Sick dog.

Did they take a stool sample?  You must be very worried.  I hope the antibiotics do the trick and your dog feels better soon.  Please keep us posted.

Is she spayed? 
 
How long has she been on antibiotics? 
 
Sometimes antibiotics take time to be effective, but I would SURELY keep the vet in the loop and let them know today, if possible, there's no change. 
 
Salmonella poisoning is pretty tough ... was there a particular reason the vet thot that??  raw meat? raw eggs? pig ears? 
 
When you say the gums are pink -- did you mean 'pale' or normally pink?
 
 

yes, he's neutered.
i'm not sure, just pink, i havent actually seen them myself.

did they take stool sample or blook work?

Callie .. CAN you read??  "he" normally means MALE woman!!! 
 
Shoot ... that's what happens when I post on my way out the door.  I'm not usually so brain dead. 
 
I take it this isn't your dog??  It sounds like there is some serious inflammation in the intestinal tract or even a partial obstruction.  Is the dog defacating AT ALL?  Other than passing blood and mucous?  The belly will get tight if there is pain ... and if there is a sore obstruction the body will try to 'pass' it with mucous (and the blood could be coming from the site of some obstruction that is causing bleeding.
 
I'd ask for a pack cell volume (which will tell if there is internal bleeding) and either x-rays, or probably even better would be an ultrasound (which can be pricey but often can be a life-saver).
 
This is why the question "is the dog pooping" is so important:
 
If there is an obstruction, then poop can't get 'out' (at least partially blocking or fully blocking the intestinal tract).  That means that anything the dog ate AFTER the obstruction happened just backs up the intestinal tract all the way to the stomach.  The bit that spills over into the stomach forces stomach acid to continue to pour into the stomach to 'digest' that ... but whatever is in the stomach can't get OUT of the stomach (follow me?)
 
The dog may have thrown up where they couldn't see and at this point because the dog feels so nauseus it can't/won't put more food IN the stomach and the foam can simply be bile and stomach acid that comes back up to relieve the pressure in the stomach. 
 
This is where vets often get stumped -- because the obstruction can, at this point, look like infection (particularly if there is some foreign object causing the system to go septic) ... but if the dog can't keep down antibiotics then it's tough. 
 
If the obstruction is something that will show on an x-ray great ... but often it's not.  That's where an ultrasound can give a better picture of what's going on.  And often it's the only thing that will save the life.  
 
I had a friend who had a small poodle become obstructed.. This dog was NOT a 'chewer' .... that just wasn't his persona at all.  X rays showed nothing.  He just got sicker and sicker ... ultimately they did an ultrasound which showed a fibrous mass and at least gave the vets a place TO do surgery.
 
For some unknown reason Cedar had chewed on an old hammock that was stored.  (had someone spilled food on it?? maybe) but he had a wad of cotton fiber in his intestinal tract.  But they went thru every diagnosis from salmonella, to liver to pancreatitis and beyond ... til FINALLY they found where the obstruction was.  He lived ... and lived for many years after. 
 
Hopefully these folks have a good vet who will think out of the box.   And you're a good friend to try to find help for them.