On a new penicillin derivative, T-1220, some experimental and clinical trials were performed and the following results were obtained.
1) The sensitivity of gram negative bacilli of clinical isolates was clearly superior to that of carbenicillin or ticarcillin. There were marked differences between MICs measured with inoculum sizes of original ov1ernight broth culture and its 100-fold dilution.
2) In the rats with liver impairment by CCl4, biliary and urinary excretions of T-1220 were less than that of normal controls.
3) Two patients with pneumonia were treated with T-1220 and the effect was evaluated as good in both cases. No side effect was observed.