Assessing visitor use impact on antibiotic resistant bacteria and antibiotic resistance genes in soil and water environments of Rocky Mountain National Park.

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been detected in soil and water in close proximity to anthropogenic sources, but the extent to which human impact plays into ARB and ARGs entering the environment is not well described. This study aimed to determine the impact of visitor use on ARB and ARGs in a national park environment. Soil (n = 240) and water (n = 210) samples were collected across a gradient of human activity in Rocky Mountain National Park and analyzed for bacteria resistant to doxycycline, levofloxacin, and vancomycin. Amount of physical effort required to access a sampling site was used as a metric for the likelihood of human presence. A subset of samples was analyzed for the presence and abundance of six ARGs using quantitative polymerase chain reaction. Linear regression analysis demonstrated that anthropogenic factors including hiking effort and proximity to a toilet significantly contributed to the variance of the abundance of ARB for multiple antibiotics in soil and water. Additionally, ecological factors such as water movement, soil texture, and season may play a role in the detection of ARB and ARGs. Predictive analysis suggests that both human presence and human activities, such as waste elimination, significantly contributed to the abundance of ARB in soil and water. The results of this work evidence that the ecology of antibiotic resistance in remote environments is more complex than anthropogenic impact alone, necessitating further environmental characterization of ARB and ARGs.