Antibiotic Resistance Genes Distribution and Relevant Risk Assessment in Karst Caves-Taking Guizhou Shuanghe Cave as an Example

Abstract

Water environment in Shuanghe Cave, a typical karst cave in Guizhou, China, is being contaminated by antibiotics and antibiotic resistance genes (ARGs). Thus, this cave was selected and sampled to assay antibiotics in groundwater, ARGs relative abundance and microoganisms  in sediments. Correlation of ARGs with microorganisms, as well as relevant risk assessment were further analyzed. Results indicated, total concentration of antibiotics in groundwater ranged from 55.81 to 118.65 ng·L -1 ,  among which the highest concentration was OFL, accounting for 34.68 ng L -1 . In sediments, multidrug (44.30%) was the most abundant ARG classes, followed by tetracycline (11.01%) and MLS (9.68%), and the dominant ARG subtypes were macB (5.18%), tetA (58) (3.83%) and rpoB2 (3.11%). At a phylum level, the dominant microorganisms were Proteobacteria (44.60%) and Actinobacteria (27.46%); and at a genus level, the dominant were Nitrospira (1.53%) and Rubrobacter (1.09%). Furthermore, correlation among antibiotics, ARG subtypes and microorganisms showed CTC in water could promote TaeA and optrA expression of Aromatoleum in sediments. Correlation between ARG subtypes  and microorganisms suggested that ARG subtypes  were homegrown products by microorganisms, but foreign ARG subtypes could also affect microbial communities.  Partial least squares path model(PLS-PM) analysis confirmed that water nutrition physicochemical factors and ions could exert effects on antibiotics, and microbial community in sediments could directly affect ARGs. In this cave, OFL was the most dangerous factor, ENR and CTC were at a medium risk, and other antibiotics were at a safe level. According to environmental risk assessment, ARGs and antibiotics were all at a low risk.

Keywords: Karst Cave, Antibiotics, antibiotic resistance genes, Microorganisms, Environmental risk assessment