Survival of Enterobacter sakazakii in infant cereal as affected by composition, water activity, and temperature

Abstract

Enterobacter sakazakii infections in preterm neonates and infants have been epidemiologically associated with consumption of reconstituted powdered infant formula. The bacterium has been isolated from grain, infant cereals, and cereal factory environments. A study was done to determine the survival characteristics of E. sakazakii initially at populations of 0.31 and 5.03 log CFU/g of infant rice cereal ( a w 0.30, 0.45–0.46, and 0.68–0.69). Cereal was stored at 4, 21, and 30 °C and populations were monitored for up to 12 months. Survival of the pathogen in infant rice, barley, oatmeal, and mixed grain cereals ( a w 0.63–0.66, 0.76, or 0.82–0.83) initially containing a population of 4.93–5.64 log CFU/g and held at 4, 21, and 30 °C up to 24 weeks was determined. Populations decreased significantly ( p⩽0.05) in all cereals stored at 21 and 30 °C regardless of a w. Increases in a w or storage temperature accelerated the rate of death of E. sakazakii in dry infant cereals. However, at an initial population of 0.31 log CFU/g, E. sakazakii survived in rice cereal ( a w 0.30–0.69) for up to 12 months at all storage temperatures. Survival of E. sakazakii was not affected by the composition of dry infant rice, barley, mixed grain, and oatmeal cereals (initial a w 0.63–0.83) stored for up to 24 weeks at 4, 21, or 30 °C. This study demonstrated that E. sakazakii can survive for up to 12 months in infant cereals having a wide range of a w when storage is at temperatures simulating those to which they may be exposed during distribution, at retail, and in the home.