There are two main sources for formula milk to be contaminated by Enterobacter sakazakii:one is that the milk powder  contains a small amount of Enterobacter sakazakii; the other is to enter the formula through the surrounding environment and bacteria-contaminated equipment or hands.
Most bacteria can not survive in boiling water.
 the World Health Organization recommends that no less than 70 degrees Celsius of water to prepare infant formula.