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 less than or equal to0.015-0.5 mug/mL) including extended spectrum beta -lactamase producing strains. Less ertapenem activity was seen against Pseudomonas aeruginosa, especially ceftazidime-resistant strains (MIC50 16 mug/mL). Except for enterococci, ertapenem was active against most Gram-positive species, including beta -haemolytic streptococci (MIC90 0.03 mug/mL; 100% susceptible), viridans group streptococci (MIC90 2 mug/mL; 98.1% susceptible), and penicillin-susceptible Streptococcus pneumoniae (MIC90 less than or equal to0.015 mug/mL; 100% susceptible). Ertapenem was also very potent against Haemophilus influenzae (MIC90 0.25 mug/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.