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Determining antimicrobial susceptibility in Salmonella enterica serovar Typhimurium through whole genome sequencing: a comparison against multiple phenotypic susceptibility testing methods.

Published version
Peer-reviewed

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Authors

Mensah, Nana 
Tang, Yue 
Cawthraw, Shaun 
AbuOun, Manal 
Fenner, Jackie 

Abstract

BACKGROUND: UK public health organisations perform routine antimicrobial susceptibility tests (ASTs) to characterise the potential for antimicrobial resistance in Salmonella enterica serovars. Genetic determinants of these resistance mechanisms are detectable by whole genome sequencing (WGS), however the viability of WGS-based genotyping as an alternative resistance screening tool remains uncertain. We compared WGS-based genotyping, disk diffusion and agar dilution to the broth microdilution reference AST for 102 Salmonella enterica serovar Typhimurium (S. Typhimurium) isolates across 11 antimicrobial compounds. RESULTS: Genotyping concordance, interpreted using epidemiological cut-offs (ECOFFs), was 89.8% (1007/1122) with 0.83 sensitivity and 0.96 specificity. For seven antimicrobials interpreted using Salmonella clinical breakpoints, genotyping produced 0.84 sensitivity and 0.88 specificity. Although less accurate than disk diffusion (0.94 sensitivity, 0.93 specificity) and agar dilution (0.83 sensitivity, 0.98 specificity), genotyping performance improved to 0.89 sensitivity and 0.97 specificity when two antimicrobials with relatively high very major error rates were excluded (streptomycin and sulfamethoxazole). CONCLUSIONS: An 89.8% concordance from WGS-based AST predictions using ECOFF interpretations suggest that WGS would serve as an effective screening tool for the tracking of antimicrobial resistance mechanisms in S. Typhimurium. For use as a standalone clinical diagnostic screen, further work is required to reduce the error rates for specific antimicrobials.

Description

Keywords

Agar dilution, Antimicrobial susceptibility tests, Broth microdilution, Disk diffusion, Salmonella enterica serovar typhimurium, Whole genome sequencing, Anti-Bacterial Agents, Drug Resistance, Multiple, Bacterial, Genome, Bacterial, Genotype, Humans, Microbial Sensitivity Tests, Phenotype, Salmonella enterica, Salmonella typhimurium, Sensitivity and Specificity, Serogroup, Whole Genome Sequencing

Journal Title

BMC Microbiol

Conference Name

Journal ISSN

1471-2180
1471-2180

Volume Title

19

Publisher

Springer Science and Business Media LLC