ABSTRACT
Human-made antibiotics, in huge amounts, reach the environment in a number of ways, as overviewed in the previous chapter. This alone is a cause of concern, as the ecological impact of the presence of these natural compounds in unnatural quantities, is hard to assess. However, the problem is worsened by the simultaneous release of resistant bacteria that have been selected by the human use of antibiotics. Again, this is happening at a multi-level, complex scenario that goes, from the seemingly insignificant open defecation of a pet dog receiving antibiotics in an urban setting; to the use of manure from medicated food animals to fertilize soils; to the massive release of untreated sewage into water bodies. These organisms can find their way into our foodstuff and drinking water, directly causing antibiotic-resistant infections; or can, possibly to a larger health risk, contribute their resistance determinants, and mobile genetic elements, to the enormous gene pool available via HGT, to be further selected by the concomitant presence of antibiotics in the environment.
