Bacterium (2006)

When a handful of friends stumble upon the abandoned building, they come face to face with a biological weapons experiment gone catastrophically wrong. They also confront a maniacal scientist who predicts life on Earth will end in 48 hours if the accelerated bacterial mutation cannot be halted.

As the virulent, flesh-hungry contagion spreads from person to person, rendering each host into a pile of infectious ooze, it begins to multiply and increase in size. A covert military force sent in to contain the spread and destroy the organism discovers the extent of the slithering mutation, but by then it's far too late for conventional tactics. Extreme measures are required if anyone is left standing in one solid piece to do battle.