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首页> 外文期刊>Food microbiology >Survival of Escherichia coli O157:H7 in Galotyri cheese stored at 4 and 12℃
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Survival of Escherichia coli O157:H7 in Galotyri cheese stored at 4 and 12℃

机译：大肠杆菌O157：H7在Galotyri奶酪中4和12℃下的存活率

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Post-process contamination of fresh acid-curd cheeses with Escherichia coli O157:H7 may pose a risk considering the low infectious dose and the ability of the pathogen to survive in acidic foods. To evaluate its survival in Galotyri, a traditional Greek acid-curd cheese, portions (0.5 kg) of two commercial fresh products, one artisan (pH 3.9 ± 0.1) and the other industrial (pH 3.7 ± 0.1), were inoculated with approximately 3.0 or 6.51og cfu g~(-1) of a five-strain cocktail of E. coli O157:H7, including rifampicin-resistant derivatives of the strains ATCC 43895 and ATCC 51657, and stored aerobically at 4 and 12℃. Survival was monitored for 28 days by plating cheese samples on tryptic soy agar with 100 mg l~(-1) rifampicin (TSA + Rif), SMAC and Fluorocult E. coli O157:H7 agar media. The pathogen declined much faster (P<0.05) in the industrial as compared to the artisan cheeses at both temperatures. Thus, while E. coli O157:H7 became undetectable by culture enrichment after 14 days at 4℃ in industrial samples, irrespective of the inoculation level, populations of 1.4-1.9 and 4.2-5.1 log cfu g~(-1) survived after 28 days in the corresponding artisan cheeses with the low and high inocula, respectively. Survival was longer and greater (P<0.05) on TSA + Rif than on SMAC and Fluorocult, indicating the presence of acid-injured cells. Interestingly, survival of E. coli O157:H7 after 14-28 days in cheeses was better at 12℃ than at 4℃, probably due to yeasts which grew on the surface of temperature-abused cheeses. The large difference in the pathogen's inactivation between the industrial and artisan cheeses at 4℃ could not be associated with major differences in pH or type/concentration of organic acids, suggesting another anti-E. coli O157:H7 activity by the industrial starter. The high survival of the pathogen in artisan Galotyri under conditions simulating commercial storage should be of concern.
机译：考虑到低的传染剂量和病原体在酸性食品中的生存能力，大肠杆菌O157：H7对新鲜酸凝奶酪的后处理污染可能会带来风险。为了评估其在Galotyri中的存活率，这是一种传统的希腊酸凝乳酪，将两份商业新鲜产品（一种工匠（pH 3.9±0.1）和另一种工业产品（pH 3.7±0.1））（0.5 kg）分别接种约3.0或6.51og cfu g〜（-1）的五株大肠杆菌O157：H7混合物，包括菌株ATCC 43895和ATCC 51657的耐利福平衍生物，需氧存储在4和12℃。通过将干酪样品涂在胰蛋白酶大豆琼脂上，用100 mg l〜（-1）利福平（TSA + Rif），SMAC和Fluorocult E. coli O157：H7琼脂培养基平板接种，监测存活28天。在两个温度下，与手工奶酪相比，工业中病原体的下降速度更快（P <0.05）。因此，虽然在工业样品中于4℃14天后14天后无法通过培养富集检测到O157：H7大肠杆菌，但无论接种水平如何，在28 d后1.4-1.9和4.2-5.1 log cfu g〜（-1）的种群仍然存活分别在低和高接种量的相应工匠奶酪中放置几天。与SMAC和Fluorocult相比，在TSA + Rif上的存活时间更长且更大（P <0.05），表明存在被酸损伤的细胞。有趣的是，大肠杆菌O157：H7在奶酪中14-28天后的存活率在12℃比在4℃时更好，这可能是由于酵母菌在温度滥用的奶酪表面上生长所致。工业奶酪和工匠奶酪在4℃灭活病原体的巨大差异与pH值或有机酸类型/浓度的重大差异无关，这提示了另一种抗E的作用。工业发酵剂的大肠杆菌O157：H7活性。工匠Galotyri在模拟商业储存条件下的高存活率值得关注。

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