A synthetic penicillin, T-1220, is a derivative of aminobenzylpenicillin. In vitro and in vivo antibacterial activities of T-1220, ampicillin (ABPC) and carbenicillin (CBPC) were compared against gram-positive and gram-negative bacteria which were isolated from clinical specimens. The results were summarized as follows :
1) T-1220, ABPC and CBPC exhibited almost similar effectiveness against grampositive bacteria.
2) In vitro antibacterial activities against gram-negative bacteria were compared using about 100-300 clinical isolates of each species of bacteria including E. coli, K. pneumoniae, Proteus group, S. marcescence, E. cloacae and P. aeruginosa. T-1220 was found to be more effective than ABPC and CBPC, particularly against P. aeruginosa, K. pneumoniae, Proteus group and S. marcescence.
3) Antibacterial activity of T-1220 was not affected by the changes of pH and media. Addition of human serum to culture media did not show any big effect on the antibacterial activity of T-1220.
4) Greater bactericidal activity was demonstrated with T-1220; minimum bactericidal concentration (MBC) toward various strains of gram-negative rod bacteria was almost the same as their minimum inhibitory concentration (MIC) values and was less than the MBCs of ABPC and CBPC.
5) The 50 percent inhibition dose (ID50) of T-1220 was found to be much less than that of CBPC.
6) T-1220 as well as penicillin G was hydrolyzed by penicillinase (PCase). But T-1220 was very stable than CBPC against PCase derived from P. aeruginosa. Cephalosporinase (CSase) did not hydrolize T-1220, CBPC and ABPC.
7) In vivo antibacterial activities of T-1220, ABPC and CBPC were compared using the systemic infections of mice with P. aeruginosa, K. pneumoniae and E. coli. The ED50 values (mg/kg) of T-1220 were consistently less than those of ABPC and CBPC.
