In vitro studies on the antibacterial activities of YM-13115, a new broad-spectrum cephalosporin.

The in vitro antibacterial activities of YM-13115, a new parenteral cephalosporin, were compared with those of ceftazidime, cefoperazone, and cefsulodin. The compound was highly active against the common members of the Enterobacteriaceae and 2 to 256 times more active than cefoperazone. YM-13115 was as active as ceftazidime against Citrobacter freundii, Proteus vulgaris, and Morganella morganii and two to four times more active than ceftazidime against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Serratia marcescens, Proteus mirabilis, Providencia rettgeri, and Providencia stuartii. The activity of YM-13115 against Pseudomonas aeruginosa (with MICs of 0.78 and 3.13 micrograms/ml for 50 and 90% of the isolates, respectively) was ca. 2 times that of ceftazidime, 4 times that of cefsulodin, and 16 times that of cefoperazone. Against Haemophilus influenzae YM-13115 was more active than ceftazidime. YM-13115 was less active than ceftazidime, cefoperazone, and cefsulodin against Staphylococcus aureus and Staphylococcus epidermidis. The concentrations of YM-13115 required to inhibit the growth of 90% of the isolates of Streptococcus pyogenes and Streptococcus pneumoniae were 0.78 and 1.56 microgram/ml, respectively, but concentrations above 100 micrograms/ml were required to inhibit Streptococcus faecalis. YM-13115 was not hydrolyzed by the common plasmid and chromosomal beta-lactamases. YM-13115 is extremely active against P. aeruginosa and members of the Enterobacteriaceae.