Date of Award

1-1-2011

Document Type

Campus Access Dissertation

Department

Environmental Health Sciences

First Advisor

Robert S. Norman

Abstract

The impact of antibiotics in the environment constitutes a topic of great concern and research has been conducted throughout the years to determine how these compounds affect public health. Bacterial antibiotic resistance is not a novel phenomenon, however since the mass production of antibiotics in the 1940s, the increased number of bacterial species showing resistance to one or multiple antibiotics reflects the accelerating rate of this process over the years. Furthermore, this phenomenon has led to the reduction of antibiotic efficiency by requiring higher doses to control a disease, and in other cases to restrain the use of certain antibiotics for clinical applications. Two factors that have contributed to the increased rate of antibiotic resistance over the years are the increased overall global population, and the production/use of antibiotics for clinical and agricultural purposes.

Among the continuously increasing population, it has been estimated that more than 40% of the world population lives within 100 km of coastlines. According to the United Nations, in the next decade, population will increase by 14% in these areas. With the increase in the population density, there has been an increase in the use and production of pharmaceuticals. Worldwide, the annual production of antibiotics is estimated to be between 150 to 200 million kg, where 60% is used for clinical purposes and the remaining amount employed for agricultural activities. This trend places a higher pressure on coastal ecosystems in terms of increased wastewater contaminants from runoff and industrial, medical and domestic facilities. Wastewater treatment plants (WWTPs) receive pharmaceutical residues and bacteria from hospitals, small industries and households. Due to the high level of bacterial activity occurring in WWTPs these facilities may support the generation and propagation of antibiotic resistance genes or dissemination elements that may be subsequently released to aquatic ecosystems, transferring resistance to pathogenic and non-pathogenic bacteria. This represents a possible risk for aquatic animals and humans. The purpose of this study was to characterize microbial antibiotic resistance and integrase gene distribution throughout a wastewater treatment facility and a heavily populated coastal estuarine ecosystem using culture independent methodologies to determine their ultimate fate in the environment. Results indicated the presence of a highly resistance gene blaM-1 conferring resistance to ampicillin (MIC: 384-448 ppm), and three classes of integrase genes potentially involved in horizontal gene transfer. The WWTP examined in this study discharges an average of 136 million L day-1 of treated wastewater, which represents approximately 3.9 x 10^14 GCN of blaM-1, and 2.4 x 10^13, 2.7 x 10^13, and 1.0 x 10^14 GCNs of IntI1, IntI2, and IntI3, respectively released every day into the surrounding ecosystem. Different geographical patterns of distribution were observed for blaM-1 and IntI genes in environmental samples. Results generated from this research may be used to provide a better knowledge of how an urban landscape might be affecting the evolution of surrounding microbial communities. Furthermore, this study examines the potential of WWTPs to act as environmental reservoirs of antibiotic resistant traits that are subsequently disseminated into surrounding environments.

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