Survival of Enterobacter sakazakii in a dehydrated powdered infant formula

A quantity of dehydrated powdered infant formula was prepared to contain Enterobacter sakazakii strain 607 at approximately 106 CFU/ml when rehydrated according to the manufacturer's instructions. The survival of the microorganism in the dry formula was followed for 2 years, during which samples periodically were rehydrated and analyzed for viable E. sakazakii. During the initial 5 months of storage at room temperature, viable counts declined approximately 2.4 log cycles. During the subsequent 19 months, the concentration of viable E. sakazakii declined an additional 1.0 log cycle. These results indicate that a small percentage of E. sakazakii cells can survive for extended periods in dehydrated powdered infant formula.