Dangerous just to say "Oh, It's an Italian thread they always come loose" given that there have been many hundreds of thousands f Italian threaded bikes built since the inception of Italian threads early in the 20th century - in fact it wasn't until the Wright Brothers patented the LH threaded BB and LH pedal thread that American and then British bikes adopted a LH drive side cup thread.
If initial assembly is correctly carried out, Italian BB threads, whilst they are more prone to loosen on the drive side (due to thread precession), are generally no more problematic than are BSC.
I'd recommend getting the BB shell properly inspected by a retailer used toi dealing with material at this level to ensure that you have no thread damage (as a loose cup takes some time to make itself obvious and it may have burred the thread), having the BB shell thread chased to correct and minor damage and faced - then the BB shell should be properly degreased so that the thread locker can work correctly and have the cups correctly installed as suggested with Loctite 248 paste or similar. It is essential that the threadlocker covers the threads in this process, though - otherwise you may, over time, develop the reverse problem, of the cups seizing into the frame due to galvanic corrosion. The Loctite should prevent this.
HTH
Graeme.
