Rapid identification of Vibrio parahaemolyticus isolated from shellfish, sea water and sediments of the Khnifiss lagoon, Morocco, by MALDI-TOF mass spectrometry.

We establish the presence of Vibrio parahaemolyticus and deepen the comparison of isolates using MALDI-TOF MS for the typing of isolates originating from the Khnifiss lagoon (Morocco). Amongst 48 samples from sea water, sediment and shellfish isolated from different sites of Khnifiss lagoon, Morocco, we obtained 22 isolates of V. parahaemolyticus identified by Vitek 2™ System (bioMérieux) and MALDI Biotyper™ (Bruker Daltonics). All isolates were highly resistant to ampicillin and ticarcillin, moderately resistant to cefalotin, but sensitive to 16 other antimicrobials tested. MALDI-TOF MS was used to discriminate between closely related environmental strains of V. parahaemolyticus. A clustering and distribution based on MALDI-TOF spectra were generated using the BioTyper 1.1™ software. Despite low diversity in regard to the biochemical characteristics and antimicrobial resistance, the isolates evoke a larger biodiversity when analysed through mass spectra of abundant proteins. Different evaluations of a cut-off value showed that, when placed at a 10% threshold of the whole diversity, isolates differed by at least three mass peaks.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry identifies 90% of bacteria directly from blood culture vials.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is now widely used for marker/multi-biomarker detection in medical diagnosis. We tested a new protocol for bacterial identification from blood culture broths in hospital routine by using collection tubes with separator gels on 503 included samples examined over 3 months, where 1.5 mL was injected by a syringe into BD Vacutainer tubes from BACTEC-positive bottles, before processing for bacterial protein extraction. Samples were loaded in duplicate onto the MALDI MS target, allowing a series of 12 samples to be processed in duplicate within 80 min by using Biflex III and BioTyper 2.0 software (Bruker). Including polymicrobial samples, 193 of 213 of Gram-negative bacteria (91.08%) and 284 of 319 of Gram-positive bacteria (89.02%) were correctly identified at the species level. Enterobacteriaceae constituted 35.15% of all species found, Staphylococaceae 37.96%, Streptococaceae and Enterococaceae 20.85%, Pseudomonadaceae 1.69%, and anaerobes 2.44%. In most of the polymicrobial samples, one of the species present was identified (80.9%). Seven isolates remained misidentified as Streptococcus pneumoniae, all belonging to Streptococcus mitis. Staphylococcus aureus was identified better when grown on anaero-aerobic medium, and MALDI BioTyper identification scores as low as 1.4 were pertinent, provided that four successive proposals of the same species were given. This new protocol correlates with conventional microbiology procedures by up to 90%, and by >95% for only monomicrobial samples, and provides a decreased turn-around time for identification of bacteria isolated from blood cultures, making this technology suitable also for blood cultures, with less delay and cost decreases in bacterial diagnostics, and favouring better care of patients.

High interlaboratory reproducibility of matrix-assisted laser desorption ionization-time of flight mass spectrometry-based species identification of nonfermenting bacteria.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry has emerged as a rapid, cost-effective alternative for bacterial species identification. Identifying 60 blind-coded nonfermenting bacteria samples, this international study (using eight laboratories) achieved 98.75% interlaboratory reproducibility. Only 6 of the 480 samples were misidentified due to interchanges (4 samples) or contamination (1 sample) or not identified because of insufficient signal intensity (1 sample).