Bio-capture of S. Typhimurium from surface water by aptamer for culture-free quantification

In this study, a DNA aptamer was used to bio-capture Salmonella enterica serovar Typhimurium from surface water collected from highly endemic zone prior to culture-free detection through Molecular-Beacon based real-time PCR assay targeting invA gene. The assay could detect S. Typhimurium cells (1 CFU/PCR or 100 CFU/ml) selectively captured by serovar specific DNA aptamer. The observations indicate that all the water samples (n=40) collected from the river Gomti were contaminated by S. Typhimurium (31400-1 × 10(7) CFU/100 ml). The pre-analytical step in the form of serovar specific DNA aptamer based bio-capture of the bacterial cell was found to enhance the sensitivity of the florescent probe based real-time PCR assay during detection of S. Typhimurium in environmental samples exhibiting natural PCR inhibitors and high background bacterial flora. The assay could be used for the regular monitoring of surface waters for forecasting and management of non-typhoidal Salmonellosis in south Asia.