Effects of Antibiotics on Enzyme Activity and Intestinal Microorganisms of Opsariichthys bidens

In this study, the effects of antibiotics on antioxidant enzyme activities, tissue damage, and the intestinal microbiome of Opsariichthys bidens were preclinically investigated by detecting the liver’s enzymatic activities, observing hepatointestinal tissue sections, and high-throughput sequencing technology. Doxycycline hydrochloride (DH), neomycin sulfate (NM), and sulfamethoxazole (SD) were selected as representatives of three classes of antibacterial agents and used for testing. The findings indicate that administering treatment doses of DH, NM, and SD for 7 days each led to alterations in the total antioxidant capacity (T-AOC) of O. bidens and triggered oxidative stress, with SD causing a decrease in the activity of superoxide dismutase (SOD). Histological analysis revealed that the three antimicrobials could cause tissue damage; for example, liver cell swelling, infiltration of inflammatory cells, and significant congestion in severe instances. The number of goblet cells in the intestinal mucosal layer increased significantly, the microvilli fell off, and the muscle layer dissolved into bubbles. High-throughput sequencing technology was used to analyze the gut microbiota of O. bidens fed with antibiotics for 14 days, and the three antimicrobials had different observed effects on the abundance and diversity of the intestinal microbiota. NM increased the abundance and diversity of the microbiota, while DH and SD reduced the abundance and increased the diversity of the microbiota. In addition to inhibiting the growth of pathogenic bacteria, these antimicrobials can also promote the growth of abnormal intestinal microbiota (other pathogenic bacteria), therefore, destroying intestinal homeostasis. In conclusion, dietary supplementation with therapeutic doses of antibiotics for O. bidens can cause tissue damage, oxidative stress, and alterations in the abundance and diversity of the intestinal microbiome. This study provides a reference for the scientific use of antibiotics in O. bidens and establishes an important theoretical framework for preventing intestinal homeostatic imbalances.