Probiotic L. reuteri targeting C. difficile Infection

Integration of antibiotic and probiotic therapy has the potential to lessen the public health burden to antimicrobial-associated diseases. Clostridium difficile infection (CDI) represents an important example where rational design of next generation probiotics is being actively pursued to prevent disease recurrence. Because intrinsic resistance to clinically relevant CDI antibiotics (vancomycin, metronidazole, and fidaxomicin) is a desired trait in such probiotic species, we screened several bacteria and identified Lactobacillus reuteri as a promising candidate for adjunct therapy. Human-derived L. reuteri convert glycerol to the broad-spectrum antimicrobial compound, reuterin. When supplemented with glycerol, strains carrying the pocR gene locus were potent reuterin producers with L. reuteri 17938 inhibiting C. difficile growth on a par with vancomycin. Targeted pocR mutations and complementation studies identified reuterin as the precursor-induced antimicrobial agent. Pathophysiological relevance was demonstrated when co-delivery of L. reuteri with glycerol was effective against C. difficile colonization in complex human fecal microbial communities, whereas treatment with either glycerol or L. reuteri alone was ineffective. Global unbiased microbiome and metabolomics analysis independently confirmed that glycerol precursor delivery with L. reuteri elicited changes in human microbial community composition and function that preferentially targets C. difficile outgrowth and toxicity, a finding consistent with glycerol fermentation and reuterin production. Antimicrobial resistance has thus been successfully exploited in the natural design of the human microbiome evasion of C. difficile and may provide a prototypic precursor-directed probiotic approach. Antibiotic resistance and substrate bioavailability may therefore represent critical new determinants for probiotic efficacy in clinical trials.