I also thought of natural antibiotics like honey or garlic as substitutions, but I also thought that they would only help with gut infections (e.g. no use for infected hip joint after transplant) - is that not so?
Speaking more generally, there is limited interest from big pharma in the use of natural or herbal products because they will have to spend a ton of money on clinical trials to prove effectiveness, but they won't get the patent protection necessary to recoup the cost of R&D, like they would with synthetic drugs.