Laboratory of Food Quality Control and Hygiene, Department of Food Science and Technology, Agricultural University of Athens, Iera Odos 75, Athens, Greece.
J Food Prot. 2012 Aug;75(8):1518-23. doi: 10.4315/0362-028X.JFP-11-556.
Listeria monocytogenes poses a serious threat to public health, and the majority of cases of human listeriosis are associated with contaminated food. Reliable microbiological testing is needed for effective control of this pathogen by the food industry and competent authorities. The aim of this study was to determine the performance of three culture media commonly used for detecting L. monocytogenes in foods. Minced pork meat samples (n = 100) were subjected to microbiological testing for L. monocytogenes according to International Organization for Standardization methods 11290-1:1996 and 11290-2:1998 using PALCAM, ALOA, and RAPID'L. mono culture media in parallel. Presence of the pathogen was confirmed by conducting biochemical and molecular tests on the presumptive L. monocytogenes colonies. Performance attributes of sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, diagnostic odds ratios, error odds ratios, receiving operating characteristic (ROC) curve, and area under this curve were calculated from the presence-absence microbiological test results by combining the results obtained from the culture media and confirmative tests. PALCAM had the best performance in terms of positive predictive value (i.e., a positive result indicates high probability of L. monocytogenes presence) but not in terms of sensitivity (i.e., the ability of the medium to detect the pathogen when present). RAPID'L. mono was the most sensitive medium. None of the culture media were perfect for detecting L. monocytogenes in minced pork meat alone. The pathogen was detected in 16, 19, and 26% (apparent prevalence) of the samples by PALCAM, ALOA, and RAPID'L. mono, respectively, although the true prevalence of the pathogen was 22%. These findings indicate that the use of a single culture medium may lead to erroneous determination of the prevalence of L. monocytogenes.
李斯特菌对公共健康构成严重威胁，大多数人类李斯特菌病病例与污染食物有关。食品行业和主管部门需要可靠的微生物检测来有效控制这种病原体。本研究旨在确定三种常用于检测食品中李斯特菌的培养基的性能。根据国际标准化组织方法 11290-1:1996 和 11290-2:1998，对 100 份绞碎猪肉样品进行李斯特菌微生物检测，同时使用 PALCAM、ALOA 和 RAPID'L. mono 培养基进行平行检测。通过对疑似李斯特菌菌落进行生化和分子检测，确认病原体的存在。通过对组合培养物和确认试验结果进行分析，从存在-不存在微生物检测结果中计算出灵敏度、特异性、阳性和阴性预测值、阳性和阴性似然比、诊断比值比、错误比值比、接收操作特性（ROC）曲线和曲线下面积等性能属性。PALCAM 在阳性预测值方面表现最好（即阳性结果表示李斯特菌存在的可能性很高），但在灵敏度方面表现不佳（即当存在时，培养基检测病原体的能力）。RAPID'L. mono 是最敏感的培养基。没有一种培养基能够单独检测绞碎猪肉中的李斯特菌。PALCAM、ALOA 和 RAPID'L. mono 分别在 16%、19%和 26%（表观流行率）的样本中检测到该病原体，尽管该病原体的真实流行率为 22%。这些发现表明，使用单一培养基可能导致李斯特菌流行率的错误确定。
