观察后，沿培养管的管壁加入数滴靛基质试液，液面呈玫瑰红色，为靛基质阳性；呈试剂本色，为靛基质阴性。本底对照应为MUG阴性和靛基质阴性。如MUG阳性，靛基质阳性，判供试品检出大肠埃希菌；如MUG阴性，靛基质阴性，判供试品未检出大肠埃希菌；如MUG阳性，靛基质阴性，或MUG阴性，靛基质阳性，则应取胆盐乳糖培养基的培养物划线接种于曙红亚甲蓝琼脂培养基的平板上，培养18~24小时。
After observation，add several drops of iodole test solution along the wall of cultivation tube, the indole is positive if the liquid level is rose bengal; the indole is negative if the test solution presents its natural color. The background contrast should be MUG negative and indole negative. If MUG positive and indole positive present, the E. coli is detected out of samples; if MUG negative and indole negative present, there is no E. coli tested out of samples; if MUG positive and indole negative present, or MUG negative and indole positive present, take cultivation material of bile salt lactose cultivation medium streak and inoculate it onto plate of Eosin methylene blue agar, and cultivate it for 18~24 hours..