Authenticating Anaerobes – Use of MALDI-TOF MS to identify anaerobes in the NCTC Collection

Abstract

The National Collection of Type Cultures (NCTC) is the world’s oldest repository of medically-relevant bacteria. NCTC contains 5,500 bacterial strains, 500 of which are anaerobes, with the collection regularly receiving new Type strains and recent clinical isolates. Fastidious anaerobes pose a unique challenge during the authentication process. NCTC must ensure that the strains are free from contamination and that the organism survives the lyophilisation process. Species-level identification of anaerobic bacterial strains is achieved using a combination of the both MALDI-TOF MS and VITEK2 instruments. This study evaluates the use of MALDI-TOF MS (Bruker) and VITEK2 (BioMerieux) to identify the anaerobic strains in the NCTC collection. 176 NCTC strains were tested on the MALDI-TOF platform and 60 strains were identified using VITEK2. MALDI-TOF was able to identify 79% anaerobes to genus-level and 64% to species-level. In comparison the VITEK2 identified 68% to genus and 46% to species-level. The main limiting factor for both these platforms is the database. This may be due to novel anaerobe species NCTC receives not being present on the databases. In the event of no identification, 16S ribosomal RNA sequencing is employed. Furthermore, detection of specific characteristics is carried out by specialist reference laboratories in Cardiff and Colindale, ensuring a robust collection of anaerobic bacteria for use in research and as control strains.