Different factors govern surface adhesion and resilience to gastrointestinal conditions in Cronobacter sakazakii

Cronobacter species are opportunistic pathogenic bacteria present in many foods that can cause life-threatening infections in newborns and young infants. The infective potential in other vulnerable consumer groups remains unclear. In this study, twenty-eight strains of Cronobacter sakazakii from food and human clinical sources were characterized regarding their surface adhesion ability in 96-well plates at different incubation temperatures, incubation times, and cultivation media. Based on that, eight C. sakazakii isolates were selected and further studied regarding their adhesion ability to nasogastric feeding tubes and resilience to simulated gastrointestinal conditions, two key factors in the bacterium's contamination and infection strategy. Surface adhesion in nasogastric feeding tubes was assessed at 37 °C in reconstituted powdered infant formula (PIF). Gastrointestinal resilience was simulated in vitro for adult and infant digestive conditions and quantified by plate count determination and viability-based PMAxx™-qPCR. Both investigated features showed strain-dependent differences. The two factors driving surface adhesion of C. sakazakii on polystyrene were temperature (37 °C) and medium (powdered infant formula), whereas incubation time and source had no significant influence. The ability of C. sakazakii to adhere to nasogastric tubes inoculated with powdered infant formula at 37 °C highlights their biofilm-forming potential during infant feeding. C. sakazakii also demonstrated resilience to simulated infant gastrointestinal conditions. When exposed to simulated adult gastric conditions, the bacteria kept their membrane integrity, while losing their culturability, indicating a possible VBNC-like state. In the subsequent intestinal phase, bacteria regained their culturability. Our findings emphasize the need for enhanced surveillance of infections in neonates and other susceptible vulnerable individuals.