Survival and growth of Cronobacter species (Enterobacter sakazakii) in wheat-based infant follow-on formulas

Abstract

Aims: To determine the survival and growth characteristics of Cronobacter species (Enterobacter sakazakii) in infant wheat-based formulas reconstituted with water, milk, grape juice or apple juice during storage. Methods and Results: Infant wheat-based formulas were reconstituted with water, ultra high temperature milk, pasteurized grape or apple juices. The reconstituted formulas were inoculated with Cronobacter sakazakii and Cronobacter muytjensii and stored at 4, 25 or 37°C for up to 24 h. At 25 and 37°C, Cronobacter grew more (>5 log10) in formulas reconstituted with water or milk than those prepared with grape or apple juices (c. 2-3 log10). The organism persisted, but did not grow in any formulas stored at 4°C. Formulas reconstituted with water and milk decreased from pH 6·0 to 4·8-5·0 after 24 h, whereas the pH of the formulas reconstituted with fruit juices remained at their initial pH values, c. pH 4·8-5·0. Conclusions: Cronobacter sakazakii and C. muytjensii can grow in reconstituted wheat-based formulas. If not immediately consumed, these formulas should be stored at refrigeration temperatures to reduce the risk of infant infection. Significance and Impact of the Study: The results of this study will be of use to regulatory agencies and infant formula producers to recommend storage conditions that reduce the growth of Cronobacter in infant wheat-based formulas. © 2008 The Society for Applied Microbiology.