Dry transfer and adhesion of Cronobacter sakazakii on food-contact surfaces

Cronobacter sakazakii is a relevant pathogen in low-moisture foods (LMF), especially in powdered infant formulas (PIF). The objective of this study was to evaluate five matrices as dry carriers of C. sakazakii, as well as the dry transfer and adhesion capacity onto clean and conditioned stainless steel (SS) and polypropylene (PP) coupons. Soil, PIF, wheat flour, fine corn flour and whole milk powder showed potential as dry carriers, achieving counts up to 7 log CFU/g. The inoculum viability loss was greater at 37 °C, and storage time affected the inoculum in corn flour, wheat flour and soil. On clean coupons, the inoculum showed lower viability loss at 25 °C, with no significant difference among the carriers and storage times (p > 0.05). The highest counts of transferred but non-adhered cells (NAC), culturable adhered cells (CAC) and viable adhered cells (VAC) were obtained using soil as the dry carrier (p < 0.05). For pre-conditioned coupons, the highest initial NAC count was observed in PP conditioned with wheat flour. A significant difference (p < 0.05) was observed between the surfaces, except for soil conditioning. In contrast, the initial count only had significant difference (p < 0.05) between surfaces conditioned with soil. The VBNC population showed the highest counts for wheat flour on day zero. In general, soil showed a greater capacity for dry transfer and adhere C. sakazakii on abiotic surfaces, particularly on PP. Furthermore, the presence of organic residues favored pathogen adhesion and viability, indicating a higher risk of cross-contamination.