Universidade do Minho. Centro de Engenharia Biológica (CEB)
Abstract
Peptide nucleic acid (PNA) molecules are DNA mimics, where the negatively charged sugarphosphate
backbone is replaced by an achiral, neutral polyamide backbone formed by
repetitive units of N–(2-aminoethyl) glycine. Due to their superior hybridization properties,
PNA probes to detect pathogens by fluorescence in situ hybridization (FISH) have been
challenging DNA probes over the last few years. In our lab, we have already designed and
developed several new probes for the specific detection of bacterial species such as
Helicobacter pylori, Cronobacter spp., Staphylococcus epidermidis, Salmonella spp. and
Proteus spp. [1, 2]. During development and validation, probes are tested against several
related species, and have been shown to be highly specific for the microorganisms of
interest. All techniques were optimized in slides and then adapted for different types of
samples, depending on the microorganism: H. pylori probe has been developed to work on
gastric biopsies and will soon be tested in a clinical trial for a potentially commercial
application; Cronobacter spp. is a major contaminant of milk-based powdered infant formula,
and as such a probe to detect the pathogen after pre-enrichment of contaminated milk was
devised; S. epidermidis, which is frequently present on the skin of humans, had methods
developed for its identification in blood samples and catheters; and analysis of interest for
Salmonella and Proteus spp. included pipes of drinking water distribution systems and
urinary samples. Future work with PNA probes will involve simultaneous detection of several
species in a single sample and quantitative signal detection by flow cytometry
