My mum has been on antibiotic after antibiotic for cellulitis in her legs and other skin infections. She's disabled and has really scaly legs due to poor circulation and the scaliness of them leads to repeated infections.
Out of the blue her doctors have called her and asked her to go for a CT scan as she can't stay on antibiotics indefinitely or have as much as she's been getting.
I can't, however, think what they might be looking for on a CT scan that could be related to antibiotics.
I did ask her to ask but as a typical 79 year old stubborn thing, she didn't.