Multicenter in vitro evaluation of SM-7338, a new carbapenem

A new carbapenem, SM-7338, was compared with imipenem, cefotaxime, and ceftazidime at five medical centers. Nearly 6,000 strains were tested by reference methods of the National Committee for Clinical Laboratory Standards, and SM-7338 inhibited the largest percentage of gram-negative bacilli. Its spectrum included all members of the family Enterobacteriaceae (99.7% were susceptible to less than or equal to 4 micrograms/ml), Pseudomonas spp. (but not Xanthomonas maltophilia), and Acinetobacter spp. The potency and spectrum of SM-7338 against the gram-positive organisms were less than those of imipenem and superior to those of ceftazidime. Only the enterococci and some oxacillin-resistant staphylococci were less susceptible to SM-7338 (MICs for 90% of isolates, greater than or equal to 8 micrograms/ml). Organisms resistant to ceftazidime were generally susceptible to SM-7338 and imipenem (76%). However, for one-third of the imipenem-resistant gram-negative bacilli (MICs, greater than 8 micrograms/ml), SM-7338 MICs were less than or equal to 4 micrograms/ml. Some endemic differences in patterns of SM-7338 activity against selected gram-negative species were found among some medical centers.