Bertolini has more tweets than Ishrak and Bush combined. Perhaps it's because he is not talking about business or healthcare 99.9% of the time. On some days he will tweet several times a day, while there will be times that we won't see a tweep out of him for days.
He tweets about music, sport, his dog Lucky and his family. And travel. Being on the road is a pervasive reality in the life of a chief executive, but Bertolini wrings humor out of it.
Bertolini also posts a ton of pictures - from scenic ones to those with people and family.
Unlike, Bush and to an extent Ishrak, Bertolini doesn't engage other people on Twitter much. It's mostly about his pictures and his content. All the more interesting given that he has more followers than either Bush or Ishrak.