Shimamura Yuko, Shinke Momoka, Hiraishi Miki, Tsuchiya Yusuke, Egawa Mizuki, Ohashi Norio, Masuda Shuichi
School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
(ORCID: https://orcid.org/0000-0003-0801-483X [Y.S.]).
J Food Prot. 2020 Jun 1;83(6):928-934. doi: 10.4315/0362-028X.JFP-19-278.
The influence of muscle fiber direction (parallel or perpendicular) in relation to the inoculation surface on migration of Salmonella Enteritidis, Staphylococcus aureus, and Escherichia coli into raw chicken breasts was examined. Chicken breast samples with two types of surface fibers (running parallel or perpendicular to the surface) were inoculated with cultures of each bacterium. Inoculated samples were stored for 5 min, 1 h, or 24 h at 4°C. After storage, the samples were divided into segments, and bacterial counts were determined in different regions (inoculation surface, inoculation surface to 1 cm, 1 to 2 cm, 2 to 4 cm, and 4 to 6 cm). The migration of bacteria did not change at 5 min or 1 h regardless of fiber direction. However, after 24 h each bacterium was detected at 4 to 6 cm in the pieces of sample with a perpendicular muscle fiber surface cut. Although these bacteria were detected at 4 to 6 cm in samples with muscle fibers perpendicular to the inoculated surface, these results do not clearly indicate that bacteria migrated into the chicken breast. To monitor actual migration of bacteria into the chicken breast, the tops of the perpendicular muscle fibers of the breast sample were inoculated with bioluminescent E. coli Xen-14. Various regions of the breast sample (inoculation surface and cut surfaces at 1, 2, 4, and 6 cm) were stamped directly on growth medium. Culture revealed that the bacteria migrated directly under the contaminated site and dispersed along the surface of the chicken breast segments. More bacteria distributed laterally than migrated directly below the contamination site. These results suggest that the direction of the muscle fibers is a major factor influencing migration of pathogenic bacteria into chicken breast.
研究了肌肉纤维方向（平行或垂直）与接种面的关系对肠炎沙门氏菌、金黄色葡萄球菌和大肠杆菌向生鸡胸肉内迁移的影响。用两种表面纤维类型（与表面平行或垂直）的鸡胸肉样本接种每种细菌培养物。接种后的样本在4℃下储存5分钟、1小时或24小时。储存后，将样本分成段，并在不同区域（接种面、接种面至1厘米处、1至2厘米处、2至4厘米处和4至6厘米处）测定细菌数量。无论纤维方向如何，在5分钟或1小时时细菌迁移情况未发生变化。然而，24小时后，在垂直肌肉纤维表面切割的样本块中，在4至6厘米处检测到了每种细菌。尽管在肌肉纤维垂直于接种面的样本中在4至6厘米处检测到了这些细菌，但这些结果并未明确表明细菌迁移到了鸡胸肉内部。为了监测细菌向鸡胸肉内的实际迁移情况，用生物发光大肠杆菌Xen-14接种鸡胸肉样本垂直肌肉纤维的顶部。将鸡胸肉样本的各个区域（接种面以及1厘米、2厘米、4厘米和6厘米处的切割面）直接印在生长培养基上。培养结果显示，细菌直接迁移到污染部位下方，并沿鸡胸肉切块表面扩散。横向分布的细菌比直接迁移到污染部位下方的细菌更多。这些结果表明，肌肉纤维方向是影响病原菌向鸡胸肉内迁移的主要因素。
