Distinct anthelmintic classes do not affect gut bacteria, and bacteria do not alter nematocidal efficacy in Caenorhabditis elegans.

Soil-transmitted helminth infections are widespread and can impair children's nutrition and development. Anthelmintics may interact with the intestinal microbiota; however, they should not disrupt microbes, and microbial metabolism should not reduce drug efficacy. Using Caenorhabditis elegans and representative Gram-positive and Gram-negative gut bacterial lineages, Escherichia coli and Lactobacillus reuteri , respectively, we tested interactions with fluopyram, ivermectin, and levamisole. None of the drugs affected either bacterial growth, and neither bacterial lineage altered nematocidal efficacy. These results help elucidate bacteria-anthelmintic-nematode interactions using tractable experimental models; their direct relevance to in vivo intestinal infections remains to be confirmed.