7-(Alpha-(1-methyl-4-pyridinothio)-acetamido) cephalosporanic acid.

7-[alpha-(1-Methyl-4-pyridiniothio)-acetamido] cephalosporanic acid, referred to herein as BL-S 217, is a new broad-spectrum semisynthetic cephalosporin that offers several advantages over cephalothin. A comparison of the activity in vitro of these antibiotics indicates that BL-S 217 is about eightfold more effective against Streptococcus pyogenes and Diplococcus pneumoniae. Against gram-negative bacteria, BL-S 217 possesses a broader antibacterial spectrum than cephalothin, particularly against members of the Enterobacteriaceae family; e.g., BL-S 217 inhibited over 20% more strains of both Escherichia coli and Klebsiella than cephalothin and also showed some advantage in tests against Salmonella and Enterobacter. Overall, of 208 strains of Enterobacteriaceae tested, 172 were susceptible to BL-S 217 compared to 149 for cephalothin. BL-S 217 was less bound to human serum proteins than cephalothin and gave higher peak blood levels in mice after intramuscular administration. The LD(50) of BL-S 217 in mice after subcutaneous administration was in excess of 4,000 mg/kg. When administered by the same route to mice experimentally infected with cephalothin-sensitive bacterial strains, this new cephalosporin was 20 times more effective than cephalothin in S. pyogenes and D. pneumoniae infections and 3 to 4 times more efficacious in an E. coli infection. Its therapeutic efficacy was comparable to that of cephalothin in infections produced by strains of Staphylococcus aureus, Klebsiella pneumoniae, and Proteus mirabilis.