Contamination, persistence and dissemination of Cronobacter during the production of powdered infant formula in China in 2016

A total of 620 samples collected from two factories in China producing powdered infant formula (PIF) between July and November 2016 were analyzed for Cronobacter. Antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), and biofilm formation of Cronobacter were carried out. The results showed that 2.26% samples were positive for Cronobacter among the 33 isolates that were identified. All Cronobacter isolates were susceptible to 12 antimicrobial agents tested except one isolate which showed intermediate resistance to Chloramphenicol. PFGE analysis showed that nine clusters comprising the 33 isolates were identified, among which C8, C4, and C5 were the predominant types. All 33 isolates were capable of forming biofilm, and particularly, C. malonaticus isolates showed a good biofilm-forming ability at both 28 degrees C and 37 degrees C. The results illustrated that it is necessary for PIF manufactures to develop control measures for reducing Cronobacter contamination and its associated foodborne illness among infants.