**4. Non-Aquatic and Aquatic Environment Combined**

While there are studies which look into only one of the many non-aquatic or aquatic compartments of the environment, there are many studies that cover both these types encompassing a composite environment. For example, water and plants [28], water and sand [24], wastewaters, natural and drinking waters and solid matrices such as sludge, sediment, and soil [8,29].

#### **5. Resistance Built up in Bacteria after Exposure to Antibiotics in Environment**

While in vitro studies show a link between antibiotic exposure and antibiotic resistance, experiments are also needed to be done in actual environmental niches to see whether resistance gets built up in the presence of antibiotics in an environmental compartment and whether antibiotic exposure causes any adverse effects on the environmental system. Two such experiments are cited here. In one experiment, in a turkey farm, it was found that resistance to enrofloxacin was detected at a very high frequency after treatments with enrofloxacin via drinking water, a representation of poultry drinking water from natural sources contaminated with antibiotic residues [30]. In another hydroponic experiment, representing plants growing in antibiotic contaminated waters, exposing pakchoi (*Brassica chinensis* L.) to antibiotic contaminated waters, resulted in detection of target antibiotics at concentrations ranging from 6.9 to 48.1 <sup>μ</sup>g·kg−<sup>1</sup> in the vegetable grown in contaminated water, and the rates of antibiotic-resistant endophytic bacteria as well as the resistance genes significantly increased in the plants [31].
