Development and evaluation of a multiple-locus variable-number tandem-repeats analysis assay for subtyping Salmonella Typhi strains from sub-Saharan Africa

J Med Microbiol. 2017 Jul;66(7):937-945. doi: 10.1099/jmm.0.000526. Epub 2017 Jul 19.

Abstract

Purpose: Molecular epidemiological investigations of the highly clonal Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) are important in outbreak detection and in tracking disease transmission. In this study, we developed and evaluated a multiple-locus variable-number tandem-repeats (VNTR) analysis (MLVA) assay for characterization of S. Typhi isolates from sub-Saharan Africa.

Methodology: Twelve previously reported VNTR loci were evaluated and an MLVA assay consisting of five polymorphic loci was adopted. The MLVA assay was developed for use on capillary electrophoresis systems by testing a collection of 50 S. Typhi isolates. This S. Typhi strain panel consisted of six outbreak related isolates and 44 epidemiologically unlinked isolates. Amongst these were nine S.Typhi haplotype H58 isolates.

Results: The MLVA assay characterized the 50 isolates into 47 MLVA profiles while PFGE analysis of the same isolates revealed 34 pulsotypes. MLVA displayed higher discriminatory power (Simpson's index of diversity (DI) 0.998 [95 % confidence interval (CI) 0.995-1.000)] as compared to pulsed-field gel electrophoresis [Simpson's DI 0.984 (95 % CI 0.974-0.994)].

Conclusion: The MLVA assay presented in this study is a simple, rapid and more accessible tool that serves as a good alternative to other molecular subtyping methods for S. Typhi.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Africa South of the Sahara / epidemiology
  • Humans
  • Minisatellite Repeats*
  • Molecular Epidemiology / methods*
  • Molecular Typing / methods*
  • Salmonella typhi / classification*
  • Salmonella typhi / genetics*
  • Salmonella typhi / isolation & purification
  • Sensitivity and Specificity
  • Typhoid Fever / epidemiology
  • Typhoid Fever / microbiology*