Maturation and Survival of Cronobacter Biofilms on Silicone, Polycarbonate, and Stainless Steel after UV Light and Ethanol Immersion Treatments

Abstract

Cronobacter sakazakii cells in biofilms formed on silicone, polycarbonate, and stainless steel coupons immersed in reconstituted powdered infant milk formula were treated with ethanol (10 to 70%) and UV light (12 to 2,160 mW·s/cm2) as antibacterial treatments. Biofilm maturation curves were determined after immersion at 25°C for up to 144 h. Populations increased after subsequent immersion at 25°C for 24 h in reconstituted powdered infant milk formula to the respective maximum levels of 7.96, 7.91, and 6.99 log CFU per coupon. Populations attached to silicone and polycarbonate surfaces to a greater extent than to stainless steel (P < 0.05). Treatment with 10% ethanol did not cause a significant decrease in the level of C. sakazakii, but treatment with 30, 40, and 50% ethanol reduced the levels to approximately 1.73, 3.02, and 4.17 log CFU per coupon, respectively. C. sakazakii was not detected on any coupon after treatment with 70% ethanol or 2,160 mW·s/cm2 UV light. A synergistic effect of sequential ethanol and UV treatments was not observed.