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

Abstract

A piezoelectric quartz crystal (PQC) based screening test for Salmonella enteritidis infection in chickens and eggs is described. AT-cut quartz crystals of 10 MHz were used as reaction carrier, on which recombinantly expressed S. enteritidis proteins were immobilized to capture the associate antibodies from chicken serum or egg-white samples. Once the surface had been modified with antigen protein, only one sample incubation of 15-min duration was required to provide frequency changes corresponding to the binding of the target antibodies. Serum and egg-white samples from infected chickens produced significant binding with signal ranging from 200 to 900 Hz depending on 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. enteritidis and to provide ‘yes’ or ‘no’ (e.g. positive or negative) results. The clinical sensitivity and specificity of the PQC sensors were 100% and 92.9%, respectively. Comparison of sample testing results obtained from PQC sensors and licensed enzyme-linked immunoassay (ELISA) demonstrated that the PQC sensors could also be used to estimate the antibody titers. To perform dipping coating quartz crystal with precious protein, a micro container has been developed.