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To analyze the contamination status of Listeria monocytogenes in the production and distribution stages of enoki mushrooms in Chengdu.
A total of 180 samples were collected from two major enoki mushroom manufacturers in Chengdu, including enoki mushrooms (30 samples), culture media (14 samples), environmental samples (25 samples), tools and equipment (64 samples), operators (30 samples), and other samples (17 samples). L.monocytogenes was isolated and identified according to the 2024 National Manual for Monitoring Food Contaminants and Harmful Factors. Whole-genome sequencing (WGS) was conducted on the isolates to predict serotypes and analyze lineages, sequence types (ST), clonal complexes (CC), antimicrobial resistance genes, and virulence genes. Homology among strains was determined based on core genome multilocus sequence typing (cgMLST) genetic characteristics.
A total of 69 L.monocytogenes strains were detected from 180 samples, with an overall detection rate of 38.33%. The strains belonged to two lineages (I and II), with lineage II being predominant (97.10%, 67/69). Three serotypes were identified, among which serotype 1/2a,3a was dominant (94.20%, 65/69). Seven CC types were detected, with CC8 (52.17%, 36/69) and CC155 (30.43%, 21/69) being dominant. Eight ST types were identified, among which ST8 (52.17%, 36/69) and ST155 (30.43%, 21/69) were the predominant types. All strains carried only the antimicrobial resistance gene fosX. All 69 strains carried virulence island 1 (LIPI-1), and six virulence genes (prfA, plcA, hly, mpl, actA, and plcB) were all positive. All 69 strains also carried virulence island 2 (LIPI-2); among the nine virulence genes, inlA, inlB, inlC, and inlJ were positive in all strains; inlE, inlG, and inlH were all negative; and the carriage rates of inlF and inlK were both 97.10% (67/69). CgMLST clustering analysis revealed the presence of homologous strains.
L.monocytogenes contamination is present in both the production and distribution stages of enoki mushrooms in Chengdu, with a potential for cross-contamination. Although current antimicrobial resistance is not severe, the strains harbor numerous virulence genes, suggesting potential for acquiring resistance genes and posing a threat to human health.
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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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