In vitro activity and beta-lactamase stability of a new carbapenem, SM-7338.
SM-7338, a new carbapenem, inhibited most members of the family Enterobacteriaceae at MICs of 0.015 to 0.25 microgram/ml, including Klebsiella oxytoca, Citrobacter freundii, Enterobacter cloacae, and Proteus vulgaris isolates resistant to cefotaxime, ceftazidime, piperacillin, and gentamicin. It was two- to eightfold more active than imipenem, but it inhibited Pseudomonas aeruginosa at 1 to 8 micrograms/ml, which was comparable to the activity of imipenem. Haemophilus, Neisseria, and Branhamella species were inhibited by less than or equal to 0.25 microgram/ml, which was superior to the activity of imipenem. SM-7338 inhibited Staphylococcus aureus and coagulase-negative staphylococci at 0.25 microgram/ml, but for methicillin-resistant isolates MICs were 4 to 16 micrograms/ml. Group A, B, and C streptococci and Streptococcus pneumoniae were inhibited by less than or equal to 0.03 microgram/ml. Bacteroides species, including clindamycin-resistant isolates, were inhibited by 0.25 microgram/ml. There was no major inoculum size effect, and the MBCs were within a dilution of the MICs. SM-7338 was more active than imipenem at an acid pH under anaerobic conditions. Plasmid beta-lactamases of TEM-1, TEM-2, TEM-3, TEM-5, SHV-1, SHV-2, PSE-1, PSE-2, PSE-3, OXA-2, OXA-3, OXA-4, OXA-5, and OXA-7; Staphylococcus aureus enzymes; and the chromosomal beta-lactamases P-99 and K-1; Morganella species; and Proteus vulgaris did not hydrolyze SM-7338. The repeated transfer of organisms increased the MICs of SM-7338, as it did the MICs of imipenem.
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Department of Medicine, College of Physicians & Surgeons, Columbia University, New York, New York 10032.
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D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D015378:Imipenem / Q000494:pharmacology; D000077731:Meropenem; D008712:Methicillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013845:Thienamycins / Q000494:pharmacology*; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000096:biosynthesis / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D013845:Thienamycins; D065093:beta-Lactamase Inhibitors; D015378:Imipenem; D001618:beta-Lactamases; D000077731:Meropenem; D008712:Methicillin