Historically, b-lactam antibiotics are the most widely used antibiotics in clinical settings around the world (Garau 2005, Boeckel 2014 ESAC 2009, ECDC 2012), but the successful of antibiotic treatments is compromised by the development of resistance in many important clinical pathogens (Davies 2010). The major cause of resistance to b-lactams antibiotics are bacterial enzymes called b-lactamases with the capacity to hydrolyze the molecular structure of the b-lactam antibiotic (Davies 1994). Many studies have assessed the presence and diversity of b-lactamases in clinical settings (Paterson 2005, Rice 2001, Ramphal 2006, Shahid 2014, Sullivan 2015), but no enough efforts have been put in assess b-lactamases in non-clinical settings.

Studies assessing the AR phenomenon in non-clinical environments usually are based on functional metagenomics studies, PCR reactions, MIC tests (Donato 2010, Bhullar 2012, Segawa 2012Amos 2014, Forsberg 2014, Su 2014Ma 2014), but in the last years, the use of metagenomic approaches (Yang 2013,Li 2015Fondi 2016) appear such as an interesting tool to assess ARGs in environmental samples. In this context, the focus on antibiotic resistance genes in natural environments should be considered, specially if we consider the evidence that these genes have a long evolutionary history in natural environments (