confers_resistance_to_drug_class antibiotic resistant gene variant or mutant confers_resistance_to_drug_class antibiotic resistant nfsA antibiotic_resistance The nfsA-encoded nitroreductase is the major oxygen-insensitive nitroreductase present in E. coli. NfsA uses only NADPH and has broad electron acceptor specificity. Mutations in nfsA cause resistance to nitrofurazone and furazolidone. Resistance to nitrofurantoin via mutation of nfsA reduces the fitness of clinical isolates of E. coli. ARO:3003754 nitrofuran antibiotic