Evaluation of the use of lipopolysaccharides and synthetic O-polysaccharides in i-ELISA for the serological diagnosis of brucellosis

Brucellosis remains one of the most significant diseases affecting both human and animal health in many countries worldwide, with substantial health and economic consequences.Serological tests play a key role in the diagnosis of brucellosis.This study aimed to evaluate the use of lipopolysaccharide (LPS) and synthetically derived Brucella antigens in an in-house indirect enzyme-linked immunosorbent assay (i-ELISA) for the serological diagnosis of brucellosis in milk samples collected from cattle that had experienced abortion.A total of 53 milk samples obtained from cattle herds in various provinces of Trkiye were analyzed by i-ELISA using smooth LPS (s-LPS), synthetic disaccharide/trisaccharide/tetrasaccharide, and antigens prepared from the B. abortus RB51 strain.Seropositivity rates were found to be 52.8%,39.6%, 50.9%, and 47.2% for s-LPS, disaccharide, trisaccharide, and tetrasaccharide antigens, respectively.Five serum samples reacted positively with the B. abortus RB51 antigen.Statistical analyses (McNemar and Fleiss' Kappa) revealed that s-LPS and synthetic antigens were diagnostically concordant in terms of positive/negative agreement.However, since the milk samples used in the study were not confirmed by culture or PCR, diagnostic performance parameters such as sensitivity and specificity were not calculated; classifications were made based on cutoff values determined using positive and negative control samples.As a result, although the s-LPS yielded the highest seropositivity rate, it was concluded that synthetic antigens may offer a more reliable alternative for the serological diagnosis of brucellosis due to the risk of false positives caused by crossreactions.