What is causing this aggressive rash?

THIS elderly patient’s back shows large areas of erosions and peeling skin. The skin was tender but the rash was localised to his back, genitals, scrotum, groin and axillae. He’d had a similar rash four years previously, diagnosed as toxic epidermal necrolysis secondary either to amoxycillin or ceftriaxone.

Unfortunately, he had recently been started on ceftriaxone again, and this rash developed within 48 hours! It is a localised form of toxic epidermal necrolysis which is usually seen with antiepileptic drugs,