Thermal Inactivation ofEnterobacter sakazakii in Rehydrated Infant Formula

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Abstract
The presence of low levels ofEnterobacter sakazakii in dried infant formula have been linked to outbreaks of meningitis, septicemia, and necrotizing enterocolitis in neonates, particularly those who are premature or immunocompromised. In the current study, the ability of 12 strains ofE. sakazakii to survive heating in rehydrated infant formula was determined at 58°C with a submerged coil apparatus. The observed D58-values ranged from 30.5 to 591.9 s, with the strains appearing to fall into two distinct heat resistance phenotypes. The z-value of the most heat-resistant strain was 5.6°C. When dried infant formula containing this strain was rehydrated with water preequilibrated to various temperatures, a more than 4-log reduction inE. sakazakii levels was achieved by preparing the formula with water at 70°C or greater.