Accelerated identification of Staphylococcus aureus from blood cultures by a modified fluorescence in situ hybridization procedure

This study evaluated fluorescence in situ hybridization (FISH) for rapid identification of Staphylococcus aureus and coagulase-negative staphylococci (CoNS) directly from blood cultures. Initially, 360 blood cultures containing Gram-positive cocci were investigated by a previously described microwave-FISH procedure: 44/49 (89.8%) S. aureus and 298/299 (99.7%) CoNS were correctly identified. Because FISH proved useful and reliable but handling was found to be inconvenient, the method was modified by employing a recently developed slide chamber. This reduced the time required from 60 to 30 min. The simplified execution allowed integration of the method into the workflow of a routine laboratory without difficulty. The modified method proved to be highly reliable, identifying 37/37 (100%) S. aureus and 169/172 (98.2%) CoNS directly from blood cultures.