Alien: Isolation might have more dangers than just the rampaging insta-kill xenomorph, but you can still complete the game without killing anyone if you so wish. Creative Assembly's Gary Napper has confirmed as much in a recent interview.
"You can get through the entire game without killing someone," Napper told GamesTM. "It's something that was, not so much a challenge, but something I felt was what the character would do. We're talking about a member of the Ripley family - they're not like characters in games that gun down civilians because they're in the way to get to the switch."
Alien: Isolation is heading to PC, PS3, PS4, Xbox 360 and Xbox One in October, and it was recently confirmed that pre-order content for the game would let us play as Ellen Ripley.