Pardon me,

Some people live in areas where water is in the range of 20-45 (naturally) before it goes in the heater. Me included. Actually in the summer some folks install water coolers to their main water tanks !!

Despite the temp, we have not heard of this bacteria.
So, do you think that other factors maybe involved, like water salinity ..etc. (maybe IN ADDITION to the temp) ?

p.s.
I live in the Middle East, and our feed water is on the salty side : around 2000-4000 TDS