One of my dachshunds has an ear infection, so he is currently on an antibiotic. It is Clavamox (amoxicillin trihydrate/clavulanate potassium), 62.5 mg. These little tablets are relatively easy to give him when I use a pill pocket made especially for this purpose (separate review). He has to take the medication twice a day, and it seems to be a pretty effective antibiotic.
My husband's cat had a jaw infection and was also put on this medication (boy, these animals can really run up the vet bills). I like the fact that the tablets are small, which helps in getting the animal to take it. My pup just started the medication, but I know from past experience that this medication has worked before. Here's hoping he doesn't have any problems with this infection that he is experiencing right now.
Clavamox seems to be a pretty effective antibiotic. It is available only by prescription.
For infections in dogs and cats, you might want to inquire of your veterinarian about Clavamox.