In vitro evaluation of ertapenem (MK-0826), a long-acting carbapenem, tested against selected resistant strains.

Ertapenem (MK-0826) is a novel, long-acting parenteral carbapenem. The purpose of this in vitro study was to test ertapenem's activity against a collection of multiply-resistant strains of gram-positive and -negative bacteria isolated from locations worldwide, and to examine its bactericidal activity and ability to act in a synergistic manner in combination with other antimicrobial agents. Ertapenem was active against a variety of gram-negative pathogens, with particular potency noted for Escherichia coli and Klebsiella pneumoniae (MIC90s < or =0.015-0.5 microg/mL) including extended spectrum beta-lactamase producing strains. Less ertapenem activity was seen against Pseudomonas aeruginosa, especially ceftazidime-resistant strains (MIC50 16 microg/mL). Except for enterococci, ertapenem was active against most gram-positive species, including beta-haemolytic streptococci (MIC90 0.03 microg/mL; 100% susceptible), viridans group streptococci (MIC90 2 microg/mL; 98.1% susceptible), and penicillin-susceptible Streptococcus pneumoniae (MIC90 < or =0.015 microg/mL; 100% susceptible). Ertapenem was also very potent against Haemophilus influenzae (MIC90 0.25 microg/mL; 100% susceptible). Bactericidal action was observed versus staphylococci, E. coli, and K. pneumoniae, and at least an additive effect was detected against the majority of the strains tested when ertapenem was combined with ciprofloxacin or gentamicin. These results from testing 902 organisms indicate that ertapenem appears to be a promising broad-spectrum carbapenem with a possible role against some emerging resistant species.