Avian pathogenic Escherichia coli (APEC) cause colibacillosis, an economically devastating disease, which has major impact on this country's poultry industry. Also, there is evidence that APEC, contaminating retail poultry, may be a food-borne source of E. coli causing urinary tract infections and other extraintestinal diseases in human beings. Despite the importance of APEC, little has been known about the mechanisms underlying this organism's abilities to cause disease, resist therapy, and persist in the environment. However, scientists have recently reported that plasmids are widespread among APEC and may be the defining trait of the APEC pathotype. Plasmids are extrachromosomal DNA molecules that are frequently transferred among bacteria during "bacterial sex". APEC plasmids have been shown to possess many of the genes which enable E. coli to cause disease and resist antibiotics and heavy metals, such as those used as disinfectants. The transmissibility of these plasmids and their ubiquity among APEC in the poultry production environment and on retail poultry suggest that these plasmids could serve as a reservoir of "disease-enhancing" genes for other bacterial pathogens, including those causing disease in humans. Unfortunately, scientists' understanding of plasmids' contributions to disease have been hindered by the lack of complete plasmid genomic sequences available and the inadequacies of the tools with which plasmids can be studied.
The present study seeks to remedy these problems by providing high quality sequences of the most common APEC plasmids known, training a new generation of scientists in plasmid sequence analysis, and development of a new E. coli Plasmid Genome Database tool that is available for widespread use for analysis of E. coli plasmids. The immediate objective of this project is to obtain fully annotated genomic sequences of 7 of the most commonly occurring APEC plasmids. These sequences will enable high-throughput functional genomic investigations, accelerate hypothesis-driven research on the pathogenesis of colibacillosis, and provide insight into the role of these plasmids and plasmid transfer in sculpting the genome of APEC and other costly and deadly pathogens. It is thought that the proposed study will enable better understanding of how plasmid transfer can be controlled in the future to the betterment of animal, human, and environmental health. Specifically, the investigators will: 1) construct genomic libraries of 7 APEC plasmids and conduct random shotgun sequencing of each to 8-fold coverage; 2) assemble the draft sequences, close sequence gaps, and resolve ambiguities; 3) annotate all plasmid genomes and compare them to known sequences; 4) train students at Mississippi State University in bioinformatics and genomics; and 5) disseminate information and materials from this project to producers, poultry veterinarians, poultry health researchers, and other scientists with interests in colibacillosis prevention and treatment, plasmids, and the effects of plasmid transfer on development of disease-causing ability and antimicrobial resistance among APEC and other bacterial pathogens.
