Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) was used for an extensive identification study of arthroconidial yeasts using 85 reference strains from the CBS-KNAW Yeast Collection and 134 clinical isolates collected from medical centers in Qatar, Greece and Romania. The test set included 72 strains of ascomycetous (Galactomyces, Geotrichum, Saprochaete and Magnusiomyces spp.) and 147 strains of basidiomycetous (Trichosporon and Guehomyces spp.) taxa. With minimal preparation time, MALDI-TOF/MS proved to be an excellent diagnostic tool that provided reliable identification of most (98 %) of the tested strains to the species level with good discriminatory power. The majority of strains was correctly identified at the species level with good scores (>2.0) and seven of the tested strains with log-values ranging 2.0>score>1.7. The obtained MALDI-TOF/MS results were consistent with validated ITS and/or LSU ribosomal DNA sequences. Further expansion of the mass spectra database by increasing the number of reference strains of closely related species, including those of non-clinical origin, will enhance the usefulness of MALDI-TOF/MS-based diagnostics of these arthroconidial fungi in medical and other laboratories.

Background.

Assessing the CMV specific cell-mediated immunity (CMI) represents an appealing strategy to detect transplant recipients at risk of infection. In this study we compared two interferon gamma-releasing assays (IGRAs), CMV Quantiferon and CMV ELISPOT, in predicting protective CMV specific T-cell responses.Methods.221 Quantiferon and ELISPOT tests were conducted on 120 adult KTR (including 100 R+ and 20 D+/R-). As control cohort 39 adult healthy subjects (including 33 CMV seropositive and 6 CMV seronegative) were enrolled. CMV IgG serology was used as reference for both tests.

Results.

In CMV seropositive individuals, ELISPOT and Quantiferon provided 46% concordance with serology, 12% discordance, 18% disagreement between ELISPOT or Quantiferon with serology and 24% grey areas when one or both tests resulted weak positive. None of CMV seronegative subjects showed detectable responses in ELISPOT and Quantiferon. In transplant recipients, both ELISPOT and Quantiferon positively correlated with each other and negatively correlated to CMV DNAemia in a significant way (p-value <0.05). During the antiviral prophylaxis, all 20 D+/R- KTRs examined displayed undetectable Quantiferon and ELISPOT and there was no evidence of CMV seroconversion. The ROC statistical analysis revealed similar specificity and sensitivity in predicting detectable viremia (AUC 0.66 and 0.62 for Quantiferon and ELISPOT respectively). ELISPOT and Quantiferon values above 150 spots/200000 PBMCs and <1-6 IU IFN-g were associated with protection from CMV infection (OR 5 and 8.75 respectively).

Conclusion.

In transplants both tests displayed similar ability in predicting CMV infection. Both ELISPOT and Quantiferon require several ameliorations to avoid false nagative results.

Although rapid laboratory tests are available for diagnosis of Clostridium difficile infection (CDI), delays in completion of CDI testing are common in clinical practice. We conducted a cohort study of 242 inpatients tested for CDI to determine the timing of different steps involved in diagnostic testing and to identify modifiable factors contributing to delays in diagnosis. The average time from test order to test result was 1.8 days (range, 0.2 to 10.6), with time from order to stool collection accounting for most of the delay (mean, 1.0 day, range 0 to 10). Several modifiable factors contributed to delays, including not providing stool collection supplies to patients in a timely fashion, rejection of specimens due to incorrect labeling or leaking from the container, and holding samples in the laboratory for batch processing. Delays in testing contributed to delays in initiation of treatment for patients diagnosed with CDI and to frequent prescription of empirical CDI therapy for patients with mild to moderate symptoms whose testing was ultimately negative. An intervention that addressed several easily modified factors contributing to delays resulted in a significant decrease in the time required to complete CDI testing. These findings suggest that healthcare facilities may benefit from a review of their processes for CDI testing to identify and address modifiable factors that contribute to delays in diagnosis and treatment of CDI.

We report the first comparative evaluation between the Bruker Biotyper MS (BMS) and the Vitek MS (VMS) for the identification of yeasts. Correct identification rate at the species level was comparable using the commercial databases (89.8% vs. 84.3% p=0.712), but higher for BMS using an in-house-extended database (100% vs. 84.3% p=0.245). Importantly, the rate of misidentification was significantly higher for VMS (1% vs. 12.1% p<0.0001), including the rate of major errors (0% vs. 4.5% p=0.0036).