Optimization of the preanalytical steps of matrix-assisted laser desorption ionization-time of flight mass spectrometry identification provides a flexible and efficient tool for identification of clinical yeast isolates in medical laboratories

International audienceWe report here that modifications of the preanalytical steps of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identification of yeasts, with regard to the original protocol provided by the manufacturers, appear to be efficient for the reliable routine identification of clinical yeast isolates in medical laboratories. Indeed, when one colony was sampled instead of five and the protein extraction protocol was modified, the performance of MALDI-TOF MS was superior to that of the API ID 32C method (discrepancies were confirmed by using molecular identification), allowing the correct identification of 94% of the 335 clinical isolates prospectively tested. We then demonstrated that the time for which the primary cultures were preincubated on CHROMagar did not impact the identification of yeasts by MALDI-TOF MS, since 95.1 and 96.2% of the 183 clinical yeast isolates prospectively tested were correctly identified after 48 and 72 h of preincubation, respectivel

Rapid Identification of Candida glabrata Based on Trehalose and Sucrose Assimilation Using Rosco Diagnostic Tablets

We developed a simple method for the identification of Candida glabrata on the basis of the ability of this species to rapidly assimilate trehalose but not sucrose. After incubation of yeasts with Rosco diagnostic tablets containing sucrose or trehalose, identification of C. glabrata was achieved in 4 h with 100% sensitivity and specificity

Evaluation of MALDI-TOF mass spectrometry for the identification of medically-important yeasts in the clinical laboratories of Dijon and Lille hospitals

EA MERSInternational audienceConventional identification (CI) of yeasts is based on morphological, biochemical and/or immunological methods. Matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF or MT-MS) mass spectrometry has been proposed as a new method for the identification of microorganisms. This prospective study compared the performance of MT-MS and CI for the identification of yeasts isolated from clinical samples. Sequencing of the internal transcribed spacer (ITS) regions of ribosomal DNA was used as the reference method in the analysis of a total of 1207 yeast isolates. Concordance between MT-MS and CI was observed for 1105 isolates (91.5%), while 74 isolates (6.1%) were misidentified. Molecular identification revealed that 73 of these 74 isolates were identified correctly by MT-MS and CI correctly identified the last one. Concordance between the two techniques was excellent for the medically-important species (98-100%), including the identification of closely-related species (Candida albicans/C. dubliniensis; C. inconspicua/C. norvegensis; C. parapsilosis/C. metapsilosis/C. orthopsilosis). Only 2.3% of isolates belonging to C. famata, C. lambica and C. magnoliae or to Geotrichum spp. and Trichosporon spp. were not identified by MT-MS. This investigation highlights the potential of MT-MS-based yeast identification as a reliable, time and cost-efficient alternative to CI

Genotyping of Candida albicans Oral Strains from Healthy Individuals by Polymorphic Microsatellite Locus Analysis

Analysis of a polymorphic microsatellite locus was applied to 85 Candida albicans strains from healthy individuals. Comparison with strains from nonhealthy individuals previously analyzed in our laboratory showed an overall similarity, suggesting that all commensal strains have the ability to develop as pathogens

Dynamique de la colonisation fongique dans un nouveau laboratoire de mycologie médicale

International audienceObjective of the study. - Study of the spatio-temporal fungal colonization in a new medical mycology laboratory. Methods. - A 17-month survey of airborne fungal contamination was conducted in a new medical mycology laboratory at a tertiary care university hospital. This survey was implemented at three different periods: before the new premises were occupied (period A), during the move into the new laboratory (period B) and after resumption of the mycological activities in these new premises (period C). Results. - During period A, the airborne fungal load ranged from 2.3 to 6 cfu/m(3). The most frequently recovered airborne fungi were Penicillium spp. (75 to 100%). During period B, a dramatic increase in Penicillium chrysogenum conidia was observed in the air of the new laboratory (40 to 160 cfu/m(3)). During period C, the fungal load ranged from 4.5 to 8.4 cfu/m(3). Penicillium was the most common genus identified in rooms of the laboratory where no filamentous fungi were handled, while Aspergillus was clearly the predominant genus (78%) in the room dedicated to the culture of filamentous fungi. Conclusions. - We suggest that the specific fungal ecology in air of the room dedicated to the culture of filamentous fungi is due to the handling of a large number of medical strains of A. fumigatus.Objectif de l’étude : Étude spatio-temporelle de la colonisation fongique dans un nouveau laboratoire de mycologie médicale. Méthodes : Durant 17 mois, l’aérocontamination fongique a été évaluée dans trois pièces d’un nouveau laboratoire de mycologie médicale d’un centre hospitalo-universitaire. Cette surveillance a été programmée à trois périodes différentes : avant l’occupation des nouveaux locaux (période A), durant l’emménagement dans le nouveau laboratoire (période B) et après la reprise des activités de mycologie médicale dans ces nouveaux locaux (période C). Résultats : Durant la période A, la charge fongique dans l’air était comprise entre 2,3 et 6 ufc/m3. Le micromycète le plus fréquemment isolé a été Penicillium spp. (75 à 100 %). Durant la période B, une très forte augmentation de la charge en conidies de Penicillium chrysogenum a été observée dans l’air du nouveau laboratoire (40 à 160 ufc/m3). Durant la période C, la charge fongique a été comprise entre 4,5 et 8,4 ufc/m3. Penicillium a été le genre le plus fréquemment identifié dans les deux pièces du laboratoire où aucun champignon filamenteux n’est manipulé, alors qu’Aspergillus a clairement été le genre prédominant (78 %) dans la pièce consacrée à la culture des champignons filamenteux. Conclusions : Nous suggérons que la manipulation d’un grand nombre de souches médicales d’Aspergillus est à l’origine de l’écologie spécifique qui existe dans la pièce du laboratoire destinée à la manipulation des champignons filamenteux

Hydro-contamination fongique par Fusarium spp. en milieu hospitalier pendant une période de construction

National audienc

A prospective survey of air and surface fungal contamination in a medical mycology laboratory at a tertiary care university hospital

International audienceBACKGROUND: Invasive filamentous fungi infections resulting from inhalation of mold conidia pose a major threat in immunocompromised patients. The diagnosis is based on direct smears, cultural symptoms, and culturing fungi. Airborne conidia present in the laboratory environment may cause contamination of cultures, resulting in false-positive diagnosis. Baseline values of fungal contamination in a clinical mycology laboratory have not been determined to date. METHODS: A 1-year prospective survey of air and surface contamination was conducted in a clinical mycology laboratory during a period when large construction projects were being conducted in the hospital. Air was sampled with a portable air system impactor, and surfaces were sampled with contact Sabouraud agar plates. The collected data allowed the elaboration of Shewhart graphic charts. RESULTS: Mean fungal loads ranged from 2.27 to 4.36 colony forming units (cfu)/m(3) in air and from 0.61 to 1.69 cfu/plate on surfaces. CONCLUSIONS: Strict control procedures may limit the level of fungal contamination in a clinical mycology laboratory even in the context of large construction projects at the hospital site. Our data and the resulting Shewhart graphic charts provide baseline values to use when monitoring for inappropriate variations of the fungal contamination in a mycology laboratory as part of a quality assurance program. This is critical to the appropriate management of the fungal risk in hematology, cancer and transplantation patients