Hi Glen,
How did the change of diet happen, for example was your dog on kibble then one morning changed to raw food?
Any change of diet even going from one type of kibble to another instantly without a weening period can result in an upset stomach.
Bacteria does not affect dogs as it normally affects the intestines not the stomach however dogs have a much shorter intestinal track than humans so bacteria can not grow to cause issues.
I would guess you changed diet too quickly, persistence will ease any stomach upsets your dog has however you can use some human anti-diarrhea tablets in the meantime to make sure your dog does not loose too much liquid.
Bones such as chicken bones can also be used a binding agent to solidify stools so you can feed less meat and more bone to harden up your dogs stool then introduce more meat carefully monitoring their stools.
Hope this helps
Charles
