Agree wtih 2600, but most step-down transformers do isolate. But never assume, simply measure, or add a 1:1 iso on either side of the step down to be sure.
When powered up, just measure all 4 points of power (and all against eath ground on your outlet) and you can easily tell if it's isolated. (this is what I do to test any machine out to ensure nothing has been shorted in a normal iso before I power it up the first time)
It isolates, IF all of these measurements match:
Incomming verification:
Incomming Neutral to earth: 0 v
Incomming Hot to earth: 220 v
Incomming Hot to neutral: 220 V
Crossing verification:
Incomming Neutral to EITHER outgoing: 0 V
Incommng Hot to EITHER outgoing: 0V
Outgoing verification:
Ground to EITHER outgoing: 0V
Outgoing 1 to outgoing 2: 110V
Or just simply add a 1:1 on either side, provided it handles the voltage/amperage. It'll use a bit more power (most 1:1's meter at about 10 watts of power lost) but ensures isolation.