Peptide nucleic acid fluorescence In situ hybridization for rapid detection of Klebsiella pneumoniae from positive blood cultures

This study evaluated a novel peptide nucleic acid (PNA) probe targeting a region of the 23S rRNA gene of Klebsiella pneumoniae by fluorescence in situ hybridization (FISH). Analytical performance was determined using 39 reference strains and other well-characterized strains of Klebsiella spp. and Enterobacter aerogenes. The probe was found to be specific for the K pneumoniae complex (K pneumoniae including Klebsiella ozaenae and Klebsiella variicola). The diagnostic accuracy was evaluated with 264 blood cultures containing Gram-negative rods. Using conventional identification as the reference, performance specifications were as follows: sensitivity 98.8%, specificity 99.5%, positive predictive value 98.8% and negative predictive value 99.5 %. Discrepancies were resolved by PNA FISH retest and phenotypic tests. In conclusion, the K pneumoniae probe provided an accurate diagnosis within 3 In and may supplement other methods for direct identification of Gram-negative bacteria.