Microorganisms direct identification from blood culture by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Authors

  • L. Ferreira,

    1. Unidad de Investigación, Hospital Universitario de Salamanca
    Search for more papers by this author
    • These authors contributed equally to this work.

  • F. Sánchez-Juanes,

    1. Unidad de Investigación, Hospital Universitario de Salamanca
    Search for more papers by this author
    • These authors contributed equally to this work.

  • I. Porras-Guerra,

    1. Departamento de Microbiología, Hospital Universitario de Salamanca
    Search for more papers by this author
  • M. I. García-García,

    1. Departamento de Microbiología, Hospital Universitario de Salamanca
    Search for more papers by this author
  • J. E. García-Sánchez,

    1. Departamento de Microbiología, Hospital Universitario de Salamanca
    2. Departamento de Medicina Preventiva, Salud Pública y Microbiología Médica, Universidad de Salamanca, Salamanca, Spain
    Search for more papers by this author
  • J. M. González-Buitrago,

    1. Unidad de Investigación, Hospital Universitario de Salamanca
    2. Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca
    Search for more papers by this author
    • These authors contributed equally to this work and should also be considered as senior authors.

  • J. L. Muñoz-Bellido

    1. Departamento de Microbiología, Hospital Universitario de Salamanca
    2. Departamento de Medicina Preventiva, Salud Pública y Microbiología Médica, Universidad de Salamanca, Salamanca, Spain
    Search for more papers by this author
    • These authors contributed equally to this work and should also be considered as senior authors.


Corresponding author:J. L. Muñoz-Bellido, Departamento de Microbiología, Hospital Universitario de Salamanca, Pº de San Vicente 58-184, 37007 Salamanca, Spain
E-mail: jlmubel@usal.es

Abstract

Clin Microbiol Infect 2011; 17: 546–551

Abstract

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows a fast and reliable bacterial identification from culture plates. Direct analysis of clinical samples may increase its usefulness in samples in which a fast identification of microorganisms can guide empirical treatment, such as blood cultures (BC). Three hundred and thirty BC, reported as positive by the automated BC incubation device, were processed by conventional methods for BC processing, and by a fast method based on direct MALDI-TOF MS. Three hundred and eighteen of them yield growth on culture plates, and 12 were false positive. The MALDI-TOF MS-based method reported that no peaks were found, or the absence of a reliable identification profile, in all these false positive BC. No mixed cultures were found. Among these 318 BC, we isolated 61 Gram-negatives (GN), 239 Gram-positives (GP) and 18 fungi. Microorganism identifications in GN were coincident with conventional identification, at the species level, in 83.3% of BC and, at the genus level, in 96.6%. In GP, identifications were coincident with conventional identification in 31.8% of BC at the species level, and in 64.8% at the genus level. Fungaemia was not reliably detected by MALDI-TOF. In 18 BC positive for Candida species (eight C. albicans, nine C. parapsilosis and one C. tropicalis), no microorganisms were identified at the species level, and only one (5.6%) was detected at the genus level. The results of the present study show that this fast, MALDI-TOF MS-based method allows bacterial identification directly from presumptively positive BC in a short time (<30 min), with a high accuracy, especially when GN bacteria are involved.

Ancillary