Potential negative effect of long-term exposure to nitrofurans on bacteria isolated from wastewater

Nitrofurans are broad-spectrum bactericidal agents used in a large quantity for veterinary and human therapy. This study reports the long-term impact of two nitrofuran representatives, nitrofurantoin (NFT) and furaltadone (FTD) on the bacterial strains Sphingobacterium siyangense FTD2, Achromobacter pulmonis NFZ2, and Stenotrophomonas maltophilia FZD2, isolated from a full-scale wastewater treatment plant. Bacterial whole genome sequencing was used for preliminary strains characterization. The metabolomic, electrochemical, and culture methods were applied to understand changes in the bacterial strains after 12-month exposure to nitrofurans. The most significantly altered metabolic pathways were observed in amino acid and sugar metabolism, and aminoacyl-tRNA biosynthesis. Disrupted protein biosynthesis was measured in all strains treated with antibiotics. Prolonged exposure to NFT and FTD also triggered mutagenic effects, affected metabolic activity, and facilitated oxidative stress within the cells. Nitrofuran-induced oxidative stress was evidenced from an elevated activity of catalase and glutathione S-transferases. NFT and FTD elicited similar but not identical responses in all analyzed strains. The results obtained in this study provide new insights into the potential risks of the prolonged presence of antimicrobial compounds in the environment and contribute to a better understanding of the possible impacts of nitrofuran antibiotics on the bacterial cells.