Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Switzerland Winterthurerstrasse 272, CH-8057 Zurich, Switzerland.
J Food Prot. 2010 Jan;73(1):88-91. doi: 10.4315/0362-028x-73.1.88.
Food is an important vehicle for transmission of Shiga toxin-producing Escherichia coli (STEC). To assess the potential public health impact of STEC in Swiss raw milk cheese produced from cow's, goat's, and ewe's milk, 1,422 samples from semihard or hard cheese and 80 samples from soft cheese were examined for STEC, and isolated strains were further characterized. By PCR, STEC was detected after enrichment in 5.7% of the 1,502 raw milk cheese samples collected at the producer level. STEC-positive samples comprised 76 semihard, 8 soft, and 1 hard cheese. By colony hybridization, 29 STEC strains were isolated from 24 semihard and 5 soft cheeses. Thirteen of the 24 strains typeable with O antisera belonged to the serogroups O2, O22, and O91. More than half (58.6%) of the 29 strains belonged to O:H serotypes previously isolated from humans, and STEC O22:H8, O91:H10, O91:H21, and O174:H21 have also been identified as agents of hemolytic uremic syndrome. Typing of Shiga toxin genes showed that stx(1) was only found in 2 strains, whereas 27 strains carried genes encoding for the Stx(2) group, mainly stx(2) and stx(2vh-a/b). Production of Stx(2) and Stx(2vh-a/b) subtypes might be an indicator for a severe outcome in patients. Nine strains harbored hlyA (enterohemorrhagic E. coli hemolysin), whereas none tested positive for eae (intimin). Consequently, semihard and hard raw milk cheese may be a potential source of STEC, and a notable proportion of the isolated non-O157 STEC strains belonged to serotypes or harbored Shiga toxin gene variants associated with human infections.
食品是产志贺毒素大肠杆菌（STEC）传播的重要载体。为了评估瑞士生牛乳奶酪中 STEC 对公众健康的潜在影响，这些奶酪是由牛奶、山羊奶和绵羊奶制成的半硬质或硬质奶酪，共检测了 1422 个样本，软质奶酪检测了 80 个样本，对 STEC 进行了检测，并对分离株进行了进一步的特征分析。通过 PCR，在生产者层面采集的 1502 个生牛乳奶酪样本中，有 5.7%的样本在富集后检测到 STEC。STEC 阳性样本包括 76 个半硬质奶酪、8 个软质奶酪和 1 个硬质奶酪。通过菌落杂交，从 24 个半硬质奶酪和 5 个软质奶酪中分离出 29 株 STEC 菌株。24 株可分型菌株中，有 13 株属于 O 抗血清型 O2、O22 和 O91。29 株分离株中，超过一半（58.6%）属于之前从人类中分离出的 O:H 血清型，并且还发现了 O22:H8、O91:H10、O91:H21 和 O174:H21 型 STEC 是溶血性尿毒综合征的病原体。志贺毒素基因分型显示，只有 2 株携带 stx(1)，而 27 株携带编码 Stx(2)组的基因，主要是 stx(2)和 stx(2vh-a/b)。stx(2)和 stx(2vh-a/b)亚型的产生可能是患者严重后果的一个指标。9 株菌携带 hlyA（肠出血性大肠杆菌溶血素），而没有一株菌携带 eae（紧密素）。因此，半硬质和硬质生牛乳奶酪可能是 STEC 的潜在来源，分离的非 O157 STEC 菌株中相当一部分属于与人类感染相关的血清型或携带志贺毒素基因变异体。
