- Patients who have been treated previously with an empiric antibiotic regiment and failed treatment, both clinically and microbiologically, are eligible for the study, if they have an identified carbapenem-resistant Gram-negative pathogen which has either been shown to be nonsusceptible in vitro to each of the antibiotic(s) of the empiric antibiotic regimen or been grown from a culture performed after at least two days of the empiric antibiotic regimen