Multilocus variable-number tandem-repeat analysis for molecular typing of Shigella sonnei

Area of Science:

• Microbiology
• Molecular Epidemiology
• Infectious Disease Surveillance

Background:

• Shigella sonnei is a significant cause of bacterial dysentery.
• Accurate subtyping methods are crucial for tracking S. sonnei outbreaks and transmission.
• Pulsed-field gel electrophoresis (PFGE) has been a standard but has limitations in discriminatory power.

Purpose of the Study:

• To develop and evaluate a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) method for S. sonnei subtyping.
• To compare the discriminatory power of MLVA with PFGE.
• To assess the utility of MLVA in outbreak investigations and epidemiological studies.

Main Methods:

• Identification of 26 VNTR loci in S. sonnei genomic sequences.
• Testing of 536 S. sonnei isolates previously characterized by PFGE.
• Evaluation of MLVA performance using isolates from 10 shigellosis outbreaks and 22 PFGE-indistinguishable isolates.

Main Results:

• MLVA demonstrated significantly higher discriminatory power (D=0.9524) than PFGE (D=0.8882).
• MLVA using only 4 or 8 loci achieved discriminatory power close to that of 26 loci.
• MLVA effectively distinguished isolates during outbreak investigations and differentiated PFGE-indistinguishable strains.

Conclusions:

• MLVA is a powerful and highly discriminatory tool for S. sonnei subtyping.
• MLVA exhibits excellent potential to replace PFGE for routine S. sonnei surveillance and outbreak analysis.
• Isolates with MLVA profiles differing by a single locus should be considered part of the same outbreak.