INTERPRETATIONS OF ANTIBODY-RESPONSES TO SALMONELLA-ENTERICA SEROTYPEENTERITIDIS GM FLAGELLIN IN POULTRY FLOCKS ARE ENHANCED BY A KINETICS-BASED ENZYME-LINKED-IMMUNOSORBENT-ASSAY

Many regulatory and diagnostic programs for the detection of Salmonell a enterica serotype Enteritidis infection in commercial poultry flocks have relied on rapid Pullorum agglutination tests to screen birds bec ause of the shared antigens of S. enterica Enteritidis and S. enterica Pullorum and Gallinarum; however, the use of the enzyme-linked immuno sorbent assay (ELISA) format affords better analytical sensitivity tha n crude agglutination tests. In this study, we adapted our earlier con ventional indirect ELISA, using gm flagellin as the antigen, to a kine tics-based, computer-controlled ELISA (KELA), The KELA was used to scr een for flagellin antibody from three commercial flocks: (i) a large f lock involved in a U.S. Department of Agriculture trace back from a hu man S. enterica Enteritidis foodborne outbreak (n = 3,209), (ii) a flo ck infected with the endemic S. enterica Enteritidis serotype but whic h also had multiple other salmonella serotypes (n = 65), and (iii) an S. enterica Pullorum-infected flock (n = 12). The first flock (S. ente rica Enteritidis prevalence of 2.45% based on culture) provided a fiel d test of the KELA and allowed the calculation of diagnostic sensitivi ty (D-Sn) and diagnostic specificity (D-Sp). With a cutoff of 10 (used for screening flocks [i,e., high sensitivity]), the KELA has a D-Sn o f 95.2% and a D-Sp of 18.5%; with a cutoff of 140 (used in confirmator y hock testing [i.e., high specificity]), the KELA has a D-Sn of 28.0% and a D-Sp of 99.1%. We found that with a cutoff of 60 (D-Sn = 63.1%; D-Sp = 91.6%), we could eliminate reactions in the KELA caused by oth er non-S. enterica Enteritidis salmonellae. The KELA was also compared to two commercial rapid Pullorum tests, the Solvay (D-Sn = 94.9%; D-S p = 55.5%) and the Vineland (D-Sn = 62.0%; D-Sp = 75.3%).