Diversity of Listeria monocytogenes Strains of Clinical and Food Chain Origins in Belgium between 1985 and 2014

Listeriosis is a rare but severe disease, mainly caused by Listeria monocytogenes. This study shows the results of the laboratory-based surveillance of Listeriosis in Belgium over the period 1985–2014. Besides the incidence and some demographic data we present also more detailed microbiological and molecular characteristics of human strains isolated since 2000. The strains from the latter period were compared to food and animal strains from the same period. Our study shows that different food matrices were commonly contaminated with L. monocytogenes presenting the same PFGE profile as in patient’s isolates. Since 1985, we observed a significant decrease in incidence of the Materno-Neonatal cases (from 0.15 to 0.04 cases /100,000 inhabitants-year), which is probably to be attributed to active prevention campaigns targeting pregnant women. Despite the strengthening of different control measures by the food industry, the incidence of non-Materno-Neonatal listeriosis increased in Belgium (from 0.3 to 0.7 cases /100,000 inhabitants-year), probably due to the rise of highly susceptible patients in an aging population. This significant increase found in non-Materno-Neonatal cases (slope coefficient 7.42%/year, PL. monocytogenes isolates, a trend to increasing MIC values is evident with chloramphenicol, amoxicillin, tetracycline and ciprofloxacin. We show that fluoroquinolone resistance is not linked to chromosomal mutations, but caused by a variety of efflux pumps. Our study also shows that huge majority of known underlying pathologies (426 out of 785 cases) were cancers (185/426, 43.1%) and haematological malignancies (75/185, 40.5%). Moreover the risk population is susceptible to low levels of contamination in food stressing the need of prevention campaigns specifically targeting these persons.

李斯特菌病（Listeriosis）是一种罕见但病情危重的疾病，主要致病原为单核细胞增多性李斯特菌（Listeria monocytogenes）。本研究呈现了1985年至2014年间比利时基于实验室的李斯特菌病监测结果。除发病率与部分人口统计学数据外，我们还展示了2000年以来分离的人类菌株更细致的微生物学与分子生物学特征，并将该时期的菌株与同期食品及动物来源菌株进行了比对。
研究发现，多种食品基质普遍受到单核细胞增多性李斯特菌污染，其脉冲场凝胶电泳（PFGE）图谱与患者分离株的图谱一致。自1985年起，我们观察到孕产妇-新生儿型（Materno-Neonatal）李斯特菌病的发病率显著下降（从0.15例/10万人口·年降至0.04例/10万人口·年），这一现象或可归因于针对孕妇的主动预防宣教活动。尽管食品行业强化了多项防控措施，但比利时非孕产妇-新生儿型李斯特菌病的发病率仍呈上升趋势（从0.3例/10万人口·年升至0.7例/10万人口·年），这可能与人口老龄化背景下易感高危患者数量增加有关。非孕产妇-新生儿型病例的增幅显著（斜率系数为7.42%/年）；在单核细胞增多性李斯特菌分离株中，氯霉素、阿莫西林、四环素及环丙沙星的最低抑菌浓度（MIC）值均呈升高趋势。
研究表明，氟喹诺酮类（fluoroquinolone）耐药性并非由染色体突变介导，而是由多种外排泵（efflux pumps）所导致。本研究同时显示，在785例存在明确基础疾病的病例中，绝大多数为恶性肿瘤（共426例）；其中185例（占恶性肿瘤病例的43.1%）为血液系统恶性肿瘤，而该185例血液系统恶性肿瘤患者中，75例（占比40.5%）。此外，易感高危人群易受食品中低水平李斯特菌污染的影响，这凸显了针对该类人群开展专项预防宣教的必要性。