I have no knowledge of Ben's condition and treatment. Critical care can mean a wide range of things and possibly needing a transplant again COULD be a worst case scenario. There is possibly a good chance once they find the right antibiotic he could recover, but right now he's "critical" and if things do not improve he could die or need a transplant. This is based off personal experience and watching friends deal with life threatening problems. Medical speak can be like law speak, nebulous.
He is a fighter and an athlete. I hope he makes it through this serious situation and lives a healthy life and can enjoy his family for a long, long time