Assessment of the natural microbial community in a cattle manure-amended soil in presence/absence of the antibiotic sulfamethoxazole

Livestock and aquaculture activities involve the use of antibiotics. The use of manure and digestate in agricul-tural practices can introduce antibiotics and promote resistant bacteria into terrestrial and aquatic environ-ments. Sulfamethoxazole (SMX) is one of the most commonly prescribed and consumed sulfonamide antibiotic for its ability to inhibit both Gram-positive and Gram-negative bacteria. However, current knowledge about its persistence and effects on natural microbial communities are quite scarce. We investigated in microcosm laboratory experiments the effects on the structure and functioning of a soil natural microbial community treat-ed with cattle manure in presence/absence of the antibiotic SMX (20 mg/kg). At fixed times (0, 7, 13, 20, 60 days) microbiological abundance, viability, activity and SMX residual concentrations (ASE extraction and HPLC-UV detection) were analysed. Moreover, the microbial community diversity was investigated with NGS analyses. The results showed that although SMX had an initial acute negative effect on the cell abundance and viability, the antibiotic was then degraded in just a few days. The microbial community composition was influenced by the different treatments and the effect on different bacterial groups will be shown