Isolation and characterization of bacillus cereus strains isolated from a beef pizza food poisoning incident in Hanoi

Bacillus cereus is one of the global causes of food poisoning. In this study, we isolated 10 strains of B. cereus from beef pizza samples identified as the cause of food poisoning among students at two kindergartens A and B in Vietnam in 2024.

Species identification was carried out using biochemical tests and MALDI-TOF technology; antibiotic resistance profile was constructed according to the M45 CLSI guidelines, and examined the presence of cytK, bceT, hbl (hblA, hblC, and hblD) and nhe (nheA, nheB, and nheC) toxin genes among these isolated strains. The antibiotic resistance testing results showed that isolated B. cereus strains were significantly resistant to several strong antibiotics, including penicillin (100 %), vancomycin (100 %), strepto-mycin (90 %), tetracycline (80 %), ampicillin (70 %), and erythomycin (70 %). In addition, 100 % of B. cereus strains (10/10) in the beef pizza sample were positive for the bceT toxin gene, 80 % of strains (8/10) were positive for the cytK toxin gene, and 60% of strains (6/10) were positive for the nheA and nheC toxin genes, and negative for the NRPS emetic toxin gene. Our study contributes to the antibiotic resistance database for B. cereus associated with food poisoning in Vietnam and provides a valuable resource for developing reference materials aimed at the rapid diagnosis of food poisoning caused by diarrhea B. cereus type.