Environmentally relevant levels of sulfamethoxazole (SMX) alter the skin and gastrointestinal microbiome of adult male and female zebrafish (Danio rerio)

This study determined the effects of sulfamethoxazole (SMX) exposure on the gastrointestinal and skin microbiome of male and female adult zebrafish (Danio rerio). Adult male and female zebrafish were exposed to measured, environmentally relevant concentrations of 0, 0.75, and 304.9 µg/L SMX for 21 days. Bacterial DNA was isolated from feces and skin for 16S sequencing using NextGen Illumina MiSeq. The taxonomic data were analyzed for differences in abundance and diversity between sexes and treatment groups. There were no differences in beta diversity in the fecal and skin microbiota between males and females. However, there was a statistically significant difference between the control and low exposure concentrations of SMX for fecal samples (p < 0.05). The genera Paracoccus, Nubsella, Chryseobacterium, Delftia, and Exiguobacterium decreased in relative abundance on the skin, while an elevated abundance of Cetobacterium was detected in the low-treatment group. For the fecal samples, the low concentration of SMX increased the relative abundance of Microtrichaceae and Rhizobiaceae, and both concentrations decreased the abundance of Staphylococcaceae. Differences between males and females in the abundance of genera were detected for the fecal (e.g., Unclassified env.OPS_17), and skin microbiome (e.g., Runella, Cupriavidus, Lysobacter, Psychroglaciecola, Plesiomonas). Microbial pathways related to energy metabolism were also predicted to be altered following SMX exposure in both the fecal and skin microbiomes. This study provides essential information concerning the detrimental impact of sulfonamides on the skin and digestive system of fish and improves understanding of the possible hazards posed by antibiotic pollution to aquatic organisms.