 when there was an epidemic. Anti-hepatitis A virus immunoglobulin G-positive rates were similar throughout the year, but the anti-hepatitis A virus immunoglobulin M-positive rates increased from January, peaked in April, and decreased from July, exhibiting distinct seasonality. This is considered to be related to groundwater pollution during the spring drought season. The introduction of the “all-patient report” and national vaccination program for children has had an effective influence on hepatitis A management. However, for hepatitis A prevention, policy considerations for high-risk age groups with low antibody-positive rates will be necessary.

Assessment of human norovirus inhibition in cabbage kimchi by electron beam irradiation using RT-qPCR combined with immunomagnetic separation

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 < 0.05). HuNoV levels in cabbage Kimchi were also significantly reduced to 0.26 to 1.57 log₁₀ copy number/mL following irradiation with 1 to 10 kGy (P < 0.05) compared to positive control (6.0 log₁₀ copy number/mL). The D-values for 1 log₁₀ reduction (90% inhibition) of HuNoV in suspension and cabbage Kimchi were 4.94 and 6.96 kGy of e-beam, respectively. The pH and acidity in the irradiated cabbage Kimchi were 4.41 to 4.58 and 0.61% to 0.71%, respectively, indicating that e-beam did not affect the optimal pH or acidity. Although a slight increase of greenness was observed in the leaf portion of cabbage Kimchi irradiated with 7 to 10 kGy of e-beam, this color change was minimal and went undetected by panelists in the sensorial evaluation. The five properties of sensorial quality assessed were no different in the irradiated Kimchi sample compared with the control sample (nonirradiated cabbage Kimchi). Therefore, this study suggests that ≥6.96 kGy of e-beam could be applied in the cabbage Kimchi industry to obtain >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.

Interaction between norovirus and Histo-Blood Group Antigens: A key to understanding virus transmission and inactivation through treatments?

Human noroviruses (HuNoVs) are a main cause of acute gastroenteritis worldwide. They are frequently involved in foodborne and waterborne outbreaks. Environmental transmission of the virus depends on two main factors: the ability of viral particles to remain infectious and their adhesion capacity onto different surfaces. Until recently, adhesion of viral particles to food matrices was mainly investigated by considering non-specific interactions (e.g. electrostatic, hydrophobic) and there was only limited information about infectious HuNoVs because of the absence of a reliable in vitro HuNoV cultivation system. Many HuNoV strains have now been described as having specific binding interactions with human Histo-Blood Group Antigens (HBGAs) and non-HBGA ligands found in food and the environment. Relevant approaches to the in vitro replication of HuNoVs were also proposed recently. On the basis of the available literature data, this review discusses the opportunities to use this new knowledge to obtain a better understanding of HuNoV transmission to human populations and better evaluate the hazard posed by HuNoVs in foodstuffs and the environment.

Surveillance of norovirus contamination in commercial fresh/frozen berries from Heilongjiang Province, China, using a TaqMan real-time RT-PCR assay

Norovirus (NoV), a major food-borne virus, causes non-bacterial acute gastroenteritis in humans. Berries are generally harvested from low-growing bushes by hand and are minimally processed before being sold to consumers. Therefore, the consumption of berries has been linked to numerous food-borne gastroenteritis outbreaks caused by NoV in many countries. We performed a survey of NoV contamination in commercial fresh/frozen berry fruits collected from 2016 to 2017 in the Heilongjiang Province, the main berry-producing area in China, using a TaqMan-based real-time reverse transcription-PCR assay. Among 900 frozen and 900 fresh domestic retail berry samples, the prevalence of NoV was 9% (81/900) and 12.11% (109/900), including 35.80% (29/81) and 29.36% (32/109) of genotype GI alone, 54.32% (44/81) and 60.55% (66/109) of GII alone, and 9.88% (8/81) and 10.09% (11/109) of both GI and GII, respectively. No NoV was detected among the 677 frozen berry samples for export. Thus, the occurrence of NoV contamination was significantly higher in domestic berries than in exported berries and higher in fresh berries than in frozen berries. This study highlights the need for further risk surveillance for NoV contamination in berries produced in the Heilongjiang Province and recommends region-extended monitoring of retail berries for NoV.

Foodborne Infectious Diseases Mediated by Inappropriate Infection Control in Food Service Businesses and Relevant Countermeasures in Korea

Objectives

The objective of this review is to propose an appropriate course of action for improving the guidelines followed by food handlers for control of infection. For this purpose, previous epidemiological reports related to acute gastroenteritis in food service businesses mediated by food handlers were intensively analyzed.

Methods

Relevant studies were identified in international databases. We selected eligible papers reporting foodborne infectious disease outbreaks. Among primary literature collection, the abstract of each article was investigated to find cases that absolutely identified a causative factor to be food handlers’ inappropriate infection control and the taxon of causative microbial agents by epidemiological methodologies. Information about the sites (type of food business) where the outbreaks occurred was investigated.

Results

A wide variety of causative microbial agents has been investigated, using several epidemiological methods. These agents have shown diverse propagation pathways based on their own molecular pathogenesis, physiology, taxonomy, and etiology.

Conclusion

Depending on etiology, transmission, propagation, and microbiological traits, we can predict the transmission characteristics of pathogens in food preparation areas. The infected food workers have a somewhat different ecological place in infection epidemiology as compared to the general population. However, the current Korean Food Safety Act cannot propose detailed guidelines. Therefore, different methodologies have to be made available to prevent further infections.

Kimchi and Other Widely Consumed Traditional Fermented Foods of Korea: A Review

Different types of fermented foods such as chongkukjang, doenjang, ganjang, gochujang, and kimchi are plentifully available and widely consumed in north eastern Asian countries including Korea. Among them, kimchi is one of the most popular Korean traditional food. It is prepared by fermenting the baechu cabbage together with other vegetables and lactic acid bacteria (LAB) with functional potential. Many types of ingredients are added to kimchi to enhance its taste, flavor, nutritional value, texture etc. A number of bacteria are involved in the fermentation of kimchi, but LAB are the dominant species in the fermentation process. The addition of other sub ingredients and formation of different by-products during fermentation eventually leads to eradication of putrefactive and pathogenic bacteria, and also increase the functionalities, nutritional and nutraceutical potential of kimchi. Kimchi possesses anti-inflammatory, antibacterial, antioxidant, anticancer, antiobesity, probiotic properties, cholesterol reduction, and antiaging properties. In the present review an attempt has been made to review the different types of fermented foods found in the Korean peninsula with detailed scientific research regarding preparation, processing, structure of the microecosystem, and health benefits of kimchi.

An outbreak of norovirus infection associated with fermented oyster consumption in South Korea, 2013

An acute gastroenteritis (AGE) outbreak was reported in May 2013 in Gyeonggi Province, South Korea. Eight students who had eaten breakfast on 21 May 2013 at a high-school restaurant exhibited AGE symptoms. Our case-control study showed that a strong association was observed between AGE symptoms and fermented oyster consumption. Virological studies also indicated that noroviruses (NoVs) were detected from both clinical samples and fermented oyster samples, and multiple different genotypes (genogroups GII.4, GII.11 and GII.14) of NoVs were present in both samples. The nucleotide sequence similarity between the strains found in the clinical samples and those in the fermented oysters was more than 99·5%. Therefore, to prevent further outbreaks, proper management of raw oysters is necessary and the food industry should be aware of the risk of viral gastroenteritis posed by fermented oysters contaminated with NoVs.