Dairy plant contamination by Bacillus cereus. Virulence genes and cross-contamination by Bacillus cereus sensu lato isolated from processing equipment of an Algerian dairy plant

the panC gene clustered them in phylogenetic group III (64.7%) and group IV (35.3%). The results of PFGE showed that 8 (47.1%), 4 (23.5%), 3 (17.6%) and 2 (11.8%) were differentiated into four groups A, B, C and D, respectively. Each of the two panC phylogenetic groups contain two different types of isolates corresponding to PFGE group (A and C) and (B and D) for phylogenetic group III and IV, respectively. None of the 14 isolates carried the emetic toxin (ces) gene whereas other toxin genes sph, nheA, nheB, nheC, hblC, plcA, entT, entFM, entS and cytK, were detected in 88.2%, 88.2%, 94.1%, 94.1%, 29.4%, 94.1%, 35.3 %, 100 %, 100 % and 41.2 %, respectively of isolated strains. Population structure analysis using hierarchical clustering of the core genome alignment showed five distinct sequence clusters encompassing all the sequences that could not be classified with confidence by hierBAPS. The isolates were assigned to 3 different sequence types (ST 2226, ST1018 and ST1431) and one clonal complex (CC-142) identified in 3 isolates. Out of 12 sequenced B. cereus isolates, 3 (25%) contained three enterotoxic HBL complex encoding genes hblA/C/D. All three enterotoxic NHE complex encoding genes (nheA/B/C) and the ctyK1 gene were detected in all isolates. High numbers of B. cereus result in food poisoning due to the presence of toxins and their subsequent production of toxins, presenting a potential risk to the consumer. The overall results highlighting the risk due to toxins production by B. cereus group in food and the consequences for food safety and dairy industries in Algeria. The present study will help to better assess the health and spoilage risk associated with B. cereus in dairy processing plants in Algeria and to incorporate adequate preventive measures. This study emphasized the potential of whole-genome sequencing for genotyping and to predict the virulence associated genes and antimicrobial resistance with a high degree of accuracy.