Teagasc Food Research Centre, Moorepark, Fermoy, Co Cork, Ireland.
Int J Food Microbiol. 2011 Mar 1;145 Suppl 1:S39-45. doi: 10.1016/j.ijfoodmicro.2010.10.012. Epub 2010 Oct 21.
Sixteen cheesemaking facilities were sampled during the production season at monthly intervals over a two-year period. Thirteen facilities were found to have samples positive for Listeria monocytogenes. Samples were divided into 4 categories; cheese, raw milk, processing environment and external to the processing environment (samples from the farm such as silage, bedding, and pooled water). In order to attempt to identify the source, persistence and putative transfer routes of contamination with the L. monocytogenes isolates, they were differentiated using PFGE and serotyping. Of the 250 isolates, there were 52 different pulsotypes. No pulsotype was found at more than one facility. Two facilities had persistent pulsotypes that were isolated on sampling occasions at least 6 months apart. Of the samples tested, 6.3% of milk, 13.1% of processing environment and 12.3% of samples external to the processing environment, respectively, were positive for L. monocytogenes. Pulsotypes found in raw milk were also found in the processing environment, however, one of the pulsotypes from raw milk was found in cheese on only one occasion. One of the pulsotypes isolated from the environment external to the processing facility was found on the surface of cheese, however, a number of them were found in the processing environment. The results suggest that the farm environment external to the processing environment may in some cases be the source of processing environment contamination with L. monocytogenes.
在两年的生产季节中，每月间隔一次对 16 个奶酪制作设施进行采样。发现 13 个设施的样本中存在单核细胞增生李斯特菌阳性。样本分为 4 类：奶酪、生奶、加工环境和加工环境外部（来自农场的样本，如青贮饲料、床上用品和 pooled water）。为了尝试确定 L. monocytogenes 分离株的污染来源、持久性和潜在传播途径，使用 PFGE 和血清分型对它们进行了区分。在 250 个分离株中，有 52 个不同的脉冲型。没有一个脉冲型出现在一个以上的设施中。有两个设施存在持久性脉冲型，它们在至少相隔 6 个月的采样时被分离。在所测试的样本中，分别有 6.3%的牛奶、13.1%的加工环境和 12.3%的加工环境外部样本对单核细胞增生李斯特菌呈阳性。在生奶中发现的脉冲型也存在于加工环境中，但生奶中的一个脉冲型仅在一次奶酪中发现。从加工环境外部环境中分离出的一个脉冲型在奶酪表面发现，但有许多在加工环境中发现。结果表明，加工环境外部的农场环境在某些情况下可能是加工环境中单核细胞增生李斯特菌污染的来源。
