I saw this all the time when I worked in commercial HVAC back in the 80’s. Cooling tower water was routinely never treated properly.
The water used to get so thick full of algae you could slice it with a knife. It was like pudding.
Customers would never spend the money to have the water treated with a regular PM program.
This was a disaster waiting to happen.
GSK appears to have an environmental monitoring program, and presumably a good maintenance program. I wonder how the bacteria got in their cooling tower.