Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Finland.
Int J Food Microbiol. 2012 Apr 2;155(1-2):69-72. doi: 10.1016/j.ijfoodmicro.2012.01.021. Epub 2012 Feb 1.
Yersinia enterocolitica is a psychrotrophic, facultative anaerobic zoonotic bacterium belonging to family Enterobacteriaceae and it can be transmitted from pigs to humans through pork. The growth of bacteria belonging to Enterobacteriaceae and aerobic spoilage bacteria is usually effectively restricted by 20% or more CO(2) enriched atmosphere at refrigerated temperatures. In this study, 40 samples of meat strips from pig cheek (musculus masseter) and 40 samples from hind leg (m. semimembranosus) muscles were packaged in modified atmosphere (MA) (30% CO(2)/70% O(2)) and stored at 6°C for 12d. Twenty naturally contaminated samples per muscle type were studied on days 1 and 13. Violet red bile glucose (VRBG) and de Man Rogosa Sharpe (MRS) agar plates were used for enumeration of Enterobacteriaceae including Y. enterocolitica and lactic acid bacteria, respectively. During the 12-d storage at 6°C in MA, the mean number of bacteria on pork strips of cheek meat was increasing from 1.6 to 4.5 log cfu/g and from 3.1 to 7.2 log cfu/g on VRBG and MRS agar plates, respectively. Most of the oxidase-negative isolates on VRBG plates, which were isolated from the cheek meat samples after 12-d cold storage in MA, were identified as Y. enterocolitica 4/O:3. The mean number of this pathogen was 4.1 log cfu/g varying between 2.3 and 5.4 log cfu/g. The pH of the cheek meat and leg meat was measured on days 1 and 13, and it remained high (pH>6) in most cheek meat samples during the storage. No Y. enterocolitica 4/O:3 was isolated from meat strips of hind leg. This study shows that cheek meat of slaughter pigs is contaminated with Y. enterocolitica 4/O:3 and that this pathogen can grow well on raw pork packaged in MA at 6°C even in the presence of high number of lactic acid bacteria.
肠炎耶尔森氏菌是一种嗜冷、兼性厌氧的人畜共患病细菌，属于肠杆菌科，可通过猪肉从猪传播到人。在冷藏温度下，富含 20%或更多二氧化碳的气氛通常可以有效限制肠杆菌科细菌和需氧腐败菌的生长。在这项研究中，40 份来自猪颊（咀嚼肌）的肉条和 40 份来自后腿（半膜肌）的肌肉样本被包装在改良气氛（MA）（30% CO 2/70% O 2）中，并在 6°C 下储存 12 天。每块肌肉类型各有 20 个自然污染样本在第 1 天和第 13 天进行研究。紫红红胆葡萄糖（VRBG）和 de Man Rogosa Sharpe（MRS）琼脂平板分别用于计数肠杆菌科，包括肠炎耶尔森氏菌和乳酸菌。在 MA 中 6°C 下储存 12 天期间，颊肉猪肉条上的细菌数量从 1.6 增加到 4.5 log cfu/g，在 VRBG 和 MRS 琼脂平板上分别从 3.1 增加到 7.2 log cfu/g。在 MA 中冷藏 12 天后，从颊肉样本中分离出的 VRBG 平板上大多数氧化酶阴性分离株被鉴定为肠炎耶尔森氏菌 4/O:3。该病原体的平均数量为 4.1 log cfu/g，范围为 2.3 至 5.4 log cfu/g。在第 1 天和第 13 天测量了颊肉和腿肉的 pH 值，在储存过程中，大多数颊肉样本的 pH 值仍然很高（pH>6）。在后腿肉条中未分离出肠炎耶尔森氏菌 4/O:3。本研究表明，屠宰猪的颊肉受到肠炎耶尔森氏菌 4/O:3 的污染，即使在存在大量乳酸菌的情况下，这种病原体也可以在 6°C 下用 MA 包装的生猪肉中很好地生长。
