Microbially mediated abiotic transformation of the antimicrobial agent sulfamethoxazole under iron-reducing soil conditions.

Large quantities of antimicrobial agents used in livestock production are released to soils by land application of manure, but only limited information is available on mechanisms that contribute to antimicrobial fate in soils under variable biogeochemical conditions. Dissipation of the sulfonamide antimicrobial sulfamethoxazole was examined in soil microcosms incubated under different terminal electron-accepting conditions (aerobic, nitrate-reducing, Fe(III)-reducing, and sulfate-reducing). Somewhat unexpectedly, sulfamethoxazole dissipation was fastest under Fe(III)-reducing conditions, with concentrations decreasing by >95% within 1 day.