Abstract The parasite Cryptosporidium is a leading cause of life-threatening diarrhoeal disease, and effective treatment is not available. Clofazimine, an antimicrobial used for treatment of leprosy and tuberculosis, was found to have potent anti- Cryptosporidium activity but it failed in a human trial. This was attributed to poor bioavailability. Here we observed differential clofazimine susceptibility among C. parvum parasite isolates, which we exploit to identify a single genomic locus encoding the type II NADH dehydrogenase (NDH2) in an unbiased genetic cross. Targeted genetic ablation of ndh2 resulted in high-level clofazimine resistance and biochemical studies demonstrated NDH2-mediated electron transfer to clofazimine. Through genomic analyses, we uncovered heterogeneity at the ndh2 locus for C. parvum and C. hominis , and widespread carriage of a conserved attenuated allele across multiple continents. This heterogeneity allows parasites genomically linked through frequent sexual recombination to adjust to changing NDH2 requirements and predisposes Cryptosporidium to evade clofazimine treatment.
Buenconsejo et al. (2026) studied this question.