CS-023 (R-115685), a novel carbapenem with enhanced in vitro activity against oxacillin-resistant staphylococci and Pseudomonas aeruginosa

Objective: To compare the in vitro activities of the carbapenem, CS-023, four representative beta-lactam antibiotics and levofloxacin, against 970 Gram-positive or Gram-negative US clinical isolates. Methods: Susceptibilities of bacteria chosen for their varying levels of resistance to the comparator agents were determined by NCCLS microdilution methodology. Results: CS-023 exhibited activity comparable to that of imipenem against most Gram-positive isolates, but was similar to8-fold more potent against oxacillin-resistant staphylococci. It was comparable to meropenem against most Gram-negative isolates, but was 4- to 8-fold more potent against five isolates of meropenem-resistant Pseudomonas aeruginosa. Conclusions: If tissue and body fluid concentrations >8 mg/L can safely be achieved, further studies of CS-023 are warranted to determine its clinical efficacy.