Listeria monocytogenes contamination in raw pork and ready to eat foods is an important food safety concern, also for the increasing detection of antimicrobial-resistant isolates. Data on L. monocytogenes occurrence, persistence, distribution and genetic characterization in two different plants, namely in continuum from slaughtered pigs, environment and unfinished products (fresh hams) were observed by one-year monitoring and were integrated with their antimicrobial resistance patterns. A total of 98 samples out of the overall 1131 (8.7%) were positive for L. monocytogenes, respectively 2.6% and 13.2% in plants A and B: only three serotypes were identified, 1/2c (50%), 1/2b (36.7%) and 1/2a (13.27%), and strains were classified in 35 pulsotypes and 16 clusters by PFGE; a unique P-type was highlighted according to the detection of virulence genes. The contamination flow of L. monocytogenes has a low occurrence in slaughterhouse (Plant A = 1.1%, Plant B: 3.1%; p > 0.05) and increased throughout the processing chain with trimming area as the most contaminated (Plant A: 25%, Plant B: 57%; (p < 0.05)), both in the environment and in unfinished products (80% in hams before trimming in plant B). The dominant role of environmental contamination in post-slaughter processing is confirmed to be a significant cause of meat contamination by L. monocytogenes. Very high levels of resistance were observed for clindamycin (57%) and high resistance levels (>20–50%) to ciprofloxacin, oxacillin, levofloxacin and daptomycin, confirming the L. monocytogenes resistance trend to a wide range of antimicrobial agents. A total of 11 L. monocytogenes isolates were multidrug resistant and 7 out of them were isolated from slaughtered pigs. An interesting significant (p < 0.05) statistical correlation has been found between resistance to some antimicrobial agents and lineage/serotypes. Microbiological sampling of food and environments after sanitization are commonly used as verification procedure for the absence of L. monocytogenes in food plants and to give assurance of food safety, but strains characterization is necessary for industries to target specific control measures, like the enforcement of the hygiene program and of the control of operator activities, at least for permanent strains. The only presence of L. monocytogenes could not be considered as the conclusive assessment of a potential risk for public health, also in terms of emerging and emerged antimicrobial resistances.

生猪肉和即食食品中的单核细胞增生性李斯特菌污染是重要的食品安全问题，对于增加对抗菌素耐药菌株的检测也是如此。通过一年的监测，观察了两种不同植物（即来自屠宰猪的连续体）中单核细胞增生李斯特菌的发生，持久性，分布和遗传特征的数据，并通过一年的监测对其进行了观察，并将其与抗菌素耐药性模式进行了整合。总共1131个样本中有98个样本（8.7％）对单核细胞增生李斯特菌呈阳性分别在植物A和B中分别为2.6％和13.2％：仅鉴定出三种血清型，分别为1 / 2c（50％），1 / 2b（36.7％）和1 / 2a（13.27％），菌株被分类为35种脉冲型PFGE的16个集群；根据毒力基因的检测，一种独特的P型突出显示。单核细胞增生李斯特氏菌的污染流在屠宰场中的发生率较低（植物A = 1.1％，植物B：3.1％；p  > 0.05），并且在整个加工链中呈上升趋势，修剪区域污染最严重（植物A：25％，植物B：57％;（p <0.05）），无论是在环境中还是在未完成的产品中（在工厂B修剪前以火腿为80％）。确认环境污染在屠宰后加工中的主要作用是造成单核细胞增生李斯特氏菌污染肉类的重要原因。克林霉素的耐药水平很高（57％），对环丙沙星，奥沙西林，左氧氟沙星和达托霉素的耐药水平很高（> 20–50％），这证实了单核细胞增生李斯特氏菌对多种抗菌药物的耐药性趋势。共有11种 单核细胞增生李斯特氏菌分离株具有多药耐药性，其中7种是从屠宰猪中分离出来的。一个有趣的意义（p <0.05）在对某些抗菌剂的耐药性与谱系/血清型之间发现了统计相关性。消毒后对食品和环境进行微生物采样通常用作验证程序，以确认食品中是否存在单核细胞增生李斯特菌，并保证食品安全，但是菌株表征对于行业针对特定的控制措施（如强制实施食品安全管理）是必要的。卫生计划和操作员活动的控制，至少对于永久性劳损而言。单核细胞增生李斯特氏菌的唯一存在不能被视为对公共健康潜在风险的结论性评估，就新出现和出现的抗菌素耐药性而言也是如此。