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The diverse microbial communities in kimchi are dependent on fermentation period and temperature. Here, we investigated the effect of enterotoxigenic Escherichia coli (ETEC) during the fermentation of kimchi at two temperatures using high-throughput sequencing. There were no differences in pH between the control group, samples not inoculated with ETEC, and the ETEC group, samples inoculated with ETEC MFDS 1009477. The pH of the two groups, which were fermented at 10 and 25°C, decreased rapidly at the beginning of fermentation and then reached pH 3.96 and pH 3.62. In both groups, the genera Lactobacillus, Leuconostoc, and Weissella were predominant. Our result suggests that microbial communities during kimchi fermentation may be affected by the fermentation parameters, such as temperature and period, and not enterotoxigenic E. coli (ETEC).

These days, bacterial detection methods have some limitations in sensitivity, specificity, and multiple detection. To overcome these, novel detection and identification method is necessary to be developed. Recently, NGS panel method has been suggested to screen, detect, and even identify specific foodborne pathogens in one reaction. In this study, new NGS panel primer sets were developed to target 13 specific virulence factor genes from five types of pathogenic Escherichia coli, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium, respectively. Evaluation of the primer sets using singleplex PCR, crosscheck PCR and multiplex PCR revealed high specificity and selectivity without interference of primers or genomic DNAs. Subsequent NGS panel analysis with six artificially contaminated food samples using those primer sets showed that all target genes were multi-detected in one reaction at 10

Pathogenic Escherichia coli (PEc) is a leading cause of both foodborne and waterborne illness. In September 2012, a major foodborne outbreak with PEc occurred, affecting approximately 1,200 students and food handlers from 7 schools in Gyeonggi province, South Korea caused by contaminated kimchi. For detection of PEc in kimchi, real-time polymerase chain reaction (RT-PCR) and traditional culture methods were used. EAEC and ETEC genotypes were identified in samples from individuals with the illness and in kimchi using conventional PCR. Bacteria in stool samples were genetically similar to bacteria from kimchi (98% homology). PEc from kimchi was identified as the causative agent of a foodborne outbreak in South Korea. A significant link between kimchi and individuals with foodborne illnesses after consuming kimchi was demonstrated.

Microbiological quality of 206 raw ready-to-eat seafood samples was investigated according to species (gizzard shad, halibut, rockfish, tuna, oyster and squid) and distribution channels (fishery, hyper and online market). Enumeration of aerobic plate count and total coliforms (TC) and pathogenic bacteria (Bacillus cereus, Staphylococcus aureus and Vibrio parahaemolyticus) was performed, and level of microbiological quality was classified into four groups: satisfactory, acceptable, unsatisfactory and unacceptable. Qualitative analysis was also performed for Escherichia coli and eight foodborne pathogens (B. cereus, E. coli O157:H7, Listeria monocytogenes, Salmonella spp., S. aureus, Vibrio cholerae, V. parahaemolyticus, and Vibrio vulnificus). Raw ready-to-eat seafood products revealed 0·5% at an unsatisfactory level and 4·9% at an unacceptable level due to ≥4 log CFU g−1 of TC in squid and ≥3 log CFU g−1 of V. parahaemolyticus in gizzard shad respectively. Gizzard shad was shown to be potentially hazardous, as its sashimi is eaten with its skin attached. Bacillus cereus, E. coli, S. aureus, V. parahaemolyticus and V. vulnificus were qualitatively detected. Samples from the fishery market showed higher detection rate especially in V. parahaemolyticus (21·6%) and V. vulnificus (1·7%) which indicates the need to improve microbiological safety of raw ready-to-eat seafood products in fishery market. Significance and Impact of the Study Raw ready-to-eat seafood products like sashimi can be easily contaminated with various bacteria from aquatic environments and human reservoirs, which subsequently bring about a risk in food poisoning due to no heating process before consumption. The results of this study provide comprehensive microbiological data on various species of raw ready-to-eat seafood from various distribution channels. It may contribute to establish reasonable standard and effective strategies to ensure a good microbiological quality of raw ready-to-eat seafood for the safety of meals, like sashimi and sushi.

Estimating the actual occurrence of foodborne illness is challenging because only a small proportion of foodborne illnesses are confirmed and reported. Many studies have attempted to accurately estimate the overall number of cases of foodborne illness, but none have attempted to estimate the burden of foodborne disease in South Korea. This study used data from the Health Insurance Review and Assessment Service (HIRA), a public health surveillance system in South Korea, to calculate the number of cases and hospitalizations due to 18 specific pathogens and unspecified agents commonly transmitted through contaminated food between 2008 and 2012 in South Korea while accounting for uncertainty in the estimate. The estimated annual occurrences of foodborne illness were 336,138 (90% credible interval [CrI]: 258,379-430,740), with inpatient stays (hospitalizations), outpatient visits (foodborne disease infections), and patients' experiences (without visiting physicians) accounting for 2.3% (n=7809 [90% CrI: 7016-8616]), 14.4% (n=48,267 [90% CrI: 45,883-50,695]) and 83.3% (n=280,062 [90% CrI: 201,795-374,091]), respectively. Escherichia coli, including enterohemorrhagic E. coli, caused most illnesses, followed by nontyphoidal Salmonella spp., Staphylococcus aureus, hepatitis A virus, and norovirus. These results will be useful to food safety policymakers for the prevention and control of foodborne pathogens in South Korea.

We employed Caenorhabditis elegans as a model to study the effectiveness of sanitizers in killing pathogenic Escherichia coli strains ingested by free-living nematodes. Adult worms that had fed on six pathogenic E. coli strains (highly persistent in the nematode intestine) were treated with three chemical solutions. In planktonic cells, none of the H2O2 and acetic acid treatments influenced the survival of the pathogenic E. coli strains, whereas sodium hypochlorite critically decreased the viability of the strains. Importantly, the survival of the E. coli strains was dramatically increased by persistence in the C. elegans gut under 0.1% sodium hypochlorite, and several strains could survive at a concentration of 0.5%. In addition, all pathogenic E. coli strains in the C. elegans gut survived on the lettuce for 5 days even though they were washed with 0.1% sodium hypochlorite. Taken together, our results indicate that pathogenic E. coli ingested by C. elegans may be protected against washing treatment with commercial sanitizers on raw food materials.

The Nocardia sp. L-417 strain grown with n-hexadecane as a carbon source produced two types of biosurfactant that have different characteristics. These biosurfactants were purified by procedures that included ammonium sulphate fractionation, chilled acetone and hexane treatments, silica-gel column chromatography and Sephadex LH-20 gel filtration. The purified biosurfactants were very stable over a broad range of pHs (2-12) and temperatures (100 degrees C, 3 h). The biosurfactant type I had strong properties as an emulsifying agent and as an emulsion-stabilizing agent, whereas type II had a strong ability to reduce surface tension.