Clostridium difficile infection (CDI) is a common, debilitating
infection with high morbidity and mortality. C. difficile causes
diarrhea and intestinal
inflammation by releasing two toxins, toxin A and toxin B. The
macrolide antibiotic fidaxomicin was recently shown to be effective in treating CDI, and its beneficial effect was associated with fewer
recurrent infections in CDI patients. Since other
macrolides possess anti-inflammatory properties, we examined the possibility that
fidaxomicin alters C. difficile toxin A-induced ileal
inflammation in mice. The ileal loops of anesthetized mice were injected with
fidaxomicin (5, 10, or 20 μM), and after 30 min, the loops were injected with purified C. difficile toxin A or
phosphate-buffered saline alone. Four hours after toxin A administration, ileal tissues were processed for histological evaluation (epithelial cell damage, neutrophil infiltration, congestion, and
edema) and
cytokine measurements. C. difficile toxin A caused histologic damage, evidenced by increased mean histologic score and ileal interleukin-1β (IL-1β)
protein and
mRNA expression. Treatment with
fidaxomicin (20 μM) or its primary metabolite,
OP-1118 (120 μM), significantly inhibited toxin A-mediated histologic damage and reduced the mean histology score and ileal IL-1β
protein and
mRNA expression. Both
fidaxomicin and
OP-1118 reduced toxin A-induced cell rounding in human colonic CCD-18Co fibroblasts. Treatment of ileal loops with
vancomycin (20 μM) and
metronidazole (20 μM) did not alter toxin A-induced histologic damage and IL-1β
protein expression. In addition to its well known antibacterial effects against C. difficile,
fidaxomicin may possess anti-inflammatory activity directed against the intestinal effects of C. difficile toxins.