Attachment and internalization of bioluminescent derivatives of curli and non-curli Escherichia coli O157:H7 to romaine lettuce

Escherichia coli O157:H7 is a known causative agent of foodborne illness that is frequently associated with the contamination of fresh produce. The attachment mechanisms used by E. coli O157:H7 on produce, and the interaction of bacterial cells with salad greens are not well understood. This research investigated the attachment patterns of two bioluminescent strains of E. coli O157:H7 associated with the expression of thin aggregative (curli) fimbriae. To accomplish this work, lettuce leaves were immersed in 107 – 10 8 CFU/mL liquid culture for 60 minutes. Bacteria attachment patterns of curli and non-curli E. coli O157:H7 to cut lettuce pieces and whole Romaine leaves were examined. Based on the results of these experiments, E. coli O157:H7 can attach to whole Romaine lettuce leaves and pieces, showing preferential attachment to veins and cut edges. Non-curli O157:H7 demonstrated attachment to wounds and soft rot areas of whole leaves, whereas curli producing O157:H7 bound only to fresh wounds and the central vein, if damaged. The results of this research may lead to a better understanding of potential contamination avenues of fresh produce, especially during minimal processing