Cheese potentially allowing the growth of Listeria monocytogenes must be free of the pathogen in 25 g before being put on the market, while 100 cfu/g is tolerated when the pathogen is unable to grow. Challenge tests were performed in order to assess the growth potential of L. monocytogenes in at least one batch of 32 Belgian cheese varieties from 32 factories. All varieties were grouped in four categories: unripened acid-curd cheeses, mold-ripened soft cheeses, smear-ripened soft cheeses and ripened semi-hard cheeses. Associated microflora and cheese physicochemical characteristics were also studied. A cocktail of three strains was used to inoculate cheese on the first day of shelf-life, and samples were stored until the end of shelf-life at 7–9 °C. Growth potential was considered as the difference (a) between median contamination at the end and at the beginning of the test or (b) between the highest value at the end of the test and the lowest value at its beginning. L. monocytogenes always decreased in unripened acid-curd cheeses but showed extended growth in 21 out of 25 batches of ripened soft cheese. Contrasting results were obtained for semi-hard cheeses, as important intra- and inter-batch variability was observed. For the latter, the recommended method based on medians to calculate the growth potential led to erroneous food safety considerations, and it should always be advised to focus on absolute levels.

可能允许单核细胞增生性李斯特菌生长的奶酪在投放市场之前，必须在25 g中不含病原体，而当病原体无法生长时，则允许100 cfu / g。进行了攻击试验，以评估单核细胞增生李斯特菌的生长潜力至少有32家工厂的32种比利时奶酪品种。所有品种均分为四类：未成熟的酸乳干酪，霉菌型软干酪，涂片型软干酪和成熟的半硬干酪。还研究了相关的菌群和奶酪的理化特性。在保质期的第一天，使用三种菌株的混合物接种奶酪，并在7–9°C下保存样品直至保质期结束。生长潜力被认为是（a）测试结束时和开始时的中值污染之间的差异，或（b）测试结束时的最高值与开始时的最低值之间的差。单核细胞增生李斯特菌在未熟化的酸奶酪中，总含量会下降，但在25批成熟的软奶酪中，有21剂的增长持续。由于观察到重要的批内和批间变异性，半硬质奶酪获得了相反的结果。对于后者，建议的基于中位数的计算增长潜力的方法会导致错误的食品安全考虑，因此应始终建议将注意力集中在绝对水平上。