Hadjilouka Agni, Mantzourani Kyriaki-Sofia, Katsarou Anastasia, Cavaiuolo Marina, Ferrante Antonio, Paramithiotis Spiros, Mataragas Marios, Drosinos Eleftherios H
Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, GR-118 55 Athens, Greece.
Department of Agricultural and Environmental Sciences, Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy.
J Food Prot. 2015 Feb;78(2):311-22. doi: 10.4315/0362-028X.JFP-14-261.
The aims of the present study were to determine the prevalence and levels of Listeria monocytogenes and Escherichia coli O157:H7 in rocket and cucumber samples by deterministic (estimation of a single value) and stochastic (estimation of a range of values) approaches. In parallel, the chromogenic media commonly used for the recovery of these microorganisms were evaluated and compared, and the efficiency of an enzyme-linked immunosorbent assay (ELISA)-based protocol was validated. L. monocytogenes and E. coli O157:H7 were detected and enumerated using agar Listeria according to Ottaviani and Agosti plus RAPID' L. mono medium and Fluorocult plus sorbitol MacConkey medium with cefixime and tellurite in parallel, respectively. Identity was confirmed with biochemical and molecular tests and the ELISA. Performance indices of the media and the prevalence of both pathogens were estimated using Bayesian inference. In rocket, prevalence of both L. monocytogenes and E. coli O157:H7 was estimated at 7% (7 of 100 samples). In cucumber, prevalence was 6% (6 of 100 samples) and 3% (3 of 100 samples) for L. monocytogenes and E. coli O157:H7, respectively. The levels derived from the presence-absence data using Bayesian modeling were estimated at 0.12 CFU/25 g (0.06 to 0.20) and 0.09 CFU/25 g (0.04 to 0.170) for L. monocytogenes in rocket and cucumber samples, respectively. The corresponding values for E. coli O157:H7 were 0.59 CFU/25 g (0.43 to 0.78) and 1.78 CFU/25 g (1.38 to 2.24), respectively. The sensitivity and specificity of the culture media differed for rocket and cucumber samples. The ELISA technique had a high level of cross-reactivity. Parallel testing with at least two culture media was required to achieve a reliable result for L. monocytogenes or E. coli O157:H7 prevalence in rocket and cucumber samples.
本研究的目的是通过确定性方法（估计单个值）和随机方法（估计一系列值）来确定火箭生菜和黄瓜样本中单核细胞增生李斯特菌和大肠杆菌O157:H7的流行率和水平。同时，对常用于这些微生物复苏的显色培养基进行了评估和比较，并验证了基于酶联免疫吸附测定（ELISA）方案的效率。分别使用根据奥塔维亚尼和阿戈斯蒂方法改良的李斯特菌琼脂培养基加RAPID'L. mono培养基以及含头孢克肟和亚碲酸盐的荧光培养基加山梨醇麦康凯培养基，同时对单核细胞增生李斯特菌和大肠杆菌O157:H7进行检测和计数。通过生化和分子检测以及ELISA确认其特性。使用贝叶斯推理估计培养基的性能指标和两种病原体的流行率。在火箭生菜中，单核细胞增生李斯特菌和大肠杆菌O157:H7的流行率估计均为7%（100个样本中有7个）。在黄瓜中，单核细胞增生李斯特菌和大肠杆菌O157:H7的流行率分别为6%（100个样本中有6个）和3%（100个样本中有3个）。使用贝叶斯模型从存在-不存在数据得出的水平估计，火箭生菜样本中单核细胞增生李斯特菌为0.12 CFU/25 g（0.06至0.20），黄瓜样本中为0.09 CFU/25 g（0.04至0.170）。大肠杆菌O157:H7的相应值分别为0.59 CFU/25 g（0.43至0.78）和1.78 CFU/25 g（1.38至2.24）。火箭生菜和黄瓜样本中培养基的敏感性和特异性有所不同。ELISA技术具有较高的交叉反应性。需要至少两种培养基进行平行检测，才能获得火箭生菜和黄瓜样本中单核细胞增生李斯特菌或大肠杆菌O157:H7流行率的可靠结果。
