Aquatic animals promote antibiotic resistance gene dissemination in water via conjugation: Role of different regions within the zebra fish intestinal tract, and impact on fish intestinal microbiota

Abstract

The aqueous environment is one of many reservoirs of antibiotic resistance genes (ARGs). Fish, as important aquatic animals which possess ideal intestinal niches for bacteria to grow and multiply, may ingest antibiotic resistance bacteria from aqueous environment. The fish gut would be a suitable environment for conjugal gene transfer including those encoding antibiotic resistance. However, little is known in relation to the impact of ingested ARGs or antibiotic resistance bacteria (ARB) on gut microbiota. Here, we applied the cultivation method, qPCR, nuclear molecular genetic marker and 16S rDNA amplicon sequencing technologies to develop a plasmid-mediated ARG transfer model of zebrafish. Furthermore, we aimed to investigate the dissemination of ARGs in microbial communities of zebrafish guts after donors carrying self-transferring plasmids that encode ARGs were introduced in aquaria. On average, 15% of faecal bacteria obtained ARGs through RP4-mediated conjugal transfer. The hindgut was the most important intestinal region supporting ARG dissemination, with concentrations of donor and transconjugant cells almost 25 times higher than those of other intestinal segments. Furthermore, in the hindgut where conjugal transfer occurred most actively, there was remarkable upregulation of the mRNA expression of the RP4 plasmid regulatory genes, trbBp and trfAp. Exogenous bacteria seem to alter bacterial communities by increasing Escherichia and Bacteroides species, while decreasing Aeromonas compared with control groups. We identified the composition of transconjugants and abundance of both cultivable and uncultivable bacteria (the latter accounted for 90.4%-97.2% of total transconjugants). Our study suggests that aquatic animal guts contribute to the spread of ARGs in water environments.

Evaluation of Gentamicin Exposure Effects on Human gut Microbiota using the Simulator of Human Intestinal Microbial Ecosystem (SHIME)

“…Most of the intestinal bacteria are not cultivable for the moment, tracking the special gene-labeled plasmid from the exogenous bacteria would help obtain the direct evidence of the horizontal transfer of ARGs in the intestinal ora. There are only a few research reports applying the exogenous labeled bacteria to study the transfer of ARGs among intestinal bacteria [15][16][17]. One study labeled two E. coli strains isolated from human gut and poultry meat, and con rmed the transfer of exogenous plasmid to indigenous bacteria by in vitro intestinal model [15].…”

“…Another paper assessed whether the residual levels of tetracycline affect the integrity of epithelial cells through in vitro cultivation methods, using the translocation of gfp gene-labeled bacteria from the intestinal apical to basal comportment as an indicator [16]. The exogenous bacterium selected in this study was kindly presented by Professor Junwen Li and Zhigang Qiu, who investigated the colonization of this strain in the gut of aquatic model organism zebra sh [17]. In their study, after stopping the addition of exogenous labeled bacteria, the concentrations of exogenous strain and plasmid showed a downward trend, which was in agree with our results.…”

“…Escherichia coli K12Td-Tomato:RK2(EGFP) was the exogenous bacterium used in this study with the Td-Tomato gene genetically integrated into the genome and the Enhanced-gfp (Egfp) gene inserted into the plasmid [17]. This exogenous bacterium was kindly presented by Professor Junwen Li and Zhigang Qiu, Academy of Military Sciences PLA China.…”

Effects of Jerusalem artichoke powder on the growth performance, nonspecific immunity, and gastrointestinal microbiota of sea cucumber

“…Antibiotics are widely used as feed supplementation, and their widespread use has led to the suppression of the immune system of sea cucumbers. The use of antibiotics has also led to increased instances of antibiotic‐resistant bacteria in the culture conditions, which may transfer their resistance genes to other pathogenic bacteria that can infect humans and other animals (Fu et al, ; Ji et al, ). In order to improve culture conditions and ensure the sustainability of sea cucumbers in aquatic production, an improved health management approach needs to be developed.…”

Enzymatic Profiling and Feeding Preferences of Catla: Catla catla, Rohu: Labeo rohita and Mrigala: Cirrhinus mrigala in Rural Polyculture Ponds

“…Previous works have studied the native microflora of aquaculture fish for various objectives. These include microbial spoilage mechanisms, the environmental relationship with fish microflora [18][19][20] and profiling of the indigenous microflora antibiotic resistance [21][22][23].…”