Isolation of Cronobacter spp. isolates from infant formulas and their survival in the production process of infant formula

Abstract

Over a 24-month surveillance, three Cronobacter strains, NC041, NC830, and NC1006, were isolated from 77 powder infant formulas (3.90%). No Cronobacter was detected in liquid milk. The prevalence of Cronobacter in the prefinal product and packaged final product was 3.70% and 4.35%, respectively. The isolated Cronobacter strains were subjected to several lethal challenges including the pH, drying, disinfectant, and simulated infant formulas manufacturing process (SIFMP). The results indicated that they exhibited unusual resistance to the dry stress and disinfectant. In SIFMP, Cronobacter isolates were inoculated into three possible contamination entry points involving the stages prior to heating, drying, and filling, respectively. No Cronobacter could survive the heating. However, a high level (105 CFU/ml) of Cronobacter was detected in the samples after the inoculation at the drying point. Furthermore, the survival of Cronobacter was observed during the storage at 10°C after 7 days. The results support the hypothesis that Cronobacter contamination occurs at the stages of drying and filling, and highlight the need to improve the disinfecting measures in the manufacturing process.