Potential Enterotoxicity of Phylogenetically Diverse Bacillus cereus Sensu Lato Soil Isolates from Different Geographical Locations

Abstract

<i>Bacillus cereus sensu lato</i> comprises Gram-positive spore-forming bacteria producing toxins associated with foodborne diseases. Three pore-forming enterotoxins, nonhemolytic enterotoxin (Nhe), hemolysin BL (Hbl), and cytotoxin K (CytK), are considered the primary factors in <i>B. cereus sensu lato</i> diarrhea. The aim of this study was to determine the potential risk of enterotoxicity among soil <i>B. cereus sensu lato</i> isolates representing diverse phylogroups and originated from different geographic locations with various climates (Burkina Faso, Kenya, Argentina, Kazakhstan, and Poland). While <i>nheA</i>- and <i>hblA</i>-positive isolates were present among all <i>B. cereus sensu lato</i> populations and distributed across all phylogenetic groups, <i>cytK-2</i>-positive strains predominated in geographic regions with an arid hot climate (Africa) and clustered together on a phylogenetic tree mainly within mesophilic groups III and IV. The highest <i>in vitro</i> cytotoxicity to Caco-2 and HeLa cells was demonstrated by the strains clustered within phylogroups II and IV. Overall, our results suggest that <i>B. cereus sensu lato</i> pathogenicity is a comprehensive process conditioned by many intracellular factors and diverse environmental conditions.<b>IMPORTANCE</b> This research offers a new route for a wider understanding of the dependency between pathogenicity and phylogeny of a natural bacterial population, specifically within <i>Bacillus cereus sensu lato</i>, that is widely distributed around the world and easily transferred into food products. Our study indicates differences in the phylogenetic and geographical distributions of potential enterotoxigenic <i>B. cereus sensu lato</i> strains. Hence, these bacilli possess a risk for human health, and rapid testing methods for their identification are greatly needed. In particular, the detection of the CytK enterotoxin should be a supporting strategy for the identification of pathogenic <i>B. cereus sensu lato</i>.