Prevalence of Cronobacter spp. in a powdered infant formula processing environment

From November 2005 to August 2006, microbiological analyses were performed in a processing plant for powdered infant formula (PIF) to estimate the occurrence and dissemination of Cronobacter spp. and the contamination levels of Enterobacteriaceae in the processing environment. In total 867 samples were collected from the dry processing environment including powders from vacuum cleaners and filtering (sieving) machines, fluids from the drains and swabs from contact surfaces. In total 35 samples in 14 out of 35 tested locations were positive for Cronobacter spp. Positive samples were found in environmental powders (94.3%) and two fluids (5.7%). The Cronobacter spp. prevalence was highest in powders from vacuum cleaners with 28.0% positive samples on a single location. While powders from the sensitive agglomeration section or production (sieving) had contamination rates of 10.7% or below 3.4%, respectively. In addition vacuum powder samples from the filling and can filling line were positive with 5.3 and 8.0%, respectively. High levels (> 500 cfu/g) of Enterobacteriaceae were found in seven locations out of 21 tested powder locations. This fact emphasizes the importance of monitoring of the processing environment to implement effective measures to improve the safety and hygiene in PIF, a very sensitive product.