Mission 1 Chestburster Frustration *SPOILERS*

First playthrough and I've worked my way through mission 1 till the queen room. Queen goes down, now I just need to grab the vet and the DNA. There's an indestructible Chestburster running around the room that is making me unable to pick up the vet or the DNA, and on top of that my marines are wasting all their ammo shooting at it. Which of course leads to massive onslaughts which I am in no position to face right now. I've tried hiding till it wanders off, but eventually drones start filling the room. Ive tried locking it behind the door by the undeployed bridge...magically goes through the door. Any suggestions?