I work with a reptile rescue group. I have looked after a few RI cases now. We ended up keeping one of the rehab cases. She is about the sweetest snake I have ever 'met' anyway. She was being treated when she arrived (batryl) no culture. She got better but not cured. After the cycle was over she was still ok not 100% we watched and waited 6 months later ( cultures are not very effective during or immediately after antibiotics have been administered) We took her for a culture (lung wash) the vet proscribed a different cycle on antibiotics and over a year and a half later she is 100% better.
The advise that I got from my vet was culture culture culture! The advise I read here is the same and the advise I give is also the same. Yes recovery is quite possible especially if the case is not advanced and the correct drugs and dose is delivered.