In vitro activity and susceptibility to hydrolysis of S-1006

The in vitro activity of S-1006, the active component of a new orally absorbed cephalosporin, S-1108, inhibited 90% of Staphylococcus aureus isolates at less than or equal to 2 micrograms/ml, 90% of group A, B, C, F, and G streptococci and Streptococcus pneumoniae isolates at less than or equal to 0.12 microgram/ml, and all Haemophilus influenzae isolates at less than or equal to 0.06 microgram/ml. Although 50% of the members of the family Enterobacteriaceae were inhibited by less than or equal to 2 micrograms of S-1006 per ml, Enterobacter spp. and Citrobacter freundii resistant to ceftriaxone were resistant to S-1006. The MICs of S-1006 for approximately 20% of Providencia, Proteus vulgaris, and Serratia isolates were 4 micrograms/ml. S-1006 was hydrolyzed by the plasmid TEM-3, TEM-5, PSE-1, and PSE-4 beta-lactamases and by the chromosomal beta-lactamase of Enterobacter and Morganella spp. and P. vulgaris.