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Gut Bacteria Interactions Can Impact Efficacy of Antibiotics Against C. Difficile, Study Finds

Interspecies interactions between gut bacteria may alter the efficacy of antibiotics against Clostridioides difficile, according to a study appearing this week in PLOS Biology. This finding, the researchers note, may help guide treatment strategies. C. difficile can infect the human intestines, and it is known that gut microbiota can inhibit the bacterium's growth and ability to persist through a phenomenon known as colonization resistance. How the microbiota affects C. difficile antibiotic susceptibility, however, is not clear. To investigate, University of Wisconsin-Madison researchers used a bottom-up assembly of human gut communities to examine the contribution of interspecies interactions on the response of C. difficile to two antibiotics commonly used against the pathogen: vancomycin and metronidazole. They find that gut microbes rarely increase the pathogen's ability to grow at high antibiotic concentrations, but frequently enable it to grow at low antibiotic concentrations. In microbial communities with antibiotic-sensitive species that also compete with C. difficile, the pathogen's growth is enhanced in the presence of low concentrations of antibiotics due to competitive release, the study's authors write. The researchers also uncover a specific bacterial species that increases C. difficile's tolerance to metronidazole. The findings, they state, "highlight the need to consider biotic interactions in the design of future therapeutic treatments to eradicate pathogens.