Sick Duck- Could it be salmonellosis?

[Aviculturist]

I have a three month old duck (female) that started having extremely bad balance about 2 and a half weeks ago. In the beginning she could walk but when she tried to keep up with the other ducks she lost her balance and would skid onto her chest. I took her to the vet and they believe the issue is Enterococcus and prescribed Tetracycline. My duck, Opal, has been on Tetracycline for 11 days with no improvement. If anything she has gotten worse. She can no longer stand for long without flipping over backwards onto her back. She is able to right herself and gets back up but flips over again and again. She also has diarrhea and her eyes are 'watering'. I have recently switched her to Sulfamethazine because she seemed to be losing her vision and her head was swelling while taking the Tetracycline. It is possible that the diarrhea developed as a result of taking the antibiotics as well, because she did not have diarrhea until starting Tetra. I currently give her a small pinch of Sulfa-vitamin powder mixed in about 500ml of water, with electrolytes and for probiotics I mix in the poop from one of my healthy ducks (as recommended by the vet). She is still eating and drinking on her own. I have her in a small cat kennel to keep her from flipping about and injuring herself. She has a bed of clean straw (which I change often due to the diarrhea). I bathe her in a sink every couple of days but she flips about in the water as well (no balance).
Has anyone dealt with symptoms like these? If so, did you find a medication that helped or did it just need to run its course? My duck has been on antibiotics for quite some time with no improvement. I hate to see her suffering.
Please see attached video

 

[mesafox101]

pictures would help

 

[Aviculturist]

Video has been added

 

[Aviculturist]

Opal's eyes watering

 

[onaharley]

Oh my! Have you talked to your vet about this? What do they think?

 

[CayugaJana]

@Miss Lydia @casportpony @WVduckchick @ViolinPlayer123
Any of you have experience? This looks just awful!

 

[CayugaJana]

If it's some sort of bacteria causing the symptoms, wouldn't it be from one that produces a neurotoxin? Like botulism? Aflatoxin from grain?
Anyways, hopefully one of the people tagged above have experience.....

 

[casportpony]

Opal's eyes wateringView attachment 1167067

Why does the vet think it's Enterococcus?

 

[MagpieDucks]

Sorry I can't be much more help. Just try to keep her comfy and warm. Hopefully you'll see some improvement.

 

[Aviculturist]

Why does the vet think it's Enterococcus?

The vet seemed to think her behaviour is caused by a bacterial infection...but then I wonder why the antibiotics seem to be ineffective. Correct me if I'm wrong, but from what I understand enterococcus is many different forms of bacterial infection. The antibiotics should have worked by now, should they not?
I also have Opal on niacin, to no avail.

Any other suggestions?