[Microbiology] issues with suspected E. coli

[Nathan Tisdell]

I am currently taking an introduction to microbiology class and am having
issues with a strain of bacteria.  We have run SIM tests, Citrate, MR-VP,
TSI and EMB tests.  Every test points to it being E. Coli except for the EMB
plate, instead of turning purple with a green sheen, it stayed colorless.  I
did not streak for isolation, just a straight streak across the medium.  If
someone could let me know about something that I might be missing, I would
greatly appreciate it.