Application of pneumococcal choline binding protein A in the diagnosis of community-acquired pneumonia

Abstract:

Objective: To investigate the applicative value of enzyme-linked immunosorbent assay (ELISA) reaction model which took pneumococcal choline binding protein A (rCbpA) as antigen in detecting patients with community acquired pneumonia (CAP). Methods: The specific primers of cbpA gene sequence were designed and synthetized, and proliferated according to PCR, finally, the cloning plasmids PGM-T/cbpA and expressing plasmids were constructed. Recombinant rCbpA was expressed after the inducing of isopropyl phosphorothioate (IPTG); ELISA model (rCbpA as antigen) was constructed and was used to detect IgM and IgG in the control group and CPA group. And results were compared with sputum culture and blood culture and were analyzed by Chi-square text. Results: The recombinant protein CbpA was obtained and rCbpA-ELISA was established. The sensitivity detected by the rCbpA-IgM in pneumococcal CAP patients was 22.5%, which had no statistically significant difference by blood and sputum culture method (χ²=3.529, P=0.060; χ²=0.075, P=0.785). But its specificity was 100%, which was significantly higher than that by sputum culture (χ²=12.754, P=0.000). The sensitivity detected by rCbpA-IgG mode to detect pneumococcal CAP patients was 50%, which was statistically different from the sensitivity by blood culture and sputum culture (χ²=17.635, P=0.000; χ²=7.912, P=0.005). Conclusion: The serum recombinant protein rCbpA has high specificity to IgM and high sensitivity to IgG. Moreover, advantages including fast detection and objective judgment result, can improve the diagnostic value of pneumococcal infections.