Chou Chung-Hsi, Silva Juan L, Wang Chinling
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State 39762-9825, USA.
J Food Prot. 2006 Apr;69(4):815-9. doi: 10.4315/0362-028x-69.4.815.
Raw channel catfish fillets collected from three processing plants during four time periods were tested for the presence of Listeria species. Listeria monocytogenes was the predominant Listeria species found in these catfish fillets, with 25 to 47% prevalence. Other Listeria species, such as L. welshimeri, L. innocua, L. ivanovii, L. grayi, and L. seeligeri, were also found. L. monocytogenes isolates were further fingerprinted by a repetitive element PCR. Forty distinctive electrophoretic types (ETs) and three genetic clusters were determined by Dice coefficient analysis and UPGMA (unweighted pair group method using arithmetic averages). Twenty of 40 ETs were represented by a single isolate, and the other 20 ETs were represented by 2 to 11 isolates. Thirty-five ETs, represented by 76 isolates, were found in processing plant A, B, or C and designated plant-specific types. The remaining five ETs, represented by 21 isolates, were found in multiple plants and designated nonplant-specific types. In addition, 10 ETs from 52 isolates were found repeatedly during different seasons. Plant-specific and nonplant-specific L. monocytogenes coexisted in processed catfish fillets. Some isolates were persistently found in processed fillets, suggesting that either the current sanitation procedures used by these plants are inadequate or that these isolates originated from the natural habitats of the catfish. The results also suggest that the repetitive element PCR is a useful tool for differentiating L. monocytogenes subtypes and can be used for tracing the source of a contamination.
在四个时间段从三个加工厂采集的生的斑点叉尾鮰鱼片被检测是否存在李斯特菌属。在这些鮰鱼片里发现的主要李斯特菌属是单核细胞增生李斯特菌，患病率为25%至47%。还发现了其他李斯特菌属，如威氏李斯特菌、无害李斯特菌、伊氏李斯特菌、格氏李斯特菌和斯氏李斯特菌。单核细胞增生李斯特菌分离株通过重复元件PCR进一步进行指纹分析。通过Dice系数分析和UPGMA（非加权组平均法）确定了40种独特的电泳类型（ETs）和三个基因簇。40种ETs中有20种由单个分离株代表，其他20种ETs由2至11个分离株代表。在加工厂A、B或C中发现了由76个分离株代表的35种ETs，并指定为工厂特异性类型。其余由21个分离株代表的5种ETs在多个工厂中发现，并指定为非工厂特异性类型。此外，在不同季节反复发现了来自52个分离株的10种ETs。工厂特异性和非工厂特异性的单核细胞增生李斯特菌在加工后的鮰鱼片中共存。在加工后的鱼片里持续发现了一些分离株，这表明这些工厂目前使用的卫生程序要么不足，要么这些分离株源自鮰鱼的自然栖息地。结果还表明，重复元件PCR是区分单核细胞增生李斯特菌亚型的有用工具，可用于追踪污染源。
