Abstract
The study quantified the abundances of antibiotic resistance genes (ARGs) and facultative pathogenic bacteria (FPB) as well as one mobile genetic element in genomic DNA via qPCR from 23 different wastewater treatment plant (WWTP) effluents in Germany. 12 clinically relevant ARGs were categorized into frequently, intermediately, and rarely occurring genetic parameters of communal wastewaters. Taxonomic PCR quantifications of five FPB targeting Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, and enterococci were performed. The WWTPs differed in their catchment areas being impacted by hospitals, food processing companies, or housing areas only. The total discharges of the analyzed ARGs and FPB were found to cluster independently of the sizes of the WWTPs with a maximum difference of two log units within one cluster. Initially, quantitative data evaluations revealed no significant difference between ARG categories and WWTP catchment areas. More distinct correlations became obvious with a Pearson correlation approach, where each single taxonomic marker is compared to each ARG target. Here, increased correlation of FPB (i.e. E. coli, K. pneumoniae, P. aeruginosa, and enterococci) with clinically relevant ARGs of the category of rarely occurring resistance genes (blaNDM-1, vanA) was found in WWTP effluents being influenced by hospital wastewaters.
Highlights
The increase in infections caused by antibiotic resistant bacteria (ARB) is depicted to be one of the most important issues for the healthcare system of the 21th century[1]
This study focused on the detection of living facultative pathogenic bacteria (FPB) and antibiotic resistance genes (ARGs) of intact bacteria by excluding free DNA and ARG from injured or dead bacteria by living/dead discrimination to emphasize on the possible risk of subsequent human colonization by contact with these waters released to the environment
Due to the use of reference bacteria carrying the respective antibiotic resistance gene for calculation of the abundances of ARB derived from genomic DNA of microbial communities in the water samples, the term “cell equivalents” is used. (Fig. 1)
Summary
The increase in infections caused by antibiotic resistant bacteria (ARB) is depicted to be one of the most important issues for the healthcare system of the 21th century[1]. Because WWTPs are not designed to eliminate ARGs and ARBs, the finale discharge into the receiving water is a key mechanism by which ARGs and ARB enter the aquatic environment[9] This is most critical because the wide spread of ARGs in allochthonous bacteria and horizontal gene transfer events can promote clinically relevant antibiotic resistance in pathogenic bacteria[10]. The accumulation of ARGs, promoting multi-resistant pathogens, makes antibiotic treatment especially difficult This development is dangerous in clinical settings, within the repetitive antibiotic application and insufficient hygiene enhancing the dissemination of ARB. Beside the overall discharge calculations, target-specific Pearson correlations were performed to identify a possible impact of the different catchment sites To our knowledge, this is the first study evaluating an increased number of WWTP effluents with different catchment areas in 12 clinically relevant categories of ARGs and five FPB according to their daily discharge quantities and qualities
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