Yoshida T, Sato M, Hirai K
Division of Food Hygiene, Nagano Research Institute for Health and Pollution, Japan.
J Vet Med Sci. 1998 Mar;60(3):311-4. doi: 10.1292/jvms.60.311.
Raw milk samples from bulk tanks of a total of 943 farms, which corresponded to approximately 60% of all dairy farms in Nagano Prefecture were examined for Listeria species between December 1990 and April 1991. Listeria spp. were isolated from 29 (3.1%) of 943 milk specimens. In the southern, central, eastern and northern areas of the prefecture, Listeria spp. were isolated from 6.1% (22/362), 1.5% (4/272), 1.4% (2/143) and 0.6% (1/166) of samples, respectively. Listeria monocytogenes was isolated from three (0.3%) bulk tanks in the southern area: two of the strains isolated from two different farm bulk tanks were serovar 4b, and the other one was 1/2a. Besides, between February 1991 and January 1992, 504 samples of raw milk from farm bulk tanks were collected nine times from 56 farms in the southern area, where the prevalence of Listeria spp. was the highest, and examined for the seasonal variation in the presence of Listeria spp. The prevalence of Listeria spp. was higher in spring (14.3%) than in autumn (4.8%). The 56 farms were divided into three groups according to the prevalence of Listeria spp., namely, three farms in Group 1 gave a high contamination rate (50% < or =), 14 farms in Group 2 a low contamination rate and the remaining 39 farms in Group 3 no recovering of Listeria spp. Sixteen strains of L. monocytogenes serovar 4b were isolated from four farms.
1990年12月至1991年4月期间，对长野县约60%的奶牛场（共943个农场）的储奶罐中的生牛奶样本进行了李斯特菌属检测。从943份牛奶样本中分离出李斯特菌属的有29份（3.1%）。在该县的南部、中部、东部和北部地区，分别从6.1%（22/362）、1.5%（4/272）、1.4%（2/143）和0.6%（1/166）的样本中分离出李斯特菌属。在南部地区，从三个储奶罐（0.3%）中分离出了单核细胞增生李斯特菌：从两个不同农场储奶罐中分离出的两株菌株为血清型4b，另一株为1/2a。此外，在1991年2月至1992年1月期间，从南部地区（李斯特菌属患病率最高）的56个农场的储奶罐中九次采集了504份生牛奶样本，检测李斯特菌属存在情况的季节性变化。李斯特菌属的患病率在春季（14.3%）高于秋季（4.8%）。根据李斯特菌属的患病率，将这56个农场分为三组，即第1组有三个农场污染率高（50%及以上），第2组有14个农场污染率低，其余39个农场在第3组未检出李斯特菌属。从四个农场分离出了16株单核细胞增生李斯特菌血清型4b。
