Microbial typing by matrix-assisted laser desorption ionization-time of flight mass spectrometry: do we need guidance for data interpretation?

The integration of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in clinical microbiology has revolutionized species identification of bacteria, yeasts, and molds. However, beyond straightforward identification, the method has also been suggested to have the potential for subspecies-level or even type-level epidemiological analyses. This minireview explores MALDI-TOF MS-based typing, which has already been performed on many clinically relevant species. We discuss the limits of the method's resolution and we suggest interpretative criteria allowing valid comparison of strain-specific data. We conclude that guidelines for MALDI-TOF MS-based typing can be developed along the same lines as those used for the interpretation of data from pulsed-field gel electrophoresis (PFGE).

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

Conventional 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.

Measuring clinical outcomes of highly multiplex molecular diagnostics for respiratory infections: A systematic review and conceptual framework.

Objectives: To review methodologies and outcomes reporting among these studies and to develop a conceptual framework of outcomes to assist in guiding studies and production of clinical metrics. Data sources: PubMed and Embase from January 1, 2012, thru December 1, 2021. Study eligibility criteria: Studies evaluating highly multiplex molecular respiratory diagnostics and their impact on either clinical or economic outcomes. Methods: A systematic literature review (SLR) of methodologies and outcomes reporting was performed. A qualitative synthesis of identified SLRs and associated primary studies was conducted to develop conceptual framework for outcomes. Results: Ultimately, 4 systemic literature reviews and their 12 associated primary studies were selected for review. Most primary studies included patient outcomes focusing on antimicrobial exposure changes such as antibiotic (80%) and antiviral use (50%) or occupancy changes such as hospital length of stay (60%). Economic outcomes were infrequently reported, and societal outcomes, such as antibiotic resistance impact, were absent from the reviewed literature. Qualitative evidence synthesis of reported outcomes yielded a conceptual framework of outcomes to include operational, patient, economic, and societal domains. Conclusions: Our review highlights the significant heterogeneity in outcomes reporting among clinical impact studies for highly multiplex molecular respiratory diagnostics. Furthermore, we developed a conceptual framework of outcomes domains that may act as a guide to improve considerations in outcomes selection and reporting when evaluating clinical impact of these tests. These improvements may be important in synthesizing the evidence for informing clinical decision making, guidelines, and financial reimbursement.

Streptococcus agalactiae clones infecting humans were selected and fixed through the extensive use of tetracycline.

Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones. The parallel expansion of the clones is preceded by the insertion of integrative and conjugative elements conferring tetracycline resistance (TcR). Thus, we propose that the use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only few TcR clones particularly well adapted to their host, causing the observed emergence of GBS diseases in neonates.