Administration of probiotic kefir to mice with Clostridium difficile infection exacerbates disease

• Lifeway Kefir probiotic supplementation exacerbates Clostridium difficile disease in mice.
• Probiotic-induced disease is unrelated to C. difficile burden or toxin production.
• Profound host-differences in probiotic efficacy highlight the need for additional clinical trials.

Lifeway® kefir, a fermented milk product containing 12 probiotic organisms, is reported to show promise as an alternative to fecal microbiota transplantation for recurrent Clostridium difficile infection (CDI). We employed a murine CDI model to study the probiotic protective mechanisms and unexpectedly determined that kefir drastically increased disease severity. Our results emphasize the need for further independent clinical testing of kefir as alternative therapy in recurrent CDI.