Development of monoclonal antibodies for the rapid detection and identification of Salmonella enterica serovar Enteritidis in food sample using dot-blot assays

Abstract

Two monoclonal antibodies (mAbs) specific to Salmonella were produced from a mouse immunized with a combination of heat-killed whole-cell and formalin-fixed Salmonella enterica serovar Enteritidis (S. Enteritidis) as the antigens. The mAb SE-13D bound specifically only to S. Enteritidis, while mAb Sal-06G bound to various members of the Salmonella serogroups B, C, D, E, and I. Neither mAb demonstrated any cross-reactivity to other bacteria. The two mAbs belong to the IgM class and IgG2a subclass, respectively. Using a dot-blot assay, the detection sensitivity limits of mAbs SE-13D and Sal-06G were 107 and 106 cfu/ml, respectively. However, the detection sensitivity of both mAbs could be improved to 104 or 1 cfu/ml after pre-enriching the bacteria in tryptic soy broth (TSB) or chicken homogenate in TSB for 3 or 12 hr, respectively. Therefore, mAbs SE-13D and Sal-06G can be used as simple, rapid, specific, and effective immunological tools to directly detect and differentiate S. Enteritidis and an assortment of Salmonella serovars from other bacteria in complex crude samples such as poultry products, foods, and medical samples without the need for bacterial isolation and the conventional characterizations required by biochemical tests. Practical applications: Development of monoclonal antibody (mAb) against Salmonella is of utmost important for detection and monitoring food contamination. In this study, two mAbs: one specific to Salmonella enterica serovar Enteritidis and another one specific to several Salmonella serovars were generated. With regular pre-enriching protocol for 12 hr, the bacteria in food sample and tryptic soy broth could be detected at 1 cfu/ml with dot blot assay. Due to the rapid, specific and sensitive method for detection, both mAbs were fit for monitoring contamination of S. Enteritidis and assortment of Salmonella serovars in food samples. © 2020 Wiley Periodicals LLC