If you're caught without antibiotics, and you need them, there's little that will do much good. In a bad situation, drug stores might already be
looted, or guarded, and you be unable to find some.
There is an animal medication that has an extra long shelf life, and can be found at vet clinics and a lot of hardware/animal supply places. It's
called "terramycin". It is a powder that is water soluble, and the dosage is determined by body weight.
Don't be put off by the fact that it's for animals, we're talking emergencies here. It's a wide spectrum antibiotic that is almost a clone to
penicillin. It is recommended for beef, poultry,swine sheep and bees. It contains oxytetracycline, so check ahead of time to be sure you are not
allergic.
I"M NOT A DOCTOR, and this is not medical advice, but your dog may get sick.