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- Human health implications of clinically relevant bacteria in wastewater habitatsPublication . Varela, Ana Rita; Manaia, Célia M.The objective of this review is to reflect on the multiple roles of bacteria in wastewater habitats with particular emphasis on their harmful potential for human health. Indigenous bacteria promote a series of biochemical and metabolic transformations indispensable to achieve wastewater treatment. Some of these bacteria may be pathogenic or harbour antibiotic resistance or virulence genes harmful for human health. Several chemical contaminants (heavy metals, disinfectants and antibiotics) may select these bacteria or their genes. Worldwide studies show that treated wastewater contain antibiotic resistant bacteria or genes encoding virulence or antimicrobial resistance, evidencing that treatment processes may fail to remove efficiently these bio-pollutants. The contamination of the surrounding environment, such as rivers or lakes receiving such effluents, is also documented in several studies. The current state of the art suggests that only some of antibiotic resistance and virulence potential in wastewater is known. Moreover, wastewater habitats may favour the evolution and dissemination of new resistance and virulence genes and the emergence of new pathogens. For these reasons, additional research is needed in order to obtain a more detailed assessment of the long-term effects of wastewater discharges. In particular, it is important to measure the human and environmental health risks associated with wastewater reuse.
- Insights into the relationship between antimicrobial residues and bacterial populations in a hospital-urban wastewater treatment plant systemPublication . Varela, Ana Rita; André, Sandra; Nunes, Olga C.; Manaia, Célia M.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 structure, based on 16S rRNA gene PCR-DGGE analysis. The concentration of fluoroquinolones, arsenic and mercury was in general higher in hospital effluent than in raw inflow, while the opposite was observed for tetracyclines, sulfonamides and penicillin G. The prevalence of ciprofloxacin resistance was significantly higher in hospital effluent than in raw inflow. The concentration of antimicrobial residues was observed to be significantly correlated with the prevalence of antibiotic resistant bacteria and with variations in the bacterial community. Hospital effluent was confirmed as a relevant, although not unique, source of antimicrobial residues and antibiotic resistant bacteria to the wastewater treatment plant. Moreover, given the high loads of antibiotic residues and antibiotic resistant bacteria that may occur in hospital effluents, these wastewater habitats may represent useful models to study and predict the impact of antibiotic residues on bacterial communities.