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INTRODUCTION
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Hospital wastewaters are highly complex effluents containing antibiotic compounds, metabolized drugs, disinfectants (Emmanuel et al. 2005), patients' excrement and microorganisms, potentially containing multidrug-resistant (MDR) genes (Chang et al. 2010; Galvin et al. 2010; Chagas et al. 2011). As such, hospital wastewaters are considered as hot spots for antibiotic resistance, generating an environment for the exchange of antibiotic resistance genes. Gram-negative bacteria bearing multiple bla genes (e.g. blaNDM, blaKPC, blaCTX-M, and blaSHV) are increasingly found in hospital wastewaters (Chagas et al. 2011; Zhang et al. 2012). This is consistent with antimicrobial resistance surveillance in Europe 2015 (ECDC 2017), observing an increase in combined resistance to multiple antimicrobial groups, as well as a high proportion of extended spectrum beta-lactamases (ESBL) producing isolates, leaving few treatment alternatives for patients suffering from infections caused by these pathogens. Besides its impact on treatment, frequent resistance in Gram-negative bacteria may lead to an increased use of carbapenems, thus further favouring the emergence and spread of carbapenem-resistant bacteria.
Hospital effluents are discharged as common community wastewater to the wastewater treatment plant (WWTP), with no pre-treatment or cleaning process. After treatment, water is discharged into surfaces waters. Certain pathogenic microorganisms can remain in an aquatic environment for longer periods, creating dissemination routes and environmental reservoirs of antibiotic resistance genes (ARG) (Meirelles-Pereira et al. 2002; Perron et al. 2008). Over the last two decades, the occurrence of antibiotics in water bodies and subsequent development of microbial resistance has come into scientific and public focus as an issue of potential concern (Kümmerer 2009a; Rodríguez-Gil et al. 2010). Hospital wastewaters are one of the sources contributing significantly to the environmental burden of antibiotics and consequently antibiotic resistance (Kümmerer 2004; Zhang et al. 2009; Davies & Davies 2010; Harris et al. 2012). ARGs can be found in almost all environments and they are currently considered as an emerging pollutant and an ecological problem (Kümmerer 2004; Engemann et al. 2008). Environmental ARGs could serve as a reservoir and can be horizontally transferred to human-associated bacteria and thus contribute to antibiotic resistance proliferation (Khan et al. 2013).
The aim of this study was to evaluate the presence of ESBL and carbapenemase producing Enterobacteriaceae in hospital wastewater from one Slovenian and two Austrian hospitals. At the time of...