Yes, SUPERBUG is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, P 3, E 1, R 1, B 3, U 1, G 2.

Is it a valid word?

SUPERBUG is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a strain of bacteria that is resistant to all antibiotics
a strain of pest accidentally imported into Florida from the Middle East then spread to California where it is a very serious pest feeding on almost all vegetable crops and poinsettias

Also: bemisia tabaci, poinsettia strain.