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More Information about Developing Technologies for Tracking Drug Resistant Escherichia coli
Background
Many bacterial, viral, and protozoan pathogens exist in coastal environments and pose a threat to public health. Some of these pathogens, such as Vibrio species and mycobacteria, are indigenous to the oceans. Other agents are introduced to the oceans through fecal material. These foreign microbes include enteric bacteria (e.g. Escherichia coli, Salmonella spp. and Shigella spp.), enteric viruses (e.g., Noroviruses, Hepatitis A and some Caliciviruses), and protozoan parasites (e.g., Cryptosporidium parvum and Giardia lamblia). Foreign microbes enter coastal oceans via agricultural and urban surface runoff, wastewater discharges, storm water drainage systems, and domestic and wild animals. Exposure to these pathogens occurs by consuming either contaminated seafood or seawater, or by exposure of open wounds to contaminated water. Of this group of pathogens, those originating from humans are considered the most immediate public health threat. Whether consumption of the same or similar species originating from either domestic or wild animals are pathogenic to humans is less well understood, though the prevailing wisdom is that these represent a secondary health concern.
The co-occurrence of bacteria originating from multiple sources with varying pathogenicity complicates assessment of public health risks, particularly in the case of bacteria such as Escherichia coli and Salmonella spp. These bacteria are commonly shed by domestic and wild animals as well as humans, and have similar probabilities of being transported into estuarine waters via runoff. This means that if public health risks are to be adequately assessed, some estimate of bacterial origin must be developed. Currently, detection methods for most microorganisms of public health concern are woefully inadequate, with methods for discriminating the origin of specific pathogens being even less developed. The purpose of this research is to investigate whether genetic sequences associated with multiple drug resistance in bacteria can be used to identify those of human origins and for source tracking of human waste contamination in estuarine waters. The model system being used in this study is multiple drug resistant E. coli. The goal of this work is to develop an effective method to track the sources of microbial pollution in order that effective remediation strategies and more accurate risk analyses can be developed.
Multiple-drug-resistant strains of Escherichia coli, originating from humans and domestic animals, were first isolated from estuarine waters in the early 1970s. It was quickly shown that antibiotic resistance was conferred by plasmids, which are autonomous self-replicating pieces of DNA. The high proportion of humans and livestock treated by antibiotics means that significant quantities of antibiotic plasmids are continuously released into the environment. Most individuals now harbor some form of antibiotic resistant bacteria in their digestive tracts. In hospitals, drug resistant bacteria often cause severe illness, which can spread readily among patients. Sensitive molecular assays that target specific antibiotic resistant plasmids have been used to track the spread of these pathogens in hospital settings. Similar assays for tracking these antibiotic resistant pathogens in estuarine environments have yet to be developed. Without these assays it will be difficult to accurately track the sources and spread of these pathogens.