Molecular analysis of clonally related Salmonella Typhi recovered from epidemiologically unrelated cases of typhoid fever, Brazil

• Published in: International journal of infectious diseases 2019-04, Vol.81, p.191-195
• Main Authors: Tiba-Casas, Monique Ribeiro, Sacchi, Cláudio Tavares, Gonçalves, Cláudia Regina, Almeida, Elisabete Aparecida, Soares, Flávia Barrosa, de Jesus Bertani, Amanda Maria, Fernandes, Sueli Aparecida, de Paula Eduardo, Maria Bernadete, Camargo, Carlos Henrique
• Format: Article
• Language: English
• Subjects: Antimicrobial resistance; Phylogenetic; Salmonella Typhi; Whole genome sequencing
• ISSN: 1201-9712; 1878-3511
• DOI: 10.1016/j.ijid.2019.02.009

•This study brings up new information regarding the strengths and drawbacks of WGS using different analytic approaches compared to the traditional typing method, PFGE, for retrospectively typing cluster cases of S. Typhi isolated in São Paulo, Brazil.•Although any exposure factor could be associated with the cases in this study, a common unidentified source probably exists since different laboratorial tests and analysis of WGS identify a common pattern among the contemporary S. Typhi strains recovered from patients with typhoid fever.•In our study, WGS based typing, using ND, SNP analysis and wgMLST, was able to compete with PFGE for outbreak clustering. The performance of the three selected WGS based typing methods was validated based on the clusters of S. Typhi strains. The primary method of molecular subtyping for the identification and investigation of outbreaks has been pulsed-field gel electrophoresis (PFGE). In some cases, this technique has not been able to show discrimination between the unrelated strains that can be achieved by whole genome sequencing (WGS). The aim of this study was to determine the strengths and drawbacks of WGS using different analytic approaches compared to traditional typing method, PFGE, for retrospectively typing clusters cases of 28 S. Typhi. We evaluated three analytical approaches on the WGS data set (Nucleotide Difference (ND), (SNPs) and Whole genome multi locus sequence typing (wgMLST) that identically classified the clusters-related strains into two clusters, cluster A (with strains from 2017), and Cluster B (with strains from 2007). In this study WGS based typing, was able to compete with PFGE for differentiation of the clusters of S. Typhi strains.