Immunosensors combined with a light microscopic imaging system for rapid detection of Salmonella

The objective of this study was to demonstrate the applicability of immunosensors combined with a light microscopic imaging system (LMIS) for the rapid detection of Salmonella in chicken. The reactivity and specificity of purified anti-Salmonella polyclonal antibodies (pAbs) were compared with commercial pAbs using indirect ELISA. After the optimum antibody concentration was determined, the immobilization of antibody was confirmed using an atomic force microscopy (AFM). The immunosensor combined with LMIS method was applied to chicken for Salmonella detection. No significant difference in reactivity was found between the purified and commercial anti-Salmonella pAbs over the entire concentration range (p > 0.05). In addition, the purified anti-Salmonella pAbs showed sufficient specificity for 11 non-Salmonella bacterial strains and reactivity for 10 chicken-associated Salmonella serovars. The optimal antibody concentration for immobilization on the sensor was determined to be 100 μg/mL. The AFM images confirmed the binding of antibody on a sensor by providing irregular and globular surface features. When applied to chicken, the number of detected Salmonella increased quantitatively as the concentration of inoculated Salmonella increased. The limit of detection was 103 cfu/chicken, which was considerably lower than those of other biosensor methods. With the advantage of direct observation and enumeration of Salmonella on the sensors, the immunosensor combined with LMIS method detected Salmonella in chicken in a specific, sensitive, simple, and practical manner.