Gram-positive anaerobic cocci (GPAC) account for 24%-31% of the anaerobic bacteria isolated from human clinical specimens. At present, GPAC are under-represented in the Biotyper MALDI-TOF MS database. Profiles of new species have yet to be added. We present the optimization of the matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) database for the identification of GPAC. Main spectral profiles (MSPs) were created for 108 clinical GPAC isolates. Identity was confirmed using 16S rRNA gene sequencing. Species identification was considered to be reliable if the sequence similarity with its closest relative was ≥98.7%. The optimized database was validated using 140 clinical isolates. The 16S rRNA sequencing identity was compared with the MALDI-TOF MS result. MSPs were added from 17 species that were not yet represented in the MALDI-TOF MS database or were under-represented (fewer than five MSPs). This resulted in an increase from 53.6% (75/140) to 82.1% (115/140) of GPAC isolates that could be identified at the species level using MALDI-TOF MS. An improved log score was obtained for 51.4% (72/140) of the strains. For strains with a sequence similarity <98.7% with their closest relative (n = 5) or with an inconclusive sequence identity (n = 4), no identification was obtained by MALDI-TOF MS or in the latter case an identity with one of its relatives. For some species the MSP of the type strain was not part of the confined cluster of the corresponding clinical isolates. Also, not all species formed a homogeneous cluster. It emphasizes the necessity of adding sufficient MSPs of human clinical isolates.

Within the ENRIA project, several 'expertise laboratories' collaborated in order to optimize the identification of clinical anaerobic isolates by using a widely available platform, the Biotyper Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Main Spectral Profiles (MSPs) of well characterized anaerobic strains were added to one of the latest updates of the Biotyper database db6903; (V6 database) for common use. MSPs of anaerobic strains nominated for addition to the Biotyper database are included in this validation. In this study, we validated the optimized database (db5989 [V5 database] + ENRIA MSPs) using 6309 anaerobic isolates. Using the V5 database 71.1% of the isolates could be identified with high confidence, 16.9% with low confidence and 12.0% could not be identified. Including the MSPs added to the V6 database and all MSPs created within the ENRIA project, the amount of strains identified with high confidence increased to 74.8% and 79.2%, respectively. Strains that could not be identified using MALDI-TOF MS decreased to 10.4% and 7.3%, respectively. The observed increase in high confidence identifications differed per genus. For Bilophila wadsworthia, Prevotella spp., gram-positive anaerobic cocci and other less commonly encountered species more strains were identified with higher confidence. A subset of the non-identified strains (42.1%) were identified using 16S rDNA gene sequencing. The obtained identities demonstrated that strains could not be identified either due to the generation of spectra of insufficient quality or due to the fact that no MSP of the encountered species was present in the database. Undoubtedly, the ENRIA project has successfully increased the number of anaerobic isolates that can be identified with high confidence. We therefore recommend further expansion of the database to include less frequently isolated species as this would also allow us to gain valuable insight into the clinical relevance of these less common anaerobic bacteria.

This data in brief article presents the data obtained during the validation of the optimized Biotyper Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) database. The validation was performed by the different expertise laboratories, collaborating within the European Network for the Rapid Identification of Anaerobes (ENRIA) project, using 6309 human clinical anaerobic bacterial strains.Different databases were compared with each other; the db 5989 database (V5 database); the V5 database complimented with Main Spectral Profiles (MSPs) of ENRIA strains added to the next update of the database; and the V5 database complimented with the MSPs of all anaerobic clinical isolates collected within the ENRIA project. For a comprehensive discussion of the full dataset, please see the research article that accompanies this data article (Veloo et al., 2018) [1]

Following the first description of a Clostridium difficile case caused by ribotype 027 in Hungary in 2007, the rapid spread of C. difficile infection in different hospitals within the country was observed. The aim of this pilot study was to investigate the distribution of different PCR ribotypes among inpatient and outpatient isolates obtained in two geographically different parts of Hungary. One hundred and ninety-two toxigenic C. difficile isolates collected between 1 October and 1 December 2014 were PCR ribotyped using capillary gel electrophoresis and the database of WEBRIBO (http://webribo.ages.at), which allows the automatic analysis and comparison of capillary-sequencer-based PCR ribotyping data. Altogether, 31 different known ribotypes were found, and 16 isolates showed a novel banding pattern, not included in the current library. Besides the dominance of 027 (33.3 %) among all isolates, there were differences in its presence among isolates obtained from the two regions (45.8 % in the central region and 20.8 % in the south-east region, respectively), whereas the second most prevalent ribotype 036 (19.8 %) was more frequently found among isolates obtained in the south-east region compared with the central region of Hungary (29.1 versus 10.4 %). Similar differences in the spread of different ribotypes, in particular 027, which were found during earlier studies in Hungary may be due to the existing order for admissions of patients to hospitals. We also summarized the changing pattern of PCR ribotypes of Hungarian C. difficile isolates over time, based on earlier published data.

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