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Outline
To explore the contamination level, carrier status of drug resistance genes and virulence genes of strains and molecular characteristics of Bacillus cereus in food products in Tongchuan City from 2023 to 2025.
This study conducted a quantitative analysis of Bacillus cereus contamination levels in commercially ava ilable food products in Tongchuan City from 2023 to 2025. Whole-genome sequencing was performed on 51 foodborne Bacillus cereus isolates following identification. The sequencing data were utilized for multilocus sequence typing (MLST), analysis of virulence gene and antimicrobial resistance gene carriage, and phylogenetic reconstruction based on single nucleotide polymorphism profiling.
Between 2023 and 2025, a total of 51 strains of Bacillus cereus were isolated from 384 commercial food samples across 11 categories in Tongchuan City, yielding an overall detection rate of 13.28%. The contamination levels ranged from 10 to 103 CFU/g.Among the 51 foodborne Bacillus cereus strains, 43 distinct sequence types (ST) were identified. Among them,ST1667 (4 strains), ST22 (3 strains), ST1310 (2 strains), ST100 (2 strains) and ST1786 (2 strains), and the remaining types were represented by only one strain each. The virulence gene profiles of the isolates revealed 5 kinds of distinct patterns. Pattern II (comprising BAS3109, cytK, hblA, hblC, hblD, inhA, nheA, nheB, nheC) was the most prevalent,accounting for 58.80% of the strains. The carrying rate of non-hemolytic enterotoxin virulence genes nheABC in the 51 foodborne Bacillus cereus strains was 100.00%, the carrying rate of hemolysin virulence genes hblACD was 68.63%, and the carrying rate of cytotoxin virulence genes cytK was 82.35%. One isolate carried the emetic toxin gene cesB, concurrently harboring diarrheal enterotoxin genes. The strains exhibited varying degrees of antimicrobial resistance gene carriage, including blaZ, fosB1, tet(45), fosB and fosX, with an overall resistance gene prevalence of 60.78%. Evolutionary analysis revealed that the 51 foodborne Bacillus cereus isolates were classified into 3 major evolutionary clades. Among them, the 4 strains of ST1667, 3 strains of ST1310 and 2 strains of ST22 exhibited high intra-type homogeneity within their respective sequence types.
The contamination level of Bacillus cereus in Tongchuan City from 2023 to 2025 is relatively low; however, the carriage rate of diarrheal enterotoxin virulence genes is exceptionally high. Moreover, ready-to-eat foods constitute a significant proportion of the sources.These findings indicate that the risk associated with foodborne Bacillus cereus cannot be overlooked and warrants further investigation and attention.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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