Insights into the relationship between antimicrobial residues and bacterial populations in a hospital-urban wastewater treatment plant system

Abstract

The relationship between antimicrobial residues, antibiotic resistance prevalence and bacterial community composition in hospital effluent and in the receiving wastewater treatment plant was studied. Samples from hospital effluent, raw inflow and final effluent of the receiving wastewater treatment plant were characterized for amoxicillin and ciprofloxacin resistance prevalence, content of heavy metals and antimicrobial residues and bacterial community

Antibiotic resistance in urban aquatic environments: can it be controlled?

“…Since domestic wastewater contains antibiotic residues, it is arguable that such residues can impose selective effects on ARB, although, as discussed above, the low concentrations found in wastewater can make this issue controversial. Some recent reports have assessed possible correlations be-tween antibiotics and metals concentration and the microbiota in wastewater or in freshwater samples (Graham et al 2011;Huerta et al 2013;Novo et al 2013;Narciso-da-Rocha et al 2014;Varela et al 2014;Rodriguez-Mozaz et al 2015). As hypothesized by the authors, these studies showed significant positive correlations between the concentration of antibiotic residues or metals and ARB&ARG or specific bacterial com-munity members in aquatic environments.…”

“…These studies demonstrated that hospital effluents contain higher prevalence of ARGs (e.g., tetW, blaTEM, or sul1), including some genetic determinants which occurrence is mainly related with clinical practices, such as the gene vanA (Varela et al 2013(Varela et al , 2015bNarcisoda-Rocha et al 2014;Rodriguez-Mozaz et al 2015). Hospital effluents can contain higher concentrations of antibiotic residues, metalloids, and metals like arsenic or mercury, and significantly higher abundance of ARB&ARG than municipal effluents (Kümmerer and Henninger 2003;Varela et al 2014;Rodriguez-Mozaz et al 2015). Yet, since hospital effluents can be classified as domes-tic effluents, there is no legal recommendation for pretreatment aiming at reducing the microbial loads before its dis-charge in the municipal collectors.…”

“…Directly or indirectly, these sources may contribute to the enhancement of ARB&ARG, part of which will reach the municipal collector. Indeed, some types of antibiotic residues (e.g., tetracyclines or sulfonamides) and some ARG (such as plasmid mediated quinolone resistance genes of the family qnrS) can be more frequent in municipal wastewater and biosolids than in hospital effluents (Kaplan et al 2013;Varela et al 2014;RodriguezMozaz et al 2015;Varela et al 2016).…”

“…While human medicine, mainly in what concerns antibiotics administration in health care units, tends to use last-generation antibiotics of classes of fluoroquinolones, cephalosporins, or carbapenems, in animal production, "older" antibiotics such as tetracyclines, sulfonamides, or penicillins are preferred (WHO 2014; EFSA/ECDC 2015; Done et al 2015). The use of different antibiotics for animal production and for human medicine may explain the observation of distinct correlations between the bacterial community composition and antibiotic-resistant populations and the concentration in wastewater of tetracyclines, sulfonamides, and penicillins or fluoroquinolones (Novo et al 2013;Varela et al 2014). Nevertheless, it is suggested that both sources of contamination with antibiotic residues are probably associated with antibiotic resistance dissemination and bacterial community disturbance.…”

“…In particular, the complexity of waste-or fresh-water composition in terms of nutrients, particles and microbiota, may make difficult a reliable prediction of the bioavailability of antibiotic residues or of their effects on target bacteria. In spite of these shortcomings, in wastewater, it was possible to demonstrate that the concentration of ciprofloxacin, tetracycline, sulfamethoxazole, or arsenic could be correlated with the prevalence of ARB, the abundance of the genes blaTEM, vanA, or intI1 (related with beta-lactam and vancomycin resistance and class 1 integrons, respectively) or the increase of populations of Bacteroidetes, Clostridia, or Proteobacteria of the classes Gamma or Epsilon (Novo et al 2013;Narciso-da-Rocha et al 2014;Varela et al 2014). Also in surface water and sediments, similar correlations were observed, suggesting that in the environment downstream the wastewater treatment plant, selective pressures may still be exerting some effects.…”