Typing and susceptibility of bacterial isolates from the fidaxomicin (OPT-80) phase II study for C. difficile infection

U.S.-Based National Sentinel Surveillance Study for the Epidemiology of Clostridium difficile-Associated Diarrheal Isolates and Their Susceptibility to Fidaxomicin

“…In addition, there are some data that the epidemic BI strains may have higher MICs by two dilutions than non-BI strains for vancomycin and metronidazole (4,5).…”

Comparative Susceptibilities to Fidaxomicin (OPT-80) of Isolates Collected at Baseline, Recurrence, and Failure from Patients in Two Phase III Trials of Fidaxomicin against Clostridium difficile Infection

“…The drug has a narrow spectrum of activity, with no activity against Gram-negative bacteria and many anaerobes but high activity against C. difficile (1,4,13,22). Fidaxomicin achieves a high concentration in the gut and has minimal systemic absorption.…”

In Vitro Activity of Fidaxomicin (OPT-80) Tested against Contemporary Clinical Isolates of Staphylococcus spp. and Enterococcus spp

“…Fidaxomicin, similar to other RNA polymerase inhibitors (8), is active against gram-positive organisms while exhibiting little activity against gram-negative species (7). Furthermore, fidaxomicin clinical trials (phase 2 dose-ranging and phase 3 versus vancomycin for the treatment of CDI) have demonstrated a safety profile (15) similar to that of vancomycin but with a statistically and clinically significant reduction in relapse rate (P ϭ 0.004) and improved clinical "global cure" (cure with no relapse; P ϭ 0.006) rates compared to vancomycin (2,9,12,13). While several in vitro studies have noted fidaxomicin to be highly active against gram-positive anaerobes, including C. difficile (2,6,7), data on its activity against gram-positive aerobic pathogens that can colonize the intestinal tract remain limited.…”

“…Furthermore, fidaxomicin clinical trials (phase 2 dose-ranging and phase 3 versus vancomycin for the treatment of CDI) have demonstrated a safety profile (15) similar to that of vancomycin but with a statistically and clinically significant reduction in relapse rate (P ϭ 0.004) and improved clinical "global cure" (cure with no relapse; P ϭ 0.006) rates compared to vancomycin (2,9,12,13). While several in vitro studies have noted fidaxomicin to be highly active against gram-positive anaerobes, including C. difficile (2,6,7), data on its activity against gram-positive aerobic pathogens that can colonize the intestinal tract remain limited. In this study, we evaluated the potency and activity spectrum of fidaxomicin tested against an international collection of common gram-positive isolates recovered from hospitalized patients, including VRE and MRSA.…”