In vitro activity of HR 810, a new broad-spectrum cephalosporin.

HR 810, 3-[(2,3-cyclopenteno-1-pyridinium)methyl]-7-[2-syn-methoximino-2-(2-aminothiazole-4-yl)-acetamido] ceph-3-em-4-carboxylate, is a new semisynthetic cephalosporin derivative. The in vitro activity of HR 810 was compared with that of cefotaxime, ceftazidime, piperacillin and gentamicin using 368 strains of gram-negative and gram-positive bacteria. HR 810 was highly active against Enterobacteriaceae, being the most active of the cephalosporins against Enterobacter, Serratia and Citrobacter spp.; the MICs ranged from much less than 0.06 to 8 mg/l. The activity of HR 810 against Pseudomonas aeruginosa and Acinetobacter spp. was almost as good as that of ceftazidime. The new compound was superior to the other cephalosporins against Staphylococcus aureus and inhibited all Streptococcus faecalis strains at a concentration of 16 mg/l.