Effect of Competing Foodborne Pathogens on the Selectivity and Binding Kinetics of a Lytic Phage for Methicillin-Resistant Staphylococcus aureus Detection

Abstract

The selectivity and binding kinetics of a lytic phage as a new bio-recognition element were compared and evaluated. The selectivity was studied by exposing the magnetoelastic (ME) biosensor to individual cultures of Escherichia coli O157:H7 (EO), Listeria monocytogenes (LM), Salmonella Typhimurium (ST), Vibrio parahaemolyticus, Yersinia enterocolitica, and methicillin-resistant Staphylococcus aureus (MRSA). A dose response of the ME biosensor obtained from serially increasing concentrations of MRSA was then compared with those obtained from MRSA in a mixture of other competing bacteria. The number of MRSA bound on the measurement sensor was 12,206 ± 750 cells/sensor, which was significantly greater than the number of other competing bacteria bound on the sensor (P < 0.001). The dose responses of sensors to increasing concentration of MRSA and MRSA in a mixture of other competing bacteria were similar, indicating that the resonant frequency shifts of the ME sensor were dependent on the concentration of MRSA. The binding valency and dissociation constant (cfu/mL) of the lytic phage with MRSA, MRSA + LM, MRSA + LM + EO, and MRSA + LM + EO + ST were calculated as 3.3 ± 0.2 and 62.5 ± 11.0, 3.7 ± 0.2 and 56.2 ± 11.8, 3.4 ± 0.2 and 59.4 ± 10.5, and 3.7 ± 0.2 and 56.0 ± 10.7, respectively. This study demonstrated that lytic phages were able to bind with MRSA specifically and selectively even in the presence of other competing bacteria.