In vitro activity of Ro 09-1428 compared to other cephalosporins

The in vitro activity of Ro 09-1428, a new catechol-type parenteral cephalosporin, was compared to that of ceftazidime, E-1040, cefpirome and cefepime against gram-positive and gram-negative organisms. Ro 09-1428 inhibited group A streptococci at less than or equal to 0.12 micrograms/ml, and group B, C and G streptococci and Streptococcus pneumoniae at 0.5 micrograms/ml, whereas for Staphylococcus aureus Ro 09-1428 had MICs of 8-16 micrograms/ml similar to ceftazidime and E-1040. Against Pseudomonas aeruginosa Ro 09-1428 was the most active agent, inhibiting isolates at less than or equal to 0.12-2 micrograms/ml, and inhibited ceftazidime-resistant isolates. The majority of Escherichia coli, Klebsiella spp., Proteus mirabilis, Citrobacter diversus, Providencia, Salmonella and Shigella were inhibited by less than or equal to 0.5 micrograms/ml as with the other cephalosporins. For most Citrobacter freundii and Enterobacter cloacae Ro 09-1428 had higher MICs of 4-16 micrograms/ml; most ceftazidime-resistant isolates of these species were resistant. Anaerobes, enterococci and Listeria monocytogenes were resistant to Ro 09-1428. Ro 09-1428 was not hydrolyzed by TEM-1, TEM-2, Staphylococcus aureus PC-1, Moraxella catarrhalis Bro-1, Enterobacter P-99, Pseudomonas aeruginosa Sabath-Abraham or Klebsiella beta-lactamases, but was hydrolyzed by TEM-3, TEM-7 and TEM-9. Ro 09-1428 was markedly less active at an acid pH.