PNA FISH uses fluorescent-labeled PNA [peptide nucleic acid] 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.

Source: medGadget