Syringe filter-based DNA aptamer-enzyme-linked colorimetric assay of Salmonella on lettuce

A simpler visible colorimetric and less expensive syringe enzymatic filter-based assay (SEFA) utilizing proven anti-Salmonella DNA aptamers is described which is based on a similar previously published fluorometric version of SEFA with larger filter units. The colorimetric SEFA is applied to detection of Salmonella enterica on lettuce with detection limits of less than 1000 cfu per sample. The assay is facile, rapid, inexpensive and provides sensitive presumptive detection of S. enterica serovar Typhimurium from the surface of lettuce leaves proximal to agricultural fields.