Submitted to: Biomed Central (BMC) Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2006
Publication Date: 3/15/2006
Citation: Dowd, S.E., Ishizaki, H. 2006. Microarray based comparison of two Escherichia coli O157:H7 lineages. BioMed Central Microbiology. 6:30. Interpretive Summary: There may be two separate groups of the pathogenic Escherichia coli known as O157:H7. This is the pathogen that is considered one of the primary food borne pathogens in the United States. One of these groups may not be as dangerous to humans as the other, and if this is the case, then it might be possible to determine through molecular genetic methods how they differ. If we can determine why one group is less pathogenic we may be able to use these differences to develop novel treatments to reduce the effects of this pathogen as a food safety risk. To accomplish this, we have utilized the cutting edge microarray technology which is able to evaluate at one time 610 of the genetic factors that are known to contribute to virulence. We have found a number of differences in how these two lineages control their genomes. In this study, we report these findings which include a lower expression of urease genes, shiga toxin genes, and various genes involved in attachment of the pathogen to host cells. These findings, we hope, will lead us to the development of novel methods for control and treatment of these food borne pathogens.
Technical Abstract: Previous research has identified the potential for the existence of two separate lineages of Escherichia coli O157:H7. Clinical isolates tended to cluster with only one of these two lineages. To determine if there are common genes differentially expressed between the two lineages, we chose to utilize microarray technology to perform an initial screening. Using a 610 gene microarray designed against the E. coli O157 EDL 933 transcriptome targeting primarily virulence systems, we chose at random 3 Lineage I isolates (groups clinical and field isolates) and 3 Lineage II isolates (groups field isolates). Using standard dye swap experimental designs, differential regulation of 73 genes between the two lineages was revealed (P < 0.05). Results indicate that under in vitro anaerobic growth conditions as would typically be encountered in a host, there is up-regulation of stx2, urease, curli, and stress pathways in Lineage I, which may contribute to enhanced virulence. Lineage II exhibits significant up-regulation of LPS and flagella related transcripts. The results provide insight and potential direction for future research related to the study of differential virulence in these lineages.