Detection and quantification of clinically relevant plasmid-mediated AmpC beta-lactamase genes in aquatic systems

The extent and impact of plasmid-mediated AmpC beta-lactamase genes (pAmpCs) prevalence in aquatic environments is poorly understood. The aim of this study was to detect and quantify pAmpCs from the aquatic environment. The following pAmpCs were analysed with clinical TaqMan assays from isolated plasmids: ACC, ACT/MIR, BIL/LAT/CMY, DHA, FOX and MOX/CMY. Quantification was conducted using quantitative PCR (qPCR) and 3D chip-based digital PCR. The results of qPCR yielded 4,875.27 copies/ng DNA and dPCR, 1,640.58 copies/ng (Mann–Whitney U Test, p= 0.868). Redundancy analysis indicated that land coverage explains 90.49% (ANOVA, p= 0.601) of pAmpC variance. There was a correlation between the frequency and quantities of pAmpCs detected in each river and this could be related to anthropogenic influence. Frequencies of detection for pAmpCs were 25/36 for the Crocodile West River and 13/36 for the Marico River. Quantification resulted in higher copy numbers for the Crocodile West River and high copies in only two sites of the Marico River, thus reflecting degrees of anthropogenic influences on both rivers. The presence of these clinically relevant pAmpCs in aquatic systems are cause for concern, considering their potential impact if these genes are harboured by pathogens and become dispersed to human populations.