S.B.
Hi, I'm not a doctor and don't know your baby's situation, but my little girl had frequent bladder infections also. They would give her Keflex to get rid of the infection, but the only thing that stopped them was helping her keep the poop out of "there" and then giving her a cocktail of cranberry, acidophilus, EFA pills (Essential Fatty Acids oil) and vitamin C. All of those things can be put in a juice and then a bottle and they taste great. This has prevented any further infections in my daughter, once the initial infection was cleared.
My daughter was 4-1/2 - 5 when she started getting those so it is a very different age, and the cause was clear; she was not wiping properly. But boosting her immune system went a long way to prevent it from re-occuring.
Either way, if you do manage to get the medicine down in him, make sure you give him the acidophilus about an hour or two after each dose to replenish his good flora and prevent the thrush and/or candida that get out of hand when taking any antibiotic.
In a little one like this, they can't swallow the pill and if it tastes that bad, what can you do? Does the Dr. have any suggestions? Sometimes they have suppositories to administer medicines like this that are hard to take.
Best of luck to you and I'm sorry you have to go through this! It was hard enough when my daughter got them later! I can't imagine dealing with this with such a young little guy!