Stea Emma C, Purdue Laura M, Jamieson Rob C, Yost Chris K, Truelstrup Hansen Lisbeth
Department of Process Engineering and Applied Science, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Biology, University of Regina, Regina, Saskatchewan, Canada.
Appl Environ Microbiol. 2015 Jun;81(11):3812-22. doi: 10.1128/AEM.00416-15. Epub 2015 Mar 27.
Foods and related processing environments are commonly contaminated with the pathogenic Listeria monocytogenes. To investigate potential environmental reservoirs of Listeria spp. and L. monocytogenes, surface water and point source pollution samples from an urban and a rural municipal water supply watershed in Nova Scotia, Canada, were examined over 18 months. Presumptive Listeria spp. were cultured from 72 and 35% of rural and urban water samples, respectively, with 24% of the positive samples containing two or three different Listeria spp. The L. innocua (56%) and L. welshimeri (43%) groups were predominant in the rural and urban watersheds, respectively. Analysis by the TaqMan assay showed a significantly (P < 0.05) higher prevalence of L. monocytogenes of 62% versus 17% by the culture-based method. Both methods revealed higher prevalences in the rural watershed and during the fall and winter seasons. Elevated Escherichia coli (≥ 100 CFU/100 ml) levels were not associated with the pathogen regardless of the detection method. Isolation of Listeria spp. were associated with 70 times higher odds of isolating L. monocytogenes (odds ratio = 70; P < 0.001). Serogroup IIa was predominant (67.7%) among the 285 L. monocytogenes isolates, followed by IVb (16.1%), IIb (15.8%), and IIc (0.4%). L. monocytogenes was detected in cow feces and raw sewage but not in septic tank samples. Pulsotyping of representative water (n = 54) and local human (n = 19) isolates suggested genetic similarities among some environmental and human L. monocytogenes isolates. In conclusion, temperate surface waters contain a diverse Listeria species population and could be a potential reservoir for L. monocytogenes, especially in rural agricultural watersheds.
食品及相关加工环境通常会被致病性单核细胞增生李斯特菌污染。为了调查李斯特菌属和单核细胞增生李斯特菌的潜在环境储存库，对加拿大新斯科舍省一个城市和一个农村市政供水流域的地表水和点源污染样本进行了为期18个月的检测。分别从72%的农村水样和35%的城市水样中培养出疑似李斯特菌属，其中24%的阳性样本含有两种或三种不同的李斯特菌属。无害李斯特菌组（56%）和威氏李斯特菌组（43%）分别在农村和城市流域中占主导地位。TaqMan检测分析显示，单核细胞增生李斯特菌的患病率显著高于基于培养法的患病率（P < 0.05），分别为62%和17%。两种方法均显示农村流域以及秋冬季节的患病率较高。无论采用何种检测方法，大肠杆菌水平升高（≥ 100 CFU/100 ml）与该病原体均无关联。分离出李斯特菌属的样本中，分离出单核细胞增生李斯特菌的几率高出70倍（优势比 = 70；P < 0.001）。在285株单核细胞增生李斯特菌分离株中，血清群IIa占主导地位（67.7%），其次是IVb（16.1%）、IIb（15.8%）和IIc（0.4%）。在牛粪和未经处理的污水中检测到了单核细胞增生李斯特菌，但在化粪池样本中未检测到。对代表性水样（n = 54）和当地人类样本（n = 19）分离株进行脉冲场凝胶电泳分型表明，一些环境和人类单核细胞增生李斯特菌分离株之间存在遗传相似性。总之，温带地表水含有多种李斯特菌属，可能是单核细胞增生李斯特菌的潜在储存库，尤其是在农村农业流域。
