Peptide nucleic acid–fluorescence in situ hybridization for detection of staphylococci from endophthalmitis isolates: A proof-of-concept study

PURPOSE. Rapid identification of pathogens causing endophthalmitis may improve treatment outcomes through early administration of species-specific medication. The current study reports a new molecular application of peptide nucleic acid–fluorescence in situ hybridization (PNA-FISH) with Staphylococcus-specific molecular PNA probes for the potential rapid detection of common pathogens causing endophthalmitis. METHODS. An experimental study was designed to evaluate the proof of concept at the microbiology laboratory of the Bascom Palmer Eye Institute. Stored culture-positive staphylococci endophthalmitis isolates obtained from prior vitreous samples (n = 15), along with broth as negative controls (n = 5) were used. Inoculum was prepared to a final concentration of 1 × 10⁵ colony-forming units/mL to ensure that the isolates were viable. Smears of samples were fixed and hybridized using QuickFISH protocol with probes for Staphylococcus. RESULTS. With PNA-FISH technique, Staphylococcus aureus was identified in 9 of 10 samples and coagulase-negative staphylococci were identified in 10 of 10 samples. Detection time was 20 minutes. CONCLUSIONS. This study serves a proof of concept using a new microbial detection system with FISH probes, and may have the potential for clinical use in the rapid and accurate identification of isolates from patients with endophthalmitis.