大肠埃希菌O157:H7分离鉴定过程中赫尔曼埃希菌的鉴别

目的：鉴别大肠埃希菌O157：H7和赫尔曼埃希菌。方法：观察菌株在山梨醇麦康凯，营养琼脂及Chromagar O157培养基上菌落形态。生化试验检测菌株的生化特性，血清凝集试验检测菌株的O157和H7抗原，聚合酶链反应法检测O157和H7特异性基因。结果：在营养琼脂培养基上，5株赫尔曼埃希菌均产黄色色素，2株O157：H7菌不产色素；在Chromagar O157培养基上，2株O157：H7菌株呈紫红色，2株赫尔曼埃希菌株呈蓝色，其余3株赫尔曼埃希菌株呈黄绿色。O157：H7菌株KCN试验均为阴性，而赫尔曼埃希菌阳性。O157和H7抗血清坡片凝集试验，7析均为强凝集。O157：H7菌株与O157单克隆抗血清玻片凝集试验均为强凝集，而赫尔曼埃希菌均不凝集。O157：H7菌株O157和H7特异性基因均为阳性，赫尔曼埃希菌均为阴性。结论：赫尔曼埃希菌与O157多克隆抗血清有交叉反应，但单克隆抗血清能区分O157：H7和赫尔曼埃希菌。KCN试验和特异性基因检测亦能鉴别这两种菌。在营养琼脂和Chromagar O157培养基上的菌落形成也有助于两菌的区分。

Identification of Escherichia Hermanii during separating Escherichia Coli O157 :H7

Objective: To distinguish Escherichia hermanii (E. hermanii) from Escherichia coli (E. coli) O157:H7. Methods: Bacterial colonies were observed on Sorbitol-MacConkey agar, Nutrient agar and Chromagar O157. Biochemical characteristics were tested with biochemical assay. Serologic agglutination assay was used to detect O and H antigens of the tested strains. Polymerase chain reaction was used to identify specific genes of O157 and H7. Results: The five strains of E. hermanii presented yellow on nutrient agar, while the two strains of E. coli O157:H7 became milky-white. The two strains of E. coli O157:H7 appeared purple on Chromagar O157. Two of the five strains of E. hermanii (01E038 and 01E057) appeared blue, and the others (01E039, 01E045 and 01E059) appeared yellow-green on Chromagar O157. The strains of E. coli O157:H7 were negative while the strains of E. hermanii were positive for the test of KCN. Both O157 anti-serum and H7 anti-serum strongly agglutinated the tested strains in slide agglutination assay. The strains of E. coli O157:H7 were strongly agglutinated with O157 single colony anti-serum, while the strains of E. hermanii were not in slide agglutination assay. Specific genes of O157 and H7 were positive for the tested strains of E. coli O157:H7, while those were negative for the trains of E. hermanii. Conclusions: The Crossing-reaction presents between E. hermanii and O157 anti-serum. O157 single colony anti-serum, the test of KCN and specific genes of O157 and H7 are used to differentiate E.coli O157 and E. hermanii. Characteristics of bacterial colonies on nutrient agar and Charomagar O157 also help differentiate them.