Piezoelectric quartz crystal based veterinary diagnosis for Salmonella enteritidis infection in chicken and egg

A piezoelectric quartz crystal (PQC) based screening test for Salmonella en teritidis infection in chickens and eggs is described. AT-cut quartz crysta ls of 10 MHz were used as reaction carrier, on which recombinantly expresse d S. enteritidis proteins were immobilized to capture the associate antibod ies from chicken serum or egg white samples. Once the surface had been modi fied with antigen protein. only one sample incubation of 15-min duration wa s required to provide frequency changes corresponding to the binding of the target antibodies. Serum and egg-white samples from infected chickens prod uced significant binding with signal ranging from 200 to 900 Hz depending o n the different antibody titer, whereas samples from non-infected chickens produced no or minimal frequency changes. A cut-off threshold, 180 Hz, was set up for the PQC sensor. With reference to this value, PQC sensors could screen chickens and eggs suspected to have been infected with S. enteritidi s and to provide 'yes' or 'no' (e.g. positive or negative) results. The cli nical sensitivity and specificity of the PQC sensors were 100% and 92.9%, r espectively. Comparison of sample testing results obtained from PQC sensors and licensed enzyme-linked immunoassay (ELISA) demonstrated that the PQC s ensors could also be used to estimate the antibody titers. To perform dippi ng coating quartz crystal with precious protein, a micro container has been developed. (C) 2001 Elsevier Science B.V. All rights reserved.