The wording "negative pressure" in conjunction to cabin pressure mean that the pressure difference between inside and outside the aircraft. Normally the cabin pressure is higher than outside the A/C.
Again: It is impossible to get a negative Δ pressure on ground!
(if you donīt get this, try to understand how a door seal work)
You can get in this situation only if you descent in a very high rate for a longer time.
In this case the aircraft altitude can pass the cabin altitude.