In vitro microbiological evaluation of TEI-1194 and TEI-2012, novel antipseudomonal semisynthetic penicillins.

TEI-1194, sodium 6-[D-(-)-alpha-(coumarin-3-carboxamide)-phenylacetamide] penicillanate and TEI-2012, sodium 6[D-(-)alpha-(8-hydroxy-coumarin-3-carboxamide)-phenylacetamide] penicillanate are new semisynthetic penicillin derivatives both possessing a broad spectrum of in vitro antibacterial activities. Minimal inhibitory concentrations of both agents were compared with carbenicillin. TEI-1194 and TEI-2012 were clearly found to have more potent activities especially against Pseudomonas aeruginosa than carbenicillin. At a concentration at 6.25 micrograms/ml, 85 approximately 90% of a total of 50 strains of clinically isolated P. aeruginosa were inhibited by TEI-1194 and TEI-2012, whereas carbenicillin had no effect. Evaluation of the antibacterial activity against a series of mutants producing different levels of beta-lactamases and test of the susceptibilities to some beta-lactamases demonstrated that TEI-1194 and TEI-2012 had low susceptibility to various cephalosporinases. However, both compounds were susceptible to penicillinase from Klebsiella pneumoniae H-2 at a rate of about 15% of penicillin-G taking its absolute rate as 100.