# Effects of Florfenicol on Intestinal Structure, Microbial Community and Antibiotic Resistance Genes in Penaeus vannamei

## TL;DR

This study examines how the antibiotic florfenicol affects shrimp intestinal health, gut microbes, and antibiotic resistance genes in both shrimp and their environment.

## Contribution

The study reveals how prolonged use of florfenicol alters shrimp gut microbiota and increases antibiotic resistance risks.

## Key findings

- Intestinal damage worsened with longer florfenicol exposure and partially recovered after withdrawal.
- Florfenicol changed microbial diversity in both shrimp and rearing water, increasing harmful bacteria.
- Rearing water may act as a reservoir for spreading antibiotic resistance genes.

## Abstract

Antibiotic feeding in shrimp farming is an optional practice conducted with the aim of preventing and controlling bacterial diseases. However, the administration of antibiotics can disrupt the microbiota of both shrimp and surrounding environment, potentially compromising host health. Given the limited effective antibiotic options in aquaculture, it is crucial to evaluate the effects of florfenicol (FF) on the intestinal health of shrimp and the associated microbial communities. This study first investigated the impact of FF on the intestinal structure of Penaeus vannamei over two feeding durations (5 and 10 days), each followed by a 10-day basal diet recovery period. Simultaneously, variations in microbial communities and antibiotic resistance genes (ARGs) in both the intestine and rearing water were explored. The results showed that intestinal damage was aggravated with the extension of FF duration and gradually recovered after FF withdrawal. Significant changes in microbial composition and β-diversity were observed in both the rearing water and intestine following FF feeding. Extending the FF treatment to 10 days led to a reduced abundance of Rhodobacteraceae and an increased abundance of Flavobacteriaceae and Vibrionaceae in the intestine after 10 days of feeding the basic diet, which may pose a potential risk to shrimp health. Based on correlation analysis of ARGs, microbial communities and pathogenic bacteria, we speculated that rearing water may serve as a reservoir for ARGs dissemination compared to the shrimp intestine. These findings are of great importance for assessing the impact of administration duration under the FF therapeutic dose and highlight the potential risks associated with its overuse in shrimp farming.