Carbenicillin disodium is primarily used as an antibiotic in the treatment of infections caused by susceptible strains of bacteria, particularly Pseudomonas aeruginosa and Proteus species. It is effective in managing urinary tract infections, respiratory tract infections, and septicemia. In laboratory settings, it is often employed as a selective agent in cell culture media to prevent bacterial contamination. Additionally, it is utilized in molecular biology research for the selection and maintenance of genetically modified organisms that carry resistance markers. Its broad-spectrum activity makes it a valuable tool in both clinical and research applications.