Abundances and key driving factors of combined contaminations of antibiotic resistome and metal resistome in tilapia aquaculture

Abstract

Microbiota carrying antibiotic and metal resistance genes pose increasing threats to human health. The profiles of the abundance and dissemination of the extracellular and intracellular antibiotic resistome (ARO) and metal resistome (MRO) in aquaculture environments and reared organisms, and their interrelationships, intrinsic connections, and driving factors are poorly understood. The purpose of this study was to investigate the changes in the extracellular and intracellular ARO and MRO abundances and their key driving factors during the rearing process in tilapia aquaculture. The results show that the abundance of the ARO was strongly positively correlated with that of the MRO (p < 0.01). The correlation coefficients between the abundances of plasmids and the ARO as well as MRO were 0.93 and 0.97, respectively (p < 0.05). Redundancy analysis (RDA) showed that plasmids were significantly positively correlated with the ARO and MRO in tilapia aquaculture water (p < 0.05), while multivariable linear regression analysis showed that plasmids were significantly and positively correlated with the MRO (p < 0.01). Network analysis and RDA showed that Actinobacteria were significantly positively correlated with ARO and MRO. The results of this study indicate that the extracellular ARO is a preponderant form of and significant contributor to antibiotic resistance. Combined ARO and MRO contamination could be positively driven and exacerbated by plasmids through propagation. The bacterial flora is an intrinsic bridge between the ARO and MRO. Mobile genetic elements, especially plasmids, are key drivers of their spread. Based on the results of this study, we conclude that extracellular antibiotic resistance genes (ARGs) should receive more attention and focus in the control of the propagation of ARGs. The abundances of ARO and MRO in tilapia pond water increased significantly; thus, the aquaculture water of tilapia farming should be treated effectively before discharge to reduce ARO and MRO contamination in the receiving environment.