Baytril is one of the antibiotics commonly given to guinea pigs, but you can't just go and buy a bottle -- it's prescription only, as are most antibiotics. It's also not something you should be giving without veterinary supervision as it can cause guinea pigs (like all antibiotics) to go into stasis and she may need supportive care.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry