Performance of a commercial Chicken-Ovo-transferrin-ELISA on the serum of brown layer chickens infected with Gallibacterium anatis and Streptococcus zooepidemicus.

To evaluate Ovo-transferrin (OTF), a positive acute-phase protein in chickens, as a diagnostic biomarker of selected bacterial infections we checked the performance of a commercial Chicken-OTF-ELISA (ICL, Inc., Portland, OR, USA) by analytical and overlap performances using two groups of serum samples obtained from 26Gallibacterium anatis-infected and 20Streptococcus zooepidemicus-infected brown layer chickens. In addition, sera from 14 apparently healthy and 19 negative control chickens were analysed in theGallibacteriumgroup whereas sera from 20 healthy and 11 negative control chickens from theStreptococcusgroup were analysed. All calibration curves revealed high coefficients of determination (≥0.97) between optical density (OD450nm) and concentrations of OTF (mg/ml). OTF concentrations in high, medium and low pools (made of sera from a combination of infected and/or non-infected birds) were >6.4, >3.8 to <4.5 and <1.6 mg/ml in theGallibacteriumgroup, and >6.7, >3.5 to <3.7 and <1.1 mg/ml in theStreptococcusgroup, respectively. For each pool, low coefficients of intra-assay (7.8, 5.7 and 5.3) and inter-assay (15.8, 18.0 and 18.0) variations were obtained in theGallibacteriumstudy. In theStreptococcusstudy only the intra-assay variation was low (3.7, 3.8 and 6.2, respectively). The linearity check was acceptable demonstrating a straight line with slope and intercept, not deviating from one and zero, respectively, using theGallibacteriumsera, whereas theStreptococcussera deviated from the linear line. Detection limits were low (Gallibacterium, 0.01 mg/ml;Streptococcus, 0.32 mg/ml). OTF concentrations (mean ± standard error of the mean) in overlap performances were elevated in the sera of infected chickens (Gallibacterium, 4.4 ± 0.3 mg/ml;Streptococcus, 3.2 ± 0.4 mg/ml) compared with negative controls (1.7 ± 0.1 mg/ml) (P< 0.05). In conclusion, the Chicken-OTF-ELISA can be used to measure reproducible serum OTF concentrations in brown layer chickens as a response toG. anatisinfections, whereas an adjustment of dilution process is proposed to optimize to use inS. zooepidemicus-infected chickens. [ABSTRACT FROM AUTHOR]