Selection of Aptamers against Salmonella enterica Serovar Typhimurium

Introduction: Salmonellosis is one of the most frequently reported bacterial foodborne diseases and is a major economic and public health issue worldwide, which is caused by multidrug resistant (MDR) strains such as Salmonella enterica serovar Typhimurium or S. enterica serovar Newport. There is a real need, therefore, to develop alternative molecular approaches for identifying S.Typhimurium.

Purpose: In this work, we describe the selection of aptamers against whole S. Typhimurium bacterial cells, which is different from aptamers recognize S. Typhimurium outer membrane proteins reported by Joshi et al in 2009.

Methods: A high-affinity ssDNA aptamer binding to Salmonella enterica serovar Typhimurium was obtained by a whole bacterium-based SELEX procedure. After nine rounds of selection with S. Typhimurium as the target, a highly enriched oligonucleic acid pool was sequenced and then grouped under different families on the basis of the homology of the primary sequence and the similarity of the secondary structure. Eleven sequences from different families were selected for further characterization via flow cytometry analysis.

Results:  Results showed that the sequence ST2P demonstrates affinity for S.Typhimurium much more strongly and specifically than other sequences tested. The estimated K_d values of this particularly promising aptamer was 6.33 ± 0.58 nM.

Significance: Our work demonstrates that this aptamer could potentially be used to improve the detection of S.Typhimurium.