State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China.
Zigong Center for Disease Control and Prevention, Zigong, Sichuan Province, China.
Int J Food Microbiol. 2018 Feb 2;266:295-300. doi: 10.1016/j.ijfoodmicro.2017.12.016. Epub 2017 Dec 17.
Shiga toxin-producing Escherichia coli (STEC) are globally important food-borne pathogens. The isolation of non-O157 STEC is a significant public health challenge due to the dramatic diversity of their phenotypes and genotypes. In the present study, 476 non-O157 STEC strains representing 95 different O-serogroups were used to evaluate tellurite resistance and the performance of 12 different chromogenic agars. Of 476 strains, only 108 (22.7%) strains showed the minimal inhibitory concentration (MIC) values for potassium tellurite being higher than 4μg/ml, and 96 (20.2%) strains harbored intact ter genes cluster. The presence of ter genes was significantly correlated with tellurite resistance. Six commercial chromogenic agars (TBX, MAC, SMAC, Rainbow® Agar O157, CHROMagar™ ECC, and Fluorocult O157) supported the growth of all strains. However, CT-SMAC, CHROMagar™ O157, and CHROMagar™ STEC agars exhibited 12.2%, 31.1%, and 38.0% of growth inhibition, respectively. Furthermore, 4.6%, 33.2%, and 45.0% of strains were inhibited on RBA-USDA, RBA-NT, and BCM O157 agar media. Variations in tellurite resistance and colony appearance might result in discrepant performance of non-O157 STEC recovery from different chromogenic agars. Using inclusive agars or less selective agar in combination with highly selective agar should be suggested to recover most non-O157 STEC strains, which would increase the probability of recovering STECs from complex background microflora.
产志贺毒素大肠杆菌（STEC）是全球重要的食源性致病菌。由于其表型和基因型的巨大多样性，非 O157 型 STEC 的分离是一个重大的公共卫生挑战。本研究使用了 476 株非 O157 STEC 代表 95 个不同的 O 血清群，以评估亚碲酸盐抗性和 12 种不同显色琼脂的性能。在 476 株菌株中，只有 108 株（22.7%）菌株的亚碲酸钾最小抑菌浓度（MIC）值高于 4μg/ml，96 株（20.2%）菌株携带完整的 ter 基因簇。ter 基因的存在与亚碲酸盐抗性显著相关。六种商业显色琼脂（TBX、MAC、SMAC、Rainbow®Agar O157、CHROMagar™ ECC 和 Fluorocult O157）均支持所有菌株的生长。然而，CT-SMAC、CHROMagar™ O157 和 CHROMagar™ STEC 琼脂分别表现出 12.2%、31.1%和 38.0%的生长抑制。此外，4.6%、33.2%和 45.0%的菌株在 RBA-USDA、RBA-NT 和 BCM O157 琼脂培养基上受到抑制。亚碲酸盐抗性和菌落外观的差异可能导致非 O157 STEC 从不同显色琼脂中回收的性能不一致。建议使用包容性琼脂或选择性较低的琼脂与高度选择性琼脂结合使用，以回收大多数非 O157 STEC 菌株，这将增加从复杂背景微生物群中回收 STEC 的概率。
