Infection with avian pathogenic E. coli (APEC) is the most common reason for use of antibiotics in poultry production. APEC gives rise to colibacillosis: an umbrella term covering a range of different diseases including colisepticeamia, aerosacculitis, polyserositis, peritonitis and salpingitis, all which causes huge economic losses in the production system and reduced animal welfare. Even though E. coli is arguably the most studied organism in the entire domain of bacteria, we still know surprisingly little of how this bacterium behaves inside the host. Here we examine the metabolic changes E. coli undergoes when transitioning from in vitro into a salpingitis infection. This was done by obtaining the proteome of an APEC strain (F149H1salp2, ST117 O33:H4) during induced salpingitis, with the aims to characterize the relative change of proteins during infection compared to proteome of pathogenic E.coli grown in control media.
By combining a reducing agent and a number of enzymes, we successfully purified and enriched bacteria from mucus of the oviduct in quantities enough for LC-MS based quantitative proteome analysis (using TMT isobaric labelling tags). Since avian derived proteins were in high abundance, we mixed TMT labeled peptides from E.coli proteins derived from the same strain grown in culture media to burst the signal of peptides derived from bacterial proteins from the in vivo samples. Using this approach, we were able to identify over 2000 bacterial proteins and quantified approx. 1500 of them across all the samples. This presentation will detail the major observations on difference in the metabolism between the in vitro and in vivo condition. This experiment demonstrates that it is possible to obtain bacterial in vivo proteome from infected tissue, and our method is deemed applicable to other pathogens and types of tissue.