To develop a shuttle vector that can be used for transforming STI-causing serovars of C. trachomatis, we modified the pGFP::SW2 plasmid by first using a blasticidin S deaminase gene (BSD) from the vector pLenti6.3 [17] to replace the chloramphenicol acetyltransferase gene (CAT) as a fusion partner of GFP (Figure 1). The gene discussed is CAT; the disease is sexually transmitted disease.