Pressure Ulcers in Patients Receiving Enteral Nutrition Therapy and Their Relationship With Gut Microbiota

Human EGF, human VEGF/human TGF-β1 will be measured on aliquots (20 μl) of plasma using Quantikine® ELISA Human Immunoassay (R&D System, Abingdon, UK), following the manufacturer's protocol. The quantitative sandwich enzyme immunoassay technique will be used. A monoclonal antibody specific for human EGF/human VEGF, is pre-coated onto a microplate. For TGF -β1 assay latent TGF-β1 must be activated before test, following a procedure of acidification and then neutralization to pH 7.2-7.6. Standards and samples are pipetted into the wells and EGF or VEGF present is bound by the immobilized antibody. After washing away unbound substances, an enzyme-linked polyclonal antibody specific for human EGF/human VEGF is added to the wells. After removing any unbound antibody-enzyme reagent, a substrate solution is added and colour develops in proportion to the amount of EGF bound. Colour development is stopped, and colour intensity measured. Tests will be performed in triplicates for each sample.

Total DNA will be extracted in triplicate from all the fecal samples by following the QIAamp DNA Stool Mini Kit instructions (Qiagen) and quantified with a Qubit® 2.0 fluorometer (Invitrogen, USA). Molecular weight and fragment length of DNA will be checked on 1.5 % agarose gel; the yield will be calculated as µg DNA/g feces. Quantitative PCR (qPCR) assays will be conducted using the specific primers rpoB1, rpoB1o and rpoB2 that generate amplicons of 250-bp, on 10 ng DNA templates for all the samples. Amplification will be carried out and three simultaneous replicates will be carried out for each of analyzed sample.