Occurrence, Prevalence, and Disinfection Potential of Tetracycline Resistance Genes and Tetracycline Resistant Bacteria in a Subtropical Watershed

Abstract

Antibiotics are an important method for protecting human health. Unfortunately, the development of antibiotic resistance has decreased the effectiveness of antibiotics in treating disease and preventing deaths associated with bacterial infection. The objective of this dissertation research was to gain a better understanding of anthropogenic influences on occurrence of tetracycline resistance and use of traditional disinfection methods for the reduction of tetracycline resistant bacteria and genes. Culture based and molecular methods were used to evaluate the occurrence of tetracycline resistance in a rapidly urbanizing watershed, identify the dominant resistant organisms and resistance genes in the watershed, and evaluate the use of UV and chlorine to reduce the concentration of resistant bacteria and resistance genes.

Results from this research showed that tetracycline resistance was prevalent and is maintained in this study area. Several bacterial species (Aeromonas, Acinetobacter, Chryseobacterium, E. coli, Pseudomonas, and Serratia) made up the resistant population. The results also indicated that tet(W) was the major resistance gene in this watershed and that a majority of the resistant bacteria were capable of transferring their resistance. Landuse did not cause a difference in occurrence of resistant bacteria or resistance genes which suggests that a rapidly urbanizing watershed could experience resistance. It was also identified that environmental media (sediment and water) influence the occurrence and prevalence of resistant bacteria and resistance genes. The results indicate that streambed sediment may act as a reservoir for resistance and resistance might be transported in the water. Finally, the results showed that neither UV nor chlorine disinfection were effective in reducing tet(W) concentrations though the results varied greatly among species.

Results from this research indicate that preventing the occurrence and distribution of resistance gene in the environment is difficult, and resistance will most likely be maintained. Therefore, in order to prevent the spread of antibiotic resistance, it will be important to prevent antibiotic resistance from becoming established in the environment. This can be done by educating the public about the importance of misusing and mismanaging antibiotics. Additionally, classifying antibiotics for either human or veterinary use may help slow the development of resistance. This should prevent clinically important antibiotics from being used in sub-therapeutic doses, which could decrease the selective pressure in the environment. Also clinically relevant bacteria can be prevented from interacting with resistant bacteria in the environment by disinfecting human waste.