![]() When satisfactory results were obtained with Gram-negative bacteria, we applied the direct method to monomicrobial blood cultures containing Gram-positive cocci. The results obtained were compared with those by MALDI-TOF and Vitek 2 yielded with bacteria isolated on solid media the day after, further referred to as routine methods. At first, the direct method was applied to blood cultures containing Gram-negative bacteria. In this study, we aimed at establishing a simple, reliable, and accurate method, further referred to as the direct method, using bacteria harvested from blood cultures by serum separator tubes (SST) and placed onto the polished steel target plate for identification by MALDI-TOF, in order to completely integrate the rapid method into the diagnostic routine. However, an easier method reducing the number of steps before the steel target plate of MALDI-TOF is prepared could be a real advantage for many clinical microbiology laboratories. To assess the use of MALDI-TOF for the identification of bacteria recovered from blood cultures, a variety of protocols (series of washes, centrifugations), protein extraction methods and analysis have been proposed. ![]() The MALDI-TOF technology has the potential to be adapted to identify microorganisms grown in biological fluids. However, this method requires that bacteria from positive blood cultures are isolated on solid media, thus delaying bacterial identification by 24 h. With the development of the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry, the time required for accurate identification of microorganisms isolated on solid media to the species level reduced to a few minutes. In addition, several DNA-based techniques, introduced with the aim to replace blood-culture systems technology, resulted to be useful as a complement, but not as a replacement of current automated systems. To shorten the identification process, wide efforts have been made, including concentration of bacteria by centrifugation before direct inoculation of blood culture fluids into automated systems, and fluorescent in situ hybridization. The direct method herein developed allows rapid identification (within 30 min) of Gram-negative bacteria and Gram-positive cocci from positive blood cultures and can be used to rapidly report reliable and accurate results, without requiring skilled personnel or the use of expensive kits.īlood culture is the gold standard to diagnose the causative agent(s) of bloodstream infections. Identification by the SepsiTyper method of Gram-positive cocci gave concordant results with MALDI-TOF on isolated bacteria in 87 % of cases (37 % with score > 2.0). These two methods were 90 % concordant on Gram-positive cocci (32 % with score > 2.0). Identification of Gram-negative bacilli was 100 % concordant using the direct method or MALDI-TOF on isolated bacteria (96 % with score > 2.0). ![]() The results by the direct method were compared with those obtained by MALDI-TOF on bacteria isolated on solid media. Herein, we aimed at establishing an easier and simpler method, further referred to as the direct method, using bacteria harvested by serum separator tubes from positive blood cultures and placed onto the polished steel target plate for rapid identification by MALDI-TOF. Rapid identification of the causative agent(s) of bloodstream infections using the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) methodology can lead to increased empirical antimicrobial therapy appropriateness. ![]()
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