Ultrasensitive colorimetric detection of Salmonella enterica Typhimurium on lettuce leaves by HRPzyme-Integrated polymerase chain reaction

Abstract

Salmonella enterica is one of the most encountered causative pathogens of food-borne illnesses. Outbreaks of such diseases are commonly associated with the consumption of fresh fruits and vegetables. In this study, we report a simple colorimetric strategy for the detection of S. enterica Serovar Typhimurium in fresh-cut lettuce leaves based on polymerase chain reaction (PCR) products generated by gene-specific primers integrated with the horseradish peroxidase-mimicking DNAzyme (HRPzyme). The HRPzyme sequence was integrated at the 5′ end of the forward and reverse primers specific to 16S rRNA of S. enterica Typhimurium. At the end of the PCR reaction, unamplified HRPzyme-integrated primers were folded into G-quadruplex structure in the presence of hemin and then, they catalyzed the oxidation of 2,2′-azinobis (3-ethylbenzothiazolinesulfonic acid) (ABTS) with H2O2. The intensity of oxidized ABTS colorimetric signal was linearly and inversely related to S. enterica Typhimurium concentration. The latter relationship demonstrated diagnostic potential of this rapid, simple, highly sensitive, and selective colorimetric platform for S. enterica Typhimurium detection.