Selective detection of Salmonella typhimurium in the presence of high concentrations of masking bacteria

This article presents the results of an investigation into the ability of a magnetoelastic biosensor to detect Salmonella typhimurium, with high specificity, even in the presence of high concentrations of masking bacteria. Magnetoelastic biosensors are mass sensitive devices comprised of a magnetoelastic material that serves as the transducer and bacteriophage as the bio-recognition element. The sensors were tested individually with several different genus bacteria (Salmonella typhimurium, Salmonella entertidis, Escherichia coli O157:H7 and Listeria monocytogenes) to compare the bioprobe’s affinity towards species other than the target analyte. The effect of the presence of one masking bacteria (E. coli) and two masking bacteria (E. coli and L. monocytogenes) in a mixture with S. typhimurium upon the response of the biosensor was studied. It was observed that the response of the sensors followed similar trends; however the sensitivity and the frequency changes were slightly lower for the mixtures. The sensitivity of the sensors exposed to only S. typhimurium was 161 Hz decade⁻¹ and in mixtures with one and two masking bacteria were 131 Hz decade⁻¹ and 127 Hz decade⁻¹, respectively. Binding kinetics studies show that the dissociation constant (K _d) and the binding valency (1/n _H) samples with only S. typhimurium are 149 cfu mL⁻¹ and 2.49, respectively.