"The pathogen was designed to affect all non-botanical life forms.
All the animals, the 'meat', if you will... either kill them outright
or use them as incubators to spawn a hybrid form, highly aggressive."
After;
"The original liquid atomized to particles when exposed to the air."
Aka, the intended method of deployment.
The Engineers weren't chestbursted, they exploded as the decapitated Engineer exploded.
Owing to the holes in their, arms, legs, chest and head.
The eventual fate of Fifield and Holloway, which both started becoming aggressive and losing their senses.
But Holloway received a minute dosage, and Fifield received a massive dosage.
No mutation.
The worms birthed the Alien worms,
as the Humans birthed the Neomorphs.
Yeah, the sacrificial Engineer utilized a different liquid entirely.