MGTdb: A web service and database for studying the global and local genomic epidemiology of bacterial pathogens

Abstract

Multilevel genome typing (MGT) enables the genomic characterization of bacterial isolates and the relationships among them. The MGT system describes an isolate using multiple multilocus sequence typing (MLST) schemes, referred to as levels. Thus, for a new isolate, sequence types (STs) assigned at multiple precisely defined levels can be used to type isolates at multiple resolutions. The MGT designation for isolates is stable, and assignment is faster than existing approaches. MGTs utility has been demonstrated in multiple species. This paper presents a publicly accessible web service called MGTdb, which enables the assignment of MGT sequence types to isolates, along with their storage, retrieval and analysis. The MGTdb web service enables upload of genome data as sequence reads or alleles, which are processed and assigned MGT identifiers. Additionally, any newly sequenced isolates deposited in NCBI Sequence Read Archive are also regularly retrieved (currently daily), processed, assigned MGT and made publicly available in MGTdb. Interactive visualisation tools are presented to assist analysis, along with capabilities to download publicly available isolates and assignments for use with external software. MGTdb is currently available for Salmonella enterica serovars Typhimurium and Enteritidis, and Vibrio cholerae. We demonstrate the usability of MGTdb through three case studies to study the long-term national surveillance of S. Typhimurium, and the local epidemiology and outbreaks of S. Typhimurium, and the global epidemiology of V. cholerae. Thus, MGTdb enables epidemiological and microbiological investigations at multiple levels of resolution for all publicly available isolates of these pathogens. Database URLhttps://mgtdb.unsw.edu.au