<sec><title>Objectives</title><p>To investigate the prevalence and toxin production characteristics of non-emetic and emetic <italic>Bacillus cereus</italic> strains isolated via the laboratory surveillance system in Korea.</p></sec><sec><title>Methods</title><p>A total of 667 <italic>B. cereus</italic> strains were collected by the Korea National Research Institute of Health laboratory surveillance system from 2012 to 2014. The collected strains were analyzed by geographical region, season, patient age, and patient sex. Additionally, the prevalence rates of enterotoxin and emetic toxin genes were evaluated.</p></sec><sec><title>Results</title><p>The isolation rate of <italic>B. cereus</italic> strains increased during the summer, but the isolation rate was evenly distributed among patient age groups. Emetic toxin was produced by 20.2% of the isolated strains. The prevalence rates of five enterotoxin genes (<italic>entFM</italic>, <italic>nheA</italic>, <italic>cytK2</italic>, <italic>hblC</italic>, and <italic>bceT</italic>) were 85.0, 78.6, 44.5, 36.6, and 29.7%, respectively, among non-emetic strains and 77.8, 59.3, 17.8, 11.9 and 12.6%, respectively, among emetic strains. Thus, the prevalence rates of all five enterotoxin genes were lower in emetic <italic>B. cereus</italic>.</p></sec><sec><title>Conclusion</title><p>The prevalence of enterotoxin genes differed between non-emetic and emetic <italic>B. cereus</italic> strains. Among emetic <italic>B. cereus</italic> strains, the prevalence rates of two enterotoxin genes (<italic>cytK2</italic> and <italic>hblC</italic>) were lower than those among the non-emetic strains. In both the emetic and non-emetic strains isolated in Korea, <italic>nheA</italic> and <italic>entFM</italic> were the most prevalent enterotoxin genes.</p></sec>

Objectives
We aimed at evaluating the virulence of atypical <i>Shigella flexneri</i> II:(3)4,7(8) by DNA microarray and invasion assay.
Methods
We used a customized <i>S. flexneri</i> DNA microarray to analyze an atypical <i>S. flexneri</i> II:(3)4,7(8) gene expression profile and compared it with that of the <i>S. flexneri</i> 2b strain.
Results
Approximately one-quarter of the atypical <i>S. flexneri</i> II:(3)4,7(8) strain genes showed significantly altered expression profiles; 344 genes were more than two-fold upregulated, and 442 genes were more than 0.5-fold downregulated. The upregulated genes were divided into the category of 21 clusters of orthologous groups (COGs), and the “not in COGs” category included 170 genes. This category had virulence plasmid genes, including the <i>ipa-mxi-spa</i> genes required for invasion of colorectal epithelium (type III secretion system). Quantitative reverse-transcription polymerase chain reaction results also showed the same pattern in two more atypical <i>S. flexneri</i> II:(3)4,7(8) strains. Atypical <i>S. flexneri</i> II:(3)4,7(8) showed four times increased invasion activity in Caco-2 cells than that of typical strains.
Conclusion
Our results provide the intracellularly regulated genes that may be important for adaptation and growth strategies of this atypical <i>S. flexneri</i>.