Six isolates of E.coli on Endo agar with biochemical slope. All of them are fermenting lactose and mannitol and don'ferment cellobiose (seemingly positive results around cellobiose discs on first three plates are due to strong acidification of Endo agar from mannitol and sucrose diffusing in the medium). Two isolates don't ferment sucrose. All of them produce acid and gas from glucose.

General description of testing on Endo agar with biochemical slope is here.

Isolate No.2 is an enteropathogenic E. coli (EPEC) O55.

Compare these lactose positive isolates with lactose delayed E.coli strains.

Cultivation 24 hours, 37°C in an aerobic atmosphere.