Bacillus cereus sensu lato (B. cereus s.l.) comprises gram-positive spore-forming bacteria producing toxins associated with foodborne diseases. Three pore-forming enterotoxins, non-haemolytic enterotoxin (Nhe), haemolysin BL (Hbl), and cytotoxin K (CytK), are considered as the primary factors in B. cereus s.l. diarrhoea. The aim of this study was to determine the potential risk of enterotoxicity among soil B. cereus s.l. isolates representing various phylogroups and originated from different geographic locations varying in climate (Burkina Faso, Kenya, Argentina, Kazakhstan, and Poland). While, the nheA- and hblA-positive isolates are present among all B. cereus s.l. populations and distributed across all phylogenetic groups, the cytK-2-positive strains predominate in geographic regions with arid hot climate (Africa) and clustered together on a phylogenetic tree mainly within mesophilic groups III and IV. The highest in vitro cytotoxicity to Caco-2 and HeLa cells was demonstrated by the strains clustered within phylogroups II and IV. Overall, our results suggest that B. cereus s.l. pathogenicity is a comprehensive process conditioned by many intracellular factors and diverse environmental conditions.

IMPORTANCE This research offers a new route for a wider understanding of the dependency between pathogenicity and phylogeny of natural bacterial population, specifically within B. cereus s.l., that are widely distributed around the world and are easily transferred into food products. Our study indicates differences in the phylogenetic and geographical distribution of potential enterotoxigenic B. cereus s.l. strains. Hence these bacilli possess a risk for human health, rapid testing methods for their identification are greatly needed. Especially detection of the CytK enterotoxin should be a supporting strategy for the identification of pathogenic B. cereus s.l.

蜡状芽孢杆菌（B. cereus sl）包含革兰氏阳性孢子形成细菌，产生与食源性疾病相关的毒素。三种孔形成性肠毒素，即非溶血性肠毒素（Nhe），溶血素BL（Hbl）和细胞毒素K（CytK），被认为是蜡状芽孢杆菌腹泻的主要因素。这项研究的目的是确定代表不同种系并起源于气候不同地区（布基纳法索，肯尼亚，阿根廷，哈萨克斯坦和波兰）的蜡状芽孢杆菌（B. cereus sl）分离株之间肠毒性的潜在风险。而在所有蜡状芽孢杆菌中都存在nheA和hblA阳性分离株cytK-2阳性菌株分布在所有的系统发育族群中，在干旱热气候（非洲）的地理区域中占主导地位，并聚集在主要在中温性组III和IV中的系统发育树上。聚簇在系统群II和IV内的菌株证明了对Caco-2和HeLa细胞的最高体外细胞毒性。总体而言，我们的结果表明蜡状芽孢杆菌的致病性是一个受许多细胞内因素和各种环境条件制约的综合过程。

重要事项这项研究提供了一条新途径，可以更广泛地了解天然细菌种群的致病性和系统发育之间的依赖性，特别是在蜡状芽孢杆菌中，而蜡状芽孢杆菌在世界范围内分布广泛，很容易转移到食品中。我们的研究表明潜在的产肠毒素的蜡状芽孢杆菌sl菌株在系统发育和地理分布上的差异。因此，这些细菌具有危害人类健康的风险，非常需要快速的鉴定方法。特别是CytK肠毒素的检测应该是鉴定致病性蜡状芽孢杆菌sl的支持策略