De Cesare Alessandra, Mioni Renzo, Manfreda Gerardo
Department of Food Science, Alma Mater Studiorum-University of Bologna, Via S. Giacomo 9, 40126 Bologna, Italy.
Int J Food Microbiol. 2007 Nov 30;120(1-2):124-30. doi: 10.1016/j.ijfoodmicro.2007.06.009. Epub 2007 Jun 13.
Listeria monocytogenes has been detected in fresh as well as dry and semidry fermented sausages, rendering preparation and consumption of these products as a potential risk to human health. The aims of this study were (1) to evaluate the L. monocytogenes prevalence in 288 fresh and 237 fermented sausages produced in northern Italy; (2) to quantify the average pathogen Most Probable Number (MPN) per g of sausage; (3) to evaluate the sausage strain genetic diversity by automated PvuII ribotyping; and (4) to predict the pathogenicity lineage of these isolates determining their DuPont Identification Library Codes (DUP-IDs) by EcoRI ribotyping. The overall prevalence of L. monocytogenes in the sampled sausages was 28.2%. The percentage of L. monocytogenes positive fresh sausages was significantly higher than that of fermented sausages (i.e. 38.9 vs 15.2%), which had a pathogen load always lower than 10 MPN/g. In contrast, 16.1% of fresh sausages were contaminated by 10 to 100 MPN/g and 20.5% had more than 100 MPN/g. PvuII successfully discriminated sausage isolates with a Simpson's numerical index of discrimination of 0.637. A total of 12 and 9 different PvuII ribogroups were identified among 47 fresh and 24 fermented randomly selected sausage strains, respectively. Six of those ribogroups were shared between strains contaminating both kinds of sausages. According to the evaluation of the strain DUP-IDs, the majority of the isolates investigated in this study were part of the type II L. monocytogenes pathogenicity lineage, but type I lineage strains were identified among fermented sausage isolates. In conclusion, L. monocytogenes prevalence in Italian sausages was estimated to be around 28.2%. However, 84.2% of the samples were contaminated by less than 100 MPN of L. monocytogenes per g and the majority of L. monocytogenes contaminating strains would be classified in the type II pathogenicity lineage, including serotypes 1/2a, 1/2c and 3a.
在新鲜以及干制和半干制发酵香肠中均检测到了单核细胞增生李斯特菌，这使得这些产品的制备和食用对人类健康构成潜在风险。本研究的目的是：（1）评估意大利北部生产的288份新鲜香肠和237份发酵香肠中单核细胞增生李斯特菌的流行情况；（2）量化每克香肠中病原体的平均最可能数（MPN）；（3）通过自动化PvuII核糖体分型评估香肠菌株的遗传多样性；（4）通过EcoRI核糖体分型确定这些分离株的杜邦鉴定文库编码（DUP-IDs），以预测这些分离株的致病谱系。采样香肠中单核细胞增生李斯特菌的总体流行率为28.2%。单核细胞增生李斯特菌阳性新鲜香肠的百分比显著高于发酵香肠（即38.9%对15.2%），发酵香肠的病原体载量始终低于10 MPN/g。相比之下，16.1%的新鲜香肠被10至100 MPN/g的病原体污染，20.5%的新鲜香肠被污染程度超过100 MPN/g。PvuII成功区分了香肠分离株，辛普森鉴别数值指数为0.637。在随机选择的47份新鲜香肠菌株和24份发酵香肠菌株中，分别鉴定出12种和9种不同的PvuII核糖体组。其中有6种核糖体组在污染两种香肠的菌株中共有。根据对菌株DUP-IDs的评估，本研究中调查的大多数分离株属于II型单核细胞增生李斯特菌致病谱系，但在发酵香肠分离株中鉴定出了I型谱系菌株。总之，意大利香肠中单核细胞增生李斯特菌的流行率估计约为28.2%。然而，84.2%的样本每克被污染的单核细胞增生李斯特菌低于100 MPN，且大多数污染单核细胞增生李斯特菌的菌株将被归类为II型致病谱系，包括血清型1/2a、1/2c和3a。
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