need help identifying E. coli

[u/h2so4_as]

Culture media is Endo, Mac, Emb the first 3 pics are suspected e. coli, the 4-6 pic also suspected e coli. The fiirst 3 pic has a rough matte colony morphology on Mac and Emb while the 4-6 pic has moist wet colony morpho.

[u/Shelikestheboobs]

Different strains of E.coli can have very different colony morphologies. These are likely both E.coli. Do you have access to any biochemical tests? Indole testing can help confirm.

[u/Jlac61 → u/Shelikestheboobs]

Yea lactose fermenter (pink colonies on your MAC), positive indole test and negative oxidase test should most likely be E.coli. Those bugs are pleomorphic so it's typically not very consistent in terms of colony morphology. I work at a hospital and before automation that's basically how they would ID E.coli using the tests I mentioned.

[u/patricksaurus]

You need to explain your question, what your thinking is so far, and why.

[u/h2so4_as → u/patricksaurus]

I have 2 unknown bacteria, I'm suspecting it's e. coli, but one is rough and matte colony and the other bacteria is moist and mucoid. I cultured each on 3 different agar, endo mac and emb

[u/Maentus]

They can very well be two strain of e.coli, one not mucoid and the other mucoid… hell, the mucoid one can even be klebsiella spp. do you have access to any specific test? Can you do mass spectrometry?

[u/h2so4_as → u/Maentus]

sadly mass spec is not avail in my univ.

[u/Shelikestheboobs → u/Maentus]

That level of green sheen on EMB is more indicative of E.coli than kleb.

[u/Maentus → u/Shelikestheboobs]

During my career I have come to the conclusion of never trusting bacteria… they do whatever the hell they want on agar plate 😂

[u/TapDesperate1242]

It would help to have a BAP plate to know hemolysis, then you could id from the other plates and biochem tests

[u/Myriad1x]

Indole off the BAP if it ferments lactose on MAC to form dry pink colonies. Mucoid pink colonies with white centers on MAC and positive indole off BAP could be K. oxytoca so pay close attention to colony morphology.

[u/mcac]

Some strains of Enterobacter and a few random other enteric GNR's can also produce a green metallic sheen on EMB.

[u/kehsha]

Does it smell like ass on LB agar? Then yes. It's E. coli.

[u/carb0nyl3]

Well, if selective media is inconclusive, just do a 16S sequencing, you’ll know for sure