Rifalazil treats and prevents relapse of clostridium difficile-associated diarrhea in hamsters

Abstract

Although vancomycin and metronidazole effectively treat Clostridium difficile-associated diarrhea and colitis (CDAD), their use is associated with a high incidence of relapsing C. difficile infection. Rifalazil is a new benzoxazinorifamycin that possesses activity against Mycobacterium tuberculosis and gram-positive bacteria. Here we compared rifalazil and vancomycin for effectiveness in preventing or treating clindamycin-induced cecitis in a hamster model of CDAD. Golden Syrian hamsters were injected subcutaneously with clindamycin phosphate (10 mg/kg), followed 24 h later by C. difficile gavage. Hamsters received by gavage for 5 days vehicle, vancomycin (50 mg/kg), or rifalazil (20 mg/kg) either simultaneously with (prophylactic protocol) or 24 h after C. difficile administration (treatment protocol). While all vehicle-administered animals became moribund within 48 h of C. difficile administration, no rifalazil- or vancomycin-treated animals in either protocol showed signs of morbidity after 7 days. Ceca of rifalazil-treated animals showed absence of epithelial cell damage, significantly reduced congestion and edema, and less, but not statistically significantly less, neutrophil infiltration compared to those of vehicle-treated animals. In contrast, vancomycin-treated animals demonstrated severe epithelial cell damage and mildly reduced congestion and edema. Moreover, hamsters relapsed and tested C. difficile toxin positive (by enzyme-linked immunosorbent assay) 10 to 15 days after discontinuation of vancomycin treatment. None of the rifalazil-treated hamsters showed signs of disease or presence of toxins in their feces 30 days after discontinuation of treatment. Our results indicate that once daily rifalazil may be superior to vancomycin for curative treatment of CDAD.

FIG. 1.

Protective effect of rifalazil in C. difficile-associated histopathology in hamster cecum. A histologic evaluation of hematoxylin-and-eosin-stained cecal sections of hamsters exposed to C. difficile and various antibiotic treatments is shown.

FIG. 2.

Kaplan-Meier survival analysis of hamsters infected with C. difficile and treated at day 0 (prophylactic treatment) with vancomycin or rifalazil. All C. difficile-treated hamsters became moribund within 2 days after the challenge. All vancomycin-treated animals became moribund between days +14 and +24, while all rifalazil-treated animals survived for the duration of the observation period (P < 0.05, rifalazil versus vancomycin treatment, n = 4 per group).

FIG. 3.

Kaplan-Meier survival analysis of hamsters receiving treatment 24 h after a C. difficile challenge. All vehicle-treated animals became moribund within 2 days of the challenge. Only 35% of the vancomycin-treated animals survived after day +24 of the observation period, whereas 100% of the rifalazil-treated animals survived for up to 32 days of follow-up (P < 0.001, n = 10 to 14 per group).

FIG. 4.

Kaplan-Meier survival analysis of animals infected with C. difficile and receiving rifalazil treatment for 1 to 5 days. Four animals were treated for 1, 2, 3, 4, or 5 days. The analysis indicates that 5 days of rifalazil treatment is required for 100% survival of CDAD (P < 0.01 compared to other groups).