Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 2/16/2007
Publication Date: 5/21/2007
Citation: Dowd, S.E., Lyte, M. 2007. Microarray analysis of Norepinephrine-Escherichia coli O157:H7 gene expression in a porcine ligated ileal loop model and comparison to in vitro data: In vivo veritas? [abstract]. American Society for Microbiology 107th General Meeting, May 21-25, 2007, Toronto, Canada. Abstract No. B-256. Interpretive Summary:
Technical Abstract: The ability of stress-related neurochemicals, such as norepinephrine, to influence bacterial growth and virulence-related properties, termed microbial endocrinology, has been demonstrated by a number of groups. Recent microarray gene analysis has further shown the induction of key virulence factors by norepinephrine. However, while the majority of studies of neuroendocrine-bacterial interactions have utilized in vitro systems, it is not known if similar changes occur in vivo. In order to examine the in vivo ability of norepinephrine to affect virulence gene expression in E. coli O157:H7, we utilized a porcine ligated ileal loop model. E. coli O157:H7 (ATCC 43895) harvested from overnight LB culture was resuspended in a minimal salts medium supplemented with pig serum, incubated 5 hrs at 37 deg C in 5% CO2 environment, and then injected into ileal loops in anesthetized 5 week old female pigs (6 pigs per group). Immediately thereafter, either control (diluent) or norepinephrine (final concentration 500 uM) was injected into loops. Following a 2 hour incubation period in the loops, the loop contents were collected into RNAprotect bacterial reagent and RNA extracted for use in microarray analysis and for subsequent quantitative RT-PCR validation. Results from in vivo data were then compared to that obtained from an in vitro simulation of this study. Using a false discovery rate of <0.05, we found similar regulation of 45 genes in both in vivo and in vitro studies. The most repressed genes included a set of phage shock genes, while induced transcripts included stx1 and stx2. Other induced genes were associated with LPS biosynthesis and iron transport. It can be concluded that norepinephrine-bacterial interactions which have previously been identified in vitro to affect a number of key virulence properties of E. coli O157:H7 also occur in vivo; thereby demonstrating the utility of in vivo model systems, such as the porcine ligated ileal loop, to study the microbial endocrinology of E. coli O157:H7 pathogenesis.