Inhibitory effects of d-tryptophan on biofilm development by the foodborne Cronobacter sakazakii

This study aimed to determine the effects of d-tryptophan (d-Try) on the biofilm development of Cronobacter sakazakii. Based on preliminary test of biofilm-forming abilities of C. sakazakii isolates, the effects of d-Try on biofilm development (formation and disassembly) of a typical C. sakazakii isolate were detected by crystal violet staining, scanning electron microscopy and confocal laser scanning microscopy. Compared with biofilm formation of the corresponding control, reduction of biofilm formation by 10 mmd-Try at 24, 48, and 72 h was 87%, 84%, and 76%, respectively. In addition, a nutrient-rich medium contributes to maintenance of existing biofilm, but favours detachment when exposed to d-Try. Further analyses indicated that inhibitory effects of d-Try on biofilm development might be attributed to changes of initial adhesion between cells and the properties of the extracellular matrix. The findings presented here provided new insights for prevention and control of biofilm development of C. sakazakii.