Tetracycline Resistance Gene Profiles in Red Seabream (Pagrus major) Intestine and Rearing Water After Oxytetracycline Administration.

Yumiko Obayashi,Aya Kadoya,Satoru Suzuki,Su-Min Bak,Kazuki Kanda,Hisato Iwata,Naoto Kataoka

doi:10.3389/fmicb.2020.01764

Abstract

Marine aquaculture fish and the environment are possible hot spots for the maintenance and spread of antibiotic resistance genes (ARGs). We here show the time courses of changes of six tetracycline resistance genes (tet) in fish rearing seawater and fish intestine in tank experiments. Experimental tanks were prepared as oxytetracycline (OTC) administration tanks and those without OTC. It was found that tet(B), tet(M), and tet(W) were dominant in seawater among the six tet genes. tet(B) and tet(M) abundances increased immediately after OTC administration, indicating that OTC served as a selective pressure to increase the proportion of tet-possessing bacteria. In contrast, the abundance of tet genes in the fish intestine did not differ between the with- and without-OTC administration groups, and clearly was not altered by OTC administration. Profile changing of tet in seawater and fish intestine did not synchronize. These observations suggested that the dynamics of intestinal tet-possessing bacteria do not directly reflect the environment, but reflect selection within the intestine.

Highlights

The prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) has been expanding globally, leading to concern regarding increasing risks to human health (Llor and Bjerrum, 2014)
The detected amounts of tet genes from the rearing water in the control tank could be considered as the background levels for each day, and presumably were derived from a combination of the original seawater inflow and the fish feces. tet(B) and tet(M) are frequently detected in seawater bacteria (Furushita et al, 2003; Kim et al, 2007; Roberts et al, 2012), and tet(W) is known to be present in sediments in rivers and the sea (Suzuki et al, 2008)
Seawater has been reported to serve as a reservoir of Escherichia coli with ARGs that are carried by seagulls (Alves et al, 2014)

Summary

Introduction

The prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) has been expanding globally, leading to concern regarding increasing risks to human health (Llor and Bjerrum, 2014). Oxytetracycline (OTC) has been used historically in aquaculture in many countries to control fish diseases (World Health Organization [WHO], 2006; Cebello et al, 2013). Tetracycline resistance genes (members of the tet series) have been detected in various sites associated with aquaculture, including (for example) sediments beneath net-pens (Tamminen et al, 2011b) and waters close to fish farms (Kim et al, 2004; Suzuki et al, 2019). Environmental bacteria possessing tet(M) have been isolated from seawater and sediments at aquaculture sites where OTC has been administered (Nonaka et al, 2007). The results of Tetracycline Resistance Genes in Seabream studies at aquaculture sites have indicated primarily that tet genes are distributed in seawater and sediment, reflecting transmission between fish and the environment. The literature suggests that ARG dynamics relate to aquaculture activities and the fish under study

Methods

Results

Conclusion