Genotyping of Cronobacter (Enterobacter sakazakii) strains isolated from an infant formula processing plant.

Cronobacter spp. are occasional contaminants of infant food processing establishments and have been implicated in rare cases of neonatal infections. The control of these organisms during the processing of infant formula and identification of possible contaminating sources is of importance to manufacturers. In this study, infant formula processing sites were monitored for the presence of Cronobacter spp. (E. sakazakii) in 2007. Cronobacter were isolated using ISO/TS 22964 and simultaneously using a newly developed differential method, Cronobacter Screening Broth (CSB). Clonal types of Cronobacter strains in the environment, raw materials, and products were investigated using PFGE and RAPD in order to shed light on the possible dissemination routes within the facility. Over the course of the study, a total of 153 Cronobacter isolates were obtained from 46 end-products, 23 raw materials and 44 environmental samples. The 153 Cronobacter isolates represented 71 PFGE pulso-types, with 24 pulso-types containing multiple isolates. Clonal isolates present in products could be matched to indistinguishable pulso-types in raw materials and in the environment, however no strains were identified that were present in both the environment and raw materials. Although the majority of the isolates were obtained from products, the largest diversity of isolates was observed in raw materials. This may indicate raw materials as a significant source of Cronobacter entry into the production facility with subsequent selection for strains that are able to persist within the factory environment.