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 o 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).

Salmonella infections represent an important public health problem. In 2018, a multistate outbreak of S. enterica subsp. enterica serovar Thompson infection associated with contaminated chocolate cakes in schools was reported in South Korea. In this study, we sequenced the 37 S. Thompson strains isolated from chocolate cakes, egg whites, preserves, and cookware associated with the outbreak. In addition, we analyze the genomic sequences of 61 S. Thompson strains (37 chocolate cake-related outbreak strains, 4 strains isolated from outbreaks in South Korea and 20 strains available in the National Center for Biotechnology Information) to assess the genomic characteristics of outbreak-related strains by comparative genomics and phylogenetic analysis. The results showed that identically classified clusters divided strains into two clusters, sub-clusters A & I (with strains from 2018 in South Korea) and sub-clusters B & II (with strains from 2014 to 2015 in South Korea). S. Thompson isolated from South Korea were accurately distinguished from publicly-available strains. Unlike other S. Thompson genomes, those of chocolate cake outbreak-related strains had three Salmonella phages (SEN8, vB SosS Oslo, and SI7) integrated into their chromosome. Comparative genomics revealed several genes responsible for the specific genomic features of chocolate cake outbreak-related strains and three bacteriophages that may contribute to the pathogenicity of other S. Thompson strains.