Intraspecific Diversity and Pathogenicity of Bacillus thuringiensis Isolates from an Emetic Illness.

This study describes an emetic food-borne intoxication associated with a group species and the characterization of the bacterial isolates from the incident in aspects of molecular tying, genetic factors, cytotoxicity, and pathogenic mechanisms relating to emetic illness. Through the polyphasic identification approach, all seven isolates obtained from food and clinical samples were identified as . According to multilocus sequence typing (MLST) analysis, intraspecific diversity was found within the isolates. Four allelic profiles were found, including two previously known STs (ST8 and ST15) and two new STs (ST2804 and ST2805). All isolates harbored gene fragments located in the () gene cluster. The heat-treated culture supernatants of three emetic isolates, FC2, FC7, and FC8, caused vacuolation and exhibited toxicity to Caco-2 cells, with CC values of 56.57, 72.17, and 79.94 µg/mL, respectively. The flow cytometry with the Annexin V/PI assay revealed both apoptosis and necrosis mechanisms, but necrosis was the prominent mechanism that caused Caco-2 cell destruction by FC2, the most toxic isolate.