Florfenicol has been approved by the U.S. Food and Drug Administration to control the infection caused by Edwardsiella ictaluri in catfish. However, there is limited information about the impact of such treatment on the native microbiota associated with catfish. As the microbial composition and abundance in catfish may directly influence the catfish’s health and growth, it is crucial to understand how therapeutical florfenicol treatment impacts the microbial populations associated with catfish and in its rearing waters.
Eight 35-gallon tanks were set up for this study with 25 fish in each tank and hold at 25 °C (a temperature at which ESC typically occurs). Five fish were taken from each tank before and after the treatment as well as at the end of withdrawal period. Microorganisms present on fish gill and skin, and in the intestine were collected by using FLOQSwabs. Their abundance and diversity were analyzed by direct plating and 16S rRNA sequencing
Both total aerobic and anaerobic counts in the intestine significantly (P > 0.05) increased at the end of treatment and continued increasing at the end of withdrawal period. The abundance of bacterial phyla, such as Patescibacteria, Fibrobacterota, and Proteobacteria, present in the intestine of catfish was altered by the florfenicol treatment. Results indicated that the impact of florfenicol on the native microorganisms is site-dependent with bigger impacts observed in the intestine, and the antibiotic treatment could generate prolonged impact on the antimicrobial resistant profiles in catfish (Figure 1). This study provides valuable information on the impact of florfenicol treatment during catfish production, which is needed for ensuring the sustainability of aquaculture production and for improving food safety.