Enzyme-linked immunosorbent assay with a Salmonella enteritidis antigen for differentiating infected from vaccinated poultry

The specificity and sensitivity of indirect ELISA, based on the use of four different antigenic extracts obtained from a clinical isolate of Salmonell a enteritidis, were compared with those obtained with the gm-flagellin base d ELISA (IDEXX). A total of 116 serum samples from salmonellae free, natura lly infected and vaccinated hens were studied. The results showed that the indirect ELISA, based on lipopolysaccharide (LPS), O-polysaccharide (PS) or membrane sediment (SD) antigens, enable the identification of a greater nu mber of infected birds and discriminated field antibody responses from vacc inal ones better than the commercial IDEXX test. The indirect ELISA that us ed a O-polysaccharide rich fraction (PS) proved to be the most specific and sensitive test, suggesting that this indirect ELISA could be used to confi rm IDEXX results, especially when the differentiation between vaccinated an d infected poultry is required.