PNA Technology - The Backbone Advantage

Peptide nucleic acid (PNA) molecules are DNA mimics in which the negatively charged sugar-phosphate backbone of DNA is replaced with a non-charged polyamide or “peptide” backbone. PNA probes contain the same nucleotide bases as DNA, adenine (A), cytosine (C), guanine (G), and thymine (T) and follow standard Watson-Crick base-pairing rules while hybridizing to complementary nucleic acid sequences.

The synthetic backbone provides PNA probes with unique hybridization characteristics compared to DNA probes. While hybridizing to complementary nucleic acid sequences, DNA probes must overcome a destabilizing electrostatic repulsion between the negatively charged backbones, resulting in slower and weaker binding. Because of the non-charged backbone, PNA probes do not encounter the electrostatic repulsion allowing them to hybridize rapidly and tightly to nucleic acid targets.

Ribosomal RNA Target - Rapid and Specific Hybridization

Growing bacteria and yeast cells produce an abundance of ribosomal RNAs that contain regions of highly conserved, species-specific sequences and are therefore ideal targets for identification assays such as FISH. However, the target sequences are frequently located in highly structured regions of the rRNA which are virtually inaccessible to DNA probes. The unique properties of PNA probes allow access to these regions under conditions optimal for FISH resulting in a simple yet highly sensitive and specific hybridization assay (PNA FISH) suited for rapid and accurate identification of bacteria and yeast.

How It Works - 2.5 Hrs Time to Results

PNA FISH uses fluorescent-labeled PNA probes in a highly sensitive and specific 2.5 hours fluorescence in situ hybridization (FISH) assay targeting the species-specific ribosomal RNA (rRNA) in microbes. Once a blood culture turns positive, a Gram stain is performed and based on the results the appropriate PNA FISH test is selected.

Following the Gram stain result, a drop from the positive blood culture is fixed onto a microscope slide. PNA probe is added and hybridizes to the rRNA within the target microbes (S. aureus, C. albicans, E. faecalis, other enterococci, etc.). Excess probe is removed during a stringent wash step and the slides are visualized using fluorescence microscopy. Fluorescing cells identify the target microbe while non-florescence indicates the presense of a different microbe in the blood culture.