In-vitro activity of two new carbapenems FCE 22101 and CGP 31608 in comparison with imipenem

: The minimum inhibitory concentrations (MICs) of two new penems, CGP 31608 and FCE 22101 were evaluated against 993 aerobic Gram-positive and Gram-negative bacteria and compared with imipenem. FCE 22101 was usually two to eight-fold more active than CGP 31608 except for Pseudomonas aeruginosa against which FCE 22101 was inactive. Both new penems were less active than imipenem. MBCs were equal to 1-2 X MICs. The effects of inocula, cations and serum were minimal. The MICs and MBCs were higher at pH 8 than at pH 6 or 7. Synergy between the new penems and amikacin was detected in 30% of the strains studied. Antagonism occurred with some Gram-positive bacteria.