Chimeric protein A/G conjugate based lateral flow assay for the rapid detection of brucellosis in multiple animal species

The study highlights diagnostic efficacy of chimeric protein A/G based lateral flow assay (LFA) for on-spot diagnosis of brucellosis in various livestock species. The test device was developed using chimeric protein A/G conjugated with 40 nm colloidal gold nanoparticles as detection reagent having a strong binding affinity specifically IgG isotypes in multiple livestock species. Known positive and negative control sera samples from three livestock species and 36 Gram-negative bacterial cross-reactive hyper immune sera were used for determining the analytical sensitivity (ASn) and specificity (ASp), respectively. The diagnostic performance of LFA was evaluated in comparison with RBPT (Rose Bengal Plate Test) and indirect enzyme linked immunosorbent assay (iELISA) using 652 small ruminants, 532 bovine and 241 pig samples. The analytical sensitivity of LFA was observed up to 1:1280, 1:2560, and 1:10240 dilutions in bovine, small ruminants and pigs samples, respectively. Similarly, non-reactive to 35 Gram-negative bacterial cross-reactive hyper immune sera showed high ASp for LFA test except mild reactivity with Y. enterocolitca O9. Considering RBPT as gold standard, the diagnostic sensitivity (DSn) of protein A/G based LFA in infected farm samples was 93.9 (86.3–97.9) in small ruminants, 84.6 (54.5–98.1) in cattle and 96.5 (82.2–99.9) in swine. Considering iELISA as gold standard, the DSn of LFA was 96.3 (89.4–99.2) in small ruminants, 90 (55.5–99.7) in cattle and 96.7 (82.8–99.9) in swine. The higher performance efficacy of the LFA tests developed in this study outlines the practicality of using these rapid, easy to perform, highly sensitive and specific devices for on-spot screening of brucellosis in livestock species, which in-turn facilitate prevention, control and management of disease transmission in farms.