Type III secretion system (TTSS) clusters contain virulent genes of both animal and plant Gram-negative bacteria. The full length (933 bp) gene of bipD, a member of TTSS cluster of Burkholderia pseudomallei, was isolated by PCR amplification from B. pseudomallei DNA and cloned into pGEX 4T-1. GST-BipD fusion protein and BipD protein obtained by removal of GST using thrombin were employed to detect the presence of B. pseudomallei antibodies in sera obtained from melioidosis and non-melioidosis patients by immunoblotting. Sensitivity and specificity of BipD protein was 100% and 91.1%, respectively, whereas that of fusion protein was 77.8% and 90.0%, respectively.