Department of Food Hygiene and Technology, Universidad de León, León, Spain.
Department of Food Hygiene and Technology, Universidad de León, León, Spain; Institute of Food Science and Technology, Universidad de León, León, Spain.
Int J Food Microbiol. 2021 Feb 16;340:109043. doi: 10.1016/j.ijfoodmicro.2021.109043. Epub 2021 Jan 4.
The food processing environments of a newly opened meat processing facility were sampled in ten visits carried out during its first 1.5 years of activity and analyzed for the presence of Listeria monocytogenes. A total of 18 L. monocytogenes isolates were obtained from 229 samples, and their genomes were sequenced to perform comparative genomic analyses. An increase in the frequency of isolation of L. monocytogenes and in the diversity of sequence types (STs) detected was observed along time. Although the strains isolated belonged to six different STs (ST8, ST9, ST14, ST37, ST121 and ST155), ST9 was the most abundant (8 out of 18 strains). Low (0 and 2) single nucleotide polymorphism (SNP) distances were found between two pairs of ST9 strains isolated in both cases 3 months apart from the same processing room (Lm-1267 and Lm-1705, with a 2 SNPs distance in the core genome; Lm-1265 and Lm-1706, with a 0 SNPs distance), which suggests that these strains may be persistent L. monocytogenes strains in the food processing environment. Most strains showed an in silico attenuated virulence potential either through the truncation of InlA (in 67% of the isolates) or the absence of other virulence factors involved in cell adhesion or invasion. Twelve of the eighteen L. monocytogenes isolates contained a plasmid, which ranged in size from 4 to 87 Kb and harbored stress survival, in addition to heavy metals and biocides resistance determinants. Identical or highly similar plasmids were identified for various sets of L. monocytogenes ST9 isolates, which suggests the clonal expansion and persistence of plasmid-containing ST9 strains in the processing environments of the meat facility. Finally, the analysis of the L. monocytogenes genomes available in the NCBI database, and their associated metadata, evidenced that strains from ST9 are more frequently reported in Europe, linked to foods, particularly to meat and pork products, and less represented among clinical isolates than other L. monocytogenes STs. It also showed that the ST9 strains here isolated were more closely related to the European isolates, which clustered together and separated from ST9 North American isolates.
在一家新开业的肉类加工厂开业后的头 1.5 年内进行了 10 次采样，对其食品加工环境进行了检测，以确定李斯特菌的存在。从 229 个样本中获得了总共 18 个李斯特菌分离株，并对其基因组进行了测序，以进行比较基因组分析。随着时间的推移，李斯特菌的分离频率和序列型（ST）的多样性都有所增加。尽管分离出的菌株属于六个不同的 ST（ST8、ST9、ST14、ST37、ST121 和 ST155），但 ST9 是最丰富的（18 株中有 8 株）。在相隔 3 个月的同一加工室（Lm-1267 和 Lm-1705，核心基因组中有 2 个 SNP 差异；Lm-1265 和 Lm-1706，0 SNPs 差异）中分离出的两对 ST9 菌株之间发现 SNP 差异较小（0 和 2），这表明这些菌株可能是食品加工环境中持续存在的李斯特菌。大多数菌株的侵袭性毒力在体外均有所减弱，要么是由于 InlA 的截断（在 67%的分离株中），要么是由于其他与细胞黏附和入侵相关的毒力因子缺失。在 18 个李斯特菌分离株中，有 12 个含有质粒，大小从 4 到 87 Kb 不等，除了耐重金属和杀菌剂的决定子外，还含有应激生存决定子。不同 ST9 李斯特菌分离株的质粒完全相同或高度相似，这表明含有质粒的 ST9 菌株在肉类加工厂的加工环境中呈克隆性扩张和持续存在。最后，对 NCBI 数据库中可获得的李斯特菌基因组及其相关元数据进行分析，结果表明，ST9 菌株在欧洲更为常见，与食品有关，特别是与肉类和猪肉产品有关，而在临床分离株中比其他李斯特菌 ST 更为少见。结果还表明，这里分离的 ST9 菌株与欧洲分离株更为密切相关，这些菌株聚集在一起，与北美 ST9 分离株分离。
